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pull/27/merge
Simon Riggs 8 years ago
parent d204ef6377
commit 83454e3c2b
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  1. 603
      doc/src/sgml/ref/merge.sgml
  2. 575
      src/backend/executor/nodeMerge.c
  3. 660
      src/backend/parser/parse_merge.c
  4. 22
      src/include/executor/nodeMerge.h
  5. 19
      src/include/parser/parse_merge.h
  6. 97
      src/test/isolation/expected/merge-delete.out
  7. 84
      src/test/isolation/expected/merge-insert-update.out
  8. 106
      src/test/isolation/expected/merge-match-recheck.out
  9. 213
      src/test/isolation/expected/merge-update.out
  10. 51
      src/test/isolation/specs/merge-delete.spec
  11. 52
      src/test/isolation/specs/merge-insert-update.spec
  12. 79
      src/test/isolation/specs/merge-match-recheck.spec
  13. 132
      src/test/isolation/specs/merge-update.spec
  14. 1673
      src/test/regress/expected/merge.out
  15. 1173
      src/test/regress/sql/merge.sql

603
doc/src/sgml/ref/merge.sgml
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<!--
doc/src/sgml/ref/merge.sgml
PostgreSQL documentation
-->
<refentry id="sql-merge">
<refmeta>
<refentrytitle>MERGE</refentrytitle>
<manvolnum>7</manvolnum>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>MERGE</refname>
<refpurpose>insert, update, or delete rows of a table based upon source data</refpurpose>
</refnamediv>
<refsynopsisdiv>
<synopsis>
MERGE INTO <replaceable class="parameter">target_table_name</replaceable> [ [ AS ] <replaceable class="parameter">target_alias</replaceable> ]
USING <replaceable class="parameter">data_source</replaceable>
ON <replaceable class="parameter">join_condition</replaceable>
<replaceable class="parameter">when_clause</replaceable> [...]
where <replaceable class="parameter">data_source</replaceable> is
{ <replaceable class="parameter">source_table_name</replaceable> |
( source_query )
}
[ [ AS ] <replaceable class="parameter">source_alias</replaceable> ]
and <replaceable class="parameter">when_clause</replaceable> is
{ WHEN MATCHED [ AND <replaceable class="parameter">condition</replaceable> ] THEN { <replaceable class="parameter">merge_update</replaceable> | <replaceable class="parameter">merge_delete</replaceable> } |
WHEN NOT MATCHED [ AND <replaceable class="parameter">condition</replaceable> ] THEN { <replaceable class="parameter">merge_insert</replaceable> | DO NOTHING }
}
and <replaceable class="parameter">merge_insert</replaceable> is
INSERT [( <replaceable class="parameter">column_name</replaceable> [, ...] )]
[ OVERRIDING { SYSTEM | USER } VALUE ]
{ VALUES ( { <replaceable class="parameter">expression</replaceable> | DEFAULT } [, ...] ) | DEFAULT VALUES }
and <replaceable class="parameter">merge_update</replaceable> is
UPDATE SET { <replaceable class="parameter">column_name</replaceable> = { <replaceable class="parameter">expression</replaceable> | DEFAULT } |
( <replaceable class="parameter">column_name</replaceable> [, ...] ) = ( { <replaceable class="parameter">expression</replaceable> | DEFAULT } [, ...] )
} [, ...]
and <replaceable class="parameter">merge_delete</replaceable> is
DELETE
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
<command>MERGE</command> performs actions that modify rows in the
<replaceable class="parameter">target_table_name</replaceable>,
using the <replaceable class="parameter">data_source</replaceable>.
<command>MERGE</command> provides a single <acronym>SQL</acronym>
statement that can conditionally <command>INSERT</command>,
<command>UPDATE</command> or <command>DELETE</command> rows, a task
that would otherwise require multiple procedural language statements.
</para>
<para>
First, the <command>MERGE</command> command performs a join
from <replaceable class="parameter">data_source</replaceable> to
<replaceable class="parameter">target_table_name</replaceable>
producing zero or more candidate change rows. For each candidate change
row the status of <literal>MATCHED</literal> or <literal>NOT MATCHED</literal> is set
just once, after which <literal>WHEN</literal> clauses are evaluated
in the order specified. If one of them is activated, the specified
action occurs. No more than one <literal>WHEN</literal> clause can be
activated for any candidate change row.
</para>
<para>
<command>MERGE</command> actions have the same effect as
regular <command>UPDATE</command>, <command>INSERT</command>, or
<command>DELETE</command> commands of the same names. The syntax of
those commands is different, notably that there is no <literal>WHERE</literal>
clause and no tablename is specified. All actions refer to the
<replaceable class="parameter">target_table_name</replaceable>,
though modifications to other tables may be made using triggers.
</para>
<para>
When <literal>DO NOTHING</literal> action is specified, the source row is
skipped. Since actions are evaluated in the given order, <literal>DO
NOTHING</literal> can be handy to skip non-interesting source rows before
more fine-grained handling.
</para>
<para>
There is no MERGE privilege.
You must have the <literal>UPDATE</literal> privilege on the column(s)
of the <replaceable class="parameter">target_table_name</replaceable>
referred to in the <literal>SET</literal> clause
if you specify an update action, the <literal>INSERT</literal> privilege
on the <replaceable class="parameter">target_table_name</replaceable>
if you specify an insert action and/or the <literal>DELETE</literal>
privilege on the <replaceable class="parameter">target_table_name</replaceable>
if you specify a delete action on the
<replaceable class="parameter">target_table_name</replaceable>.
Privileges are tested once at statement start and are checked
whether or not particular <literal>WHEN</literal> clauses are activated
during the subsequent execution.
You will require the <literal>SELECT</literal> privilege on the
<replaceable class="parameter">data_source</replaceable> and any column(s)
of the <replaceable class="parameter">target_table_name</replaceable>
referred to in a <literal>condition</literal>.
</para>
<para>
MERGE is not supported if the <replaceable
class="parameter">target_table_name</replaceable> has
<literal>RULES</literal> defined on it.
See <xref linkend="rules"/> for more information about <literal>RULES</literal>.
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><replaceable class="parameter">target_table_name</replaceable></term>
<listitem>
<para>
The name (optionally schema-qualified) of the target table to merge into.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">target_alias</replaceable></term>
<listitem>
<para>
A substitute name for the target table. When an alias is
provided, it completely hides the actual name of the table. For
example, given <literal>MERGE foo AS f</literal>, the remainder of the
<command>MERGE</command> statement must refer to this table as
<literal>f</literal> not <literal>foo</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">source_table_name</replaceable></term>
<listitem>
<para>
The name (optionally schema-qualified) of the source table, view or
transition table.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">source_query</replaceable></term>
<listitem>
<para>
A query (<command>SELECT</command> statement or <command>VALUES</command>
statement) that supplies the rows to be merged into the
<replaceable class="parameter">target_table_name</replaceable>.
Refer to the <xref linkend="sql-select"/>
statement or <xref linkend="sql-values"/>
statement for a description of the syntax.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">source_alias</replaceable></term>
<listitem>
<para>
A substitute name for the data source. When an alias is
provided, it completely hides whether table or query was specified.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">join_condition</replaceable></term>
<listitem>
<para>
<replaceable class="parameter">join_condition</replaceable> is
an expression resulting in a value of type
<type>boolean</type> (similar to a <literal>WHERE</literal>
clause) that specifies which rows in the
<replaceable class="parameter">data_source</replaceable>
match rows in the
<replaceable class="parameter">target_table_name</replaceable>.
</para>
<warning>
<para>
Only columns from <replaceable class="parameter">target_table_name</replaceable>
that attempt to match <replaceable class="parameter">data_source</replaceable>
rows should appear in <replaceable class="parameter">join_condition</replaceable>.
<replaceable class="parameter">join_condition</replaceable> subexpressions that
only reference <replaceable class="parameter">target_table_name</replaceable>
columns can only affect which action is taken, often in surprising ways.
</para>
</warning>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">when_clause</replaceable></term>
<listitem>
<para>
At least one <literal>WHEN</literal> clause is required.
</para>
<para>
If the <literal>WHEN</literal> clause specifies <literal>WHEN MATCHED</literal>
and the candidate change row matches a row in the
<replaceable class="parameter">target_table_name</replaceable>
the <literal>WHEN</literal> clause is activated if the
<replaceable class="parameter">condition</replaceable> is
absent or is present and evaluates to <literal>true</literal>.
If the <literal>WHEN</literal> clause specifies <literal>WHEN NOT MATCHED</literal>
and the candidate change row does not match a row in the
<replaceable class="parameter">target_table_name</replaceable>
the <literal>WHEN</literal> clause is activated if the
<replaceable class="parameter">condition</replaceable> is
absent or is present and evaluates to <literal>true</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">condition</replaceable></term>
<listitem>
<para>
An expression that returns a value of type <type>boolean</type>.
If this expression returns <literal>true</literal> then the <literal>WHEN</literal>
clause will be activated and the corresponding action will occur for
that row. The expression may not contain functions that possibly performs
writes to the database.
</para>
<para>
A condition on a <literal>WHEN MATCHED</literal> clause can refer to columns
in both the source and the target relation. A condition on a
<literal>WHEN NOT MATCHED</literal> clause can only refer to columns from
the source relation, since by definition there is no matching target row.
Only the system attributes from the target table are accessible.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">merge_insert</replaceable></term>
<listitem>
<para>
The specification of an <literal>INSERT</literal> action that inserts
one row into the target table.
The target column names can be listed in any order. If no list of
column names is given at all, the default is all the columns of the
table in their declared order.
</para>
<para>
Each column not present in the explicit or implicit column list will be
filled with a default value, either its declared default value
or null if there is none.
</para>
<para>
If the expression for any column is not of the correct data type,
automatic type conversion will be attempted.
</para>
<para>
If <replaceable class="parameter">target_table_name</replaceable>
is a partitioned table, each row is routed to the appropriate partition
and inserted into it.
If <replaceable class="parameter">target_table_name</replaceable>
is a partition, an error will occur if one of the input rows violates
the partition constraint.
</para>
<para>
Column names may not be specified more than once.
<command>INSERT</command> actions cannot contain sub-selects.
</para>
<para>
The <literal>VALUES</literal> clause can only refer to columns from
the source relation, since by definition there is no matching target row.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">merge_update</replaceable></term>
<listitem>
<para>
The specification of an <literal>UPDATE</literal> action that updates
the current row of the <replaceable
class="parameter">target_table_name</replaceable>.
Column names may not be specified more than once.
</para>
<para>
Do not include the table name, as you would normally do with an
<xref linkend="sql-update"/> command.
For example, <literal>UPDATE tab SET col = 1</literal> is invalid. Also,
do not include a <literal>WHERE</literal> clause, since only the current
row can be updated. For example,
<literal>UPDATE SET col = 1 WHERE key = 57</literal> is invalid.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">merge_delete</replaceable></term>
<listitem>
<para>
Specifies a <literal>DELETE</literal> action that deletes the current row
of the <replaceable class="parameter">target_table_name</replaceable>.
Do not include the tablename or any other clauses, as you would normally
do with an <xref linkend="sql-delete"/> command.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">column_name</replaceable></term>
<listitem>
<para>
The name of a column in the <replaceable
class="parameter">target_table_name</replaceable>. The column name
can be qualified with a subfield name or array subscript, if
needed. (Inserting into only some fields of a composite
column leaves the other fields null.) When referencing a
column, do not include the table's name in the specification
of a target column.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>OVERRIDING SYSTEM VALUE</literal></term>
<listitem>
<para>
Without this clause, it is an error to specify an explicit value
(other than <literal>DEFAULT</literal>) for an identity column defined
as <literal>GENERATED ALWAYS</literal>. This clause overrides that
restriction.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>OVERRIDING USER VALUE</literal></term>
<listitem>
<para>
If this clause is specified, then any values supplied for identity
columns defined as <literal>GENERATED BY DEFAULT</literal> are ignored
and the default sequence-generated values are applied.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>DEFAULT VALUES</literal></term>
<listitem>
<para>
All columns will be filled with their default values.
(An <literal>OVERRIDING</literal> clause is not permitted in this
form.)
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">expression</replaceable></term>
<listitem>
<para>
An expression to assign to the column. The expression can use the
old values of this and other columns in the table.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>DEFAULT</literal></term>
<listitem>
<para>
Set the column to its default value (which will be NULL if no
specific default expression has been assigned to it).
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Outputs</title>
<para>
On successful completion, a <command>MERGE</command> command returns a command
tag of the form
<screen>
MERGE <replaceable class="parameter">total-count</replaceable>
</screen>
The <replaceable class="parameter">total-count</replaceable> is the total
number of rows changed (whether inserted, updated, or deleted).
If <replaceable class="parameter">total-count</replaceable> is 0, no rows
were changed in any way.
</para>
</refsect1>
<refsect1>
<title>Execution</title>
<para>
The following steps take place during the execution of
<command>MERGE</command>.
<orderedlist>
<listitem>
<para>
Perform any BEFORE STATEMENT triggers for all actions specified, whether or
not their <literal>WHEN</literal> clauses are activated during execution.
</para>
</listitem>
<listitem>
<para>
Perform a join from source to target table.
The resulting query will be optimized normally and will produce
a set of candidate change row. For each candidate change row
<orderedlist>
<listitem>
<para>
Evaluate whether each row is MATCHED or NOT MATCHED.
</para>
</listitem>
<listitem>
<para>
Test each WHEN condition in the order specified until one activates.
</para>
</listitem>
<listitem>
<para>
When activated, perform the following actions
<orderedlist>
<listitem>
<para>
Perform any BEFORE ROW triggers that fire for the action's event type.
</para>
</listitem>
<listitem>
<para>
Apply the action specified, invoking any check constraints on the
target table.
However, it will not invoke rules.
</para>
</listitem>
<listitem>
<para>
Perform any AFTER ROW triggers that fire for the action's event type.
</para>
</listitem>
</orderedlist>
</para>
</listitem>
</orderedlist>
</para>
</listitem>
<listitem>
<para>
Perform any AFTER STATEMENT triggers for actions specified, whether or
not they actually occur. This is similar to the behavior of an
<command>UPDATE</command> statement that modifies no rows.
</para>
</listitem>
</orderedlist>
In summary, statement triggers for an event type (say, INSERT) will
be fired whenever we <emphasis>specify</emphasis> an action of that kind. Row-level
triggers will fire only for the one event type <emphasis>activated</emphasis>.
So a <command>MERGE</command> might fire statement triggers for both
<command>UPDATE</command> and <command>INSERT</command>, even though only
<command>UPDATE</command> row triggers were fired.
</para>
<para>
You should ensure that the join produces at most one candidate change row
for each target row. In other words, a target row shouldn't join to more
than one data source row. If it does, then only one of the candidate change
rows will be used to modify the target row, later attempts to modify will
cause an error. This can also occur if row triggers make changes to the
target table which are then subsequently modified by <command>MERGE</command>.
If the repeated action is an <command>INSERT</command> this will
cause a uniqueness violation while a repeated <command>UPDATE</command> or
<command>DELETE</command> will cause a cardinality violation; the latter behavior
is required by the <acronym>SQL</acronym> Standard. This differs from
historical <productname>PostgreSQL</productname> behavior of joins in
<command>UPDATE</command> and <command>DELETE</command> statements where second and
subsequent attempts to modify are simply ignored.
</para>
<para>
If a <literal>WHEN</literal> clause omits an <literal>AND</literal> clause it becomes
the final reachable clause of that kind (<literal>MATCHED</literal> or
<literal>NOT MATCHED</literal>). If a later <literal>WHEN</literal> clause of that kind
is specified it would be provably unreachable and an error is raised.
If a final reachable clause is omitted it is possible that no action
will be taken for a candidate change row.
</para>
</refsect1>
<refsect1>
<title>Notes</title>
<para>
The order in which rows are generated from the data source is indeterminate
by default. A <replaceable class="parameter">source_query</replaceable>
can be used to specify a consistent ordering, if required, which might be
needed to avoid deadlocks between concurrent transactions.
</para>
<para>
There is no <literal>RETURNING</literal> clause with <command>MERGE</command>.
Actions of <command>INSERT</command>, <command>UPDATE</command> and <command>DELETE</command>
cannot contain <literal>RETURNING</literal> or <literal>WITH</literal> clauses.
</para>
<tip>
<para>
You may also wish to consider using <command>INSERT ... ON CONFLICT</command> as an
alternative statement which offers the ability to run an <command>UPDATE</command>
if a concurrent <command>INSERT</command> occurs. There are a variety of
differences and restrictions between the two statement types and they are not
interchangeable.
</para>
</tip>
</refsect1>
<refsect1>
<title>Examples</title>
<para>
Perform maintenance on CustomerAccounts based upon new Transactions.
<programlisting>
MERGE CustomerAccount CA
USING RecentTransactions T
ON T.CustomerId = CA.CustomerId
WHEN MATCHED THEN
UPDATE SET Balance = Balance + TransactionValue
WHEN NOT MATCHED THEN
INSERT (CustomerId, Balance)
VALUES (T.CustomerId, T.TransactionValue);
</programlisting>
notice that this would be exactly equivalent to the following
statement because the <literal>MATCHED</literal> result does not change
during execution
<programlisting>
MERGE CustomerAccount CA
USING (Select CustomerId, TransactionValue From RecentTransactions) AS T
ON CA.CustomerId = T.CustomerId
WHEN NOT MATCHED THEN
INSERT (CustomerId, Balance)
VALUES (T.CustomerId, T.TransactionValue)
WHEN MATCHED THEN
UPDATE SET Balance = Balance + TransactionValue;
</programlisting>
</para>
<para>
Attempt to insert a new stock item along with the quantity of stock. If
the item already exists, instead update the stock count of the existing
item. Don't allow entries that have zero stock.
<programlisting>
MERGE INTO wines w
USING wine_stock_changes s
ON s.winename = w.winename
WHEN NOT MATCHED AND s.stock_delta > 0 THEN
INSERT VALUES(s.winename, s.stock_delta)
WHEN MATCHED AND w.stock + s.stock_delta > 0 THEN
UPDATE SET stock = w.stock + s.stock_delta;
WHEN MATCHED THEN
DELETE;
</programlisting>
The wine_stock_changes table might be, for example, a temporary table
recently loaded into the database.
</para>
</refsect1>
<refsect1>
<title>Compatibility</title>
<para>
This command conforms to the <acronym>SQL</acronym> standard.
</para>
<para>
The DO NOTHING action is an extension to the <acronym>SQL</acronym> standard.
</para>
</refsect1>
</refentry>

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/*-------------------------------------------------------------------------
*
* nodeMerge.c
* routines to handle Merge nodes relating to the MERGE command
*
* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/executor/nodeMerge.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/htup_details.h"
#include "access/xact.h"
#include "commands/trigger.h"
#include "executor/execPartition.h"
#include "executor/executor.h"
#include "executor/nodeModifyTable.h"
#include "executor/nodeMerge.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
#include "utils/builtins.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/tqual.h"
/*
* Check and execute the first qualifying MATCHED action. The current target
* tuple is identified by tupleid.
*
* We start from the first WHEN MATCHED action and check if the WHEN AND quals
* pass, if any. If the WHEN AND quals for the first action do not pass, we
* check the second, then the third and so on. If we reach to the end, no
* action is taken and we return true, indicating that no further action is
* required for this tuple.
*
* If we do find a qualifying action, then we attempt to execute the action.
*
* If the tuple is concurrently updated, EvalPlanQual is run with the updated
* tuple to recheck the join quals. Note that the additional quals associated
* with individual actions are evaluated separately by the MERGE code, while
* EvalPlanQual checks for the join quals. If EvalPlanQual tells us that the
* updated tuple still passes the join quals, then we restart from the first
* action to look for a qualifying action. Otherwise, we return false meaning
* that a NOT MATCHED action must now be executed for the current source tuple.
*/
static bool
ExecMergeMatched(ModifyTableState *mtstate, EState *estate,
TupleTableSlot *slot, JunkFilter *junkfilter,
ItemPointer tupleid)
{
ExprContext *econtext = mtstate->ps.ps_ExprContext;
bool isNull;
List *mergeMatchedActionStates = NIL;
HeapUpdateFailureData hufd;
bool tuple_updated,
tuple_deleted;
Buffer buffer;
HeapTupleData tuple;
EPQState *epqstate = &mtstate->mt_epqstate;
ResultRelInfo *saved_resultRelInfo;
ResultRelInfo *resultRelInfo = estate->es_result_relation_info;
ListCell *l;
TupleTableSlot *saved_slot = slot;
if (mtstate->mt_partition_tuple_routing)
{
Datum datum;
Oid tableoid = InvalidOid;
int leaf_part_index;
PartitionTupleRouting *proute = mtstate->mt_partition_tuple_routing;
/*
* In case of partitioned table, we fetch the tableoid while performing
* MATCHED MERGE action.
*/
datum = ExecGetJunkAttribute(slot, junkfilter->jf_otherJunkAttNo,
&isNull);
Assert(!isNull);
tableoid = DatumGetObjectId(datum);
/*
* If we're dealing with a MATCHED tuple, then tableoid must have been
* set correctly. In case of partitioned table, we must now fetch the
* correct result relation corresponding to the child table emitting
* the matching target row. For normal table, there is just one result
* relation and it must be the one emitting the matching row.
*/
leaf_part_index = ExecFindPartitionByOid(proute, tableoid);
resultRelInfo = proute->partitions[leaf_part_index];
if (resultRelInfo == NULL)
{
resultRelInfo = ExecInitPartitionInfo(mtstate,
mtstate->resultRelInfo,
proute, estate, leaf_part_index);
Assert(resultRelInfo != NULL);
}
}
/*
* Save the current information and work with the correct result relation.
*/
saved_resultRelInfo = resultRelInfo;
estate->es_result_relation_info = resultRelInfo;
/*
* And get the correct action lists.
*/
mergeMatchedActionStates =
resultRelInfo->ri_mergeState->matchedActionStates;
/*
* If there are not WHEN MATCHED actions, we are done.
*/
if (mergeMatchedActionStates == NIL)
return true;
/*
* Make tuple and any needed join variables available to ExecQual and
* ExecProject. The target's existing tuple is installed in the scantuple.
* Again, this target relation's slot is required only in the case of a
* MATCHED tuple and UPDATE/DELETE actions.
*/
if (mtstate->mt_partition_tuple_routing)
ExecSetSlotDescriptor(mtstate->mt_existing,
resultRelInfo->ri_RelationDesc->rd_att);
econtext->ecxt_scantuple = mtstate->mt_existing;
econtext->ecxt_innertuple = slot;
econtext->ecxt_outertuple = NULL;
lmerge_matched:;
slot = saved_slot;
/*
* UPDATE/DELETE is only invoked for matched rows. And we must have found
* the tupleid of the target row in that case. We fetch using SnapshotAny
* because we might get called again after EvalPlanQual returns us a new
* tuple. This tuple may not be visible to our MVCC snapshot.
*/
Assert(tupleid != NULL);
tuple.t_self = *tupleid;
if (!heap_fetch(resultRelInfo->ri_RelationDesc, SnapshotAny, &tuple,
&buffer, true, NULL))
elog(ERROR, "Failed to fetch the target tuple");
/* Store target's existing tuple in the state's dedicated slot */
ExecStoreTuple(&tuple, mtstate->mt_existing, buffer, false);
foreach(l, mergeMatchedActionStates)
{
MergeActionState *action = (MergeActionState *) lfirst(l);
/*
* Test condition, if any
*
* In the absence of a condition we perform the action unconditionally
* (no need to check separately since ExecQual() will return true if
* there are no conditions to evaluate).
*/
if (!ExecQual(action->whenqual, econtext))
continue;
/*
* Check if the existing target tuple meet the USING checks of
* UPDATE/DELETE RLS policies. If those checks fail, we throw an
* error.
*
* The WITH CHECK quals are applied in ExecUpdate() and hence we need
* not do anything special to handle them.
*
* NOTE: We must do this after WHEN quals are evaluated so that we
* check policies only when they matter.
*/
if (resultRelInfo->ri_WithCheckOptions)
{
ExecWithCheckOptions(action->commandType == CMD_UPDATE ?
WCO_RLS_MERGE_UPDATE_CHECK : WCO_RLS_MERGE_DELETE_CHECK,
resultRelInfo,
mtstate->mt_existing,
mtstate->ps.state);
}
/* Perform stated action */
switch (action->commandType)
{
case CMD_UPDATE:
/*
* We set up the projection earlier, so all we do here is
* Project, no need for any other tasks prior to the
* ExecUpdate.
*/
if (mtstate->mt_partition_tuple_routing)
ExecSetSlotDescriptor(mtstate->mt_mergeproj, action->tupDesc);
ExecProject(action->proj);
/*
* We don't call ExecFilterJunk() because the projected tuple
* using the UPDATE action's targetlist doesn't have a junk
* attribute.
*/
slot = ExecUpdate(mtstate, tupleid, NULL,
mtstate->mt_mergeproj,
slot, epqstate, estate,
&tuple_updated, &hufd,
action, mtstate->canSetTag);
break;
case CMD_DELETE:
/* Nothing to Project for a DELETE action */
slot = ExecDelete(mtstate, tupleid, NULL,
slot, epqstate, estate,
&tuple_deleted, false, &hufd, action,
mtstate->canSetTag);
break;
default:
elog(ERROR, "unknown action in MERGE WHEN MATCHED clause");
}
/*
* Check for any concurrent update/delete operation which may have
* prevented our update/delete. We also check for situations where we
* might be trying to update/delete the same tuple twice.
*/
if ((action->commandType == CMD_UPDATE && !tuple_updated) ||
(action->commandType == CMD_DELETE && !tuple_deleted))
{
switch (hufd.result)
{
case HeapTupleMayBeUpdated:
break;
case HeapTupleInvisible:
/*
* This state should never be reached since the underlying
* JOIN runs with a MVCC snapshot and should only return
* rows visible to us.
*/
elog(ERROR, "unexpected invisible tuple");
break;
case HeapTupleSelfUpdated:
/*
* SQLStandard disallows this for MERGE.
*/
if (TransactionIdIsCurrentTransactionId(hufd.xmax))
ereport(ERROR,
(errcode(ERRCODE_CARDINALITY_VIOLATION),
errmsg("MERGE command cannot affect row a second time"),
errhint("Ensure that not more than one source row matches any one target row")));
/* This shouldn't happen */
elog(ERROR, "attempted to update or delete invisible tuple");
break;
case HeapTupleUpdated:
/*
* The target tuple was concurrently updated/deleted by
* some other transaction.
*
* If the current tuple is that last tuple in the update
* chain, then we know that the tuple was concurrently
* deleted. Just return and let the caller try NOT MATCHED
* actions.
*
* If the current tuple was concurrently updated, then we
* must run the EvalPlanQual() with the new version of the
* tuple. If EvalPlanQual() does not return a tuple then
* we switch to the NOT MATCHED list of actions.
* If it does return a tuple and the join qual is
* still satisfied, then we just need to recheck the
* MATCHED actions, starting from the top, and execute the
* first qualifying action.
*/
if (!ItemPointerEquals(tupleid, &hufd.ctid))
{
TupleTableSlot *epqslot;
/*
* Since we generate a JOIN query with a target table
* RTE different than the result relation RTE, we must
* pass in the RTI of the relation used in the join
* query and not the one from result relation.
*/
Assert(resultRelInfo->ri_mergeTargetRTI > 0);
epqslot = EvalPlanQual(estate,
epqstate,
resultRelInfo->ri_RelationDesc,
GetEPQRangeTableIndex(resultRelInfo),
LockTupleExclusive,
&hufd.ctid,
hufd.xmax);
if (!TupIsNull(epqslot))
{
(void) ExecGetJunkAttribute(epqslot,
resultRelInfo->ri_junkFilter->jf_junkAttNo,
&isNull);
/*
* A non-NULL ctid means that we are still dealing
* with MATCHED case. But we must retry from the
* start with the updated tuple to ensure that the
* first qualifying WHEN MATCHED action is
* executed.
*
* We don't use the new slot returned by
* EvalPlanQual because we anyways re-install the
* new target tuple in econtext->ecxt_scantuple
* before re-evaluating WHEN AND conditions and
* re-projecting the update targetlists. The
* source side tuple does not change and hence we
* can safely continue to use the old slot.
*/
if (!isNull)
{
/*
* Must update *tupleid to the TID of the
* newer tuple found in the update chain.
*/
*tupleid = hufd.ctid;
ReleaseBuffer(buffer);
goto lmerge_matched;
}
}
}
/*
* Tell the caller about the updated TID, restore the
* state back and return.
*/
*tupleid = hufd.ctid;
estate->es_result_relation_info = saved_resultRelInfo;
ReleaseBuffer(buffer);
return false;
default:
break;
}
}
if (action->commandType == CMD_UPDATE && tuple_updated)
InstrCountFiltered2(&mtstate->ps, 1);
if (action->commandType == CMD_DELETE && tuple_deleted)
InstrCountFiltered3(&mtstate->ps, 1);
/*
* We've activated one of the WHEN clauses, so we don't search
* further. This is required behaviour, not an optimization.
*/
estate->es_result_relation_info = saved_resultRelInfo;
break;
}
ReleaseBuffer(buffer);
/*
* Successfully executed an action or no qualifying action was found.
*/
return true;
}
/*
* Execute the first qualifying NOT MATCHED action.
*/
static void
ExecMergeNotMatched(ModifyTableState *mtstate, EState *estate,
TupleTableSlot *slot)
{
PartitionTupleRouting *proute = mtstate->mt_partition_tuple_routing;
ExprContext *econtext = mtstate->ps.ps_ExprContext;
List *mergeNotMatchedActionStates = NIL;
ResultRelInfo *resultRelInfo;
ListCell *l;
TupleTableSlot *myslot;
/*
* We are dealing with NOT MATCHED tuple. Since for MERGE, partition tree
* is not expanded for the result relation, we continue to work with the
* currently active result relation, which should be of the root of the
* partition tree.
*/
resultRelInfo = mtstate->resultRelInfo;
/*
* For INSERT actions, root relation's merge action is OK since the
* INSERT's targetlist and the WHEN conditions can only refer to the
* source relation and hence it does not matter which result relation we
* work with.
*/
mergeNotMatchedActionStates =
resultRelInfo->ri_mergeState->notMatchedActionStates;
/*
* Make source tuple available to ExecQual and ExecProject. We don't need
* the target tuple since the WHEN quals and the targetlist can't refer to
* the target columns.
*/
econtext->ecxt_scantuple = NULL;
econtext->ecxt_innertuple = slot;
econtext->ecxt_outertuple = NULL;
foreach(l, mergeNotMatchedActionStates)
{
MergeActionState *action = (MergeActionState *) lfirst(l);
/*
* Test condition, if any
*
* In the absence of a condition we perform the action unconditionally
* (no need to check separately since ExecQual() will return true if
* there are no conditions to evaluate).
*/
if (!ExecQual(action->whenqual, econtext))
continue;
/* Perform stated action */
switch (action->commandType)
{
case CMD_INSERT:
/*
* We set up the projection earlier, so all we do here is
* Project, no need for any other tasks prior to the
* ExecInsert.
*/
if (mtstate->mt_partition_tuple_routing)
ExecSetSlotDescriptor(mtstate->mt_mergeproj, action->tupDesc);
ExecProject(action->proj);
/*
* ExecPrepareTupleRouting may modify the passed-in slot. Hence
* pass a local reference so that action->slot is not modified.
*/
myslot = mtstate->mt_mergeproj;
/* Prepare for tuple routing if needed. */
if (proute)
myslot = ExecPrepareTupleRouting(mtstate, estate, proute,
resultRelInfo, myslot);
slot = ExecInsert(mtstate, myslot, slot,
estate, action,
mtstate->canSetTag);
/* Revert ExecPrepareTupleRouting's state change. */
if (proute)
estate->es_result_relation_info = resultRelInfo;
InstrCountFiltered1(&mtstate->ps, 1);
break;
case CMD_NOTHING:
/* Do Nothing */
break;
default:
elog(ERROR, "unknown action in MERGE WHEN NOT MATCHED clause");
}
break;
}
}
/*
* Perform MERGE.
*/
void
ExecMerge(ModifyTableState *mtstate, EState *estate, TupleTableSlot *slot,
JunkFilter *junkfilter, ResultRelInfo *resultRelInfo)
{
ExprContext *econtext = mtstate->ps.ps_ExprContext;
ItemPointer tupleid;
ItemPointerData tuple_ctid;
bool matched = false;
char relkind;
Datum datum;
bool isNull;
relkind = resultRelInfo->ri_RelationDesc->rd_rel->relkind;
Assert(relkind == RELKIND_RELATION ||
relkind == RELKIND_PARTITIONED_TABLE);
/*
* Reset per-tuple memory context to free any expression evaluation
* storage allocated in the previous cycle.
*/
ResetExprContext(econtext);
/*
* We run a JOIN between the target relation and the source relation to
* find a set of candidate source rows that has matching row in the target
* table and a set of candidate source rows that does not have matching
* row in the target table. If the join returns us a tuple with target
* relation's tid set, that implies that the join found a matching row for
* the given source tuple. This case triggers the WHEN MATCHED clause of
* the MERGE. Whereas a NULL in the target relation's ctid column
* indicates a NOT MATCHED case.
*/
datum = ExecGetJunkAttribute(slot, junkfilter->jf_junkAttNo, &isNull);
if (!isNull)
{
matched = true;
tupleid = (ItemPointer) DatumGetPointer(datum);
tuple_ctid = *tupleid; /* be sure we don't free ctid!! */
tupleid = &tuple_ctid;
}
else
{
matched = false;
tupleid = NULL; /* we don't need it for INSERT actions */
}
/*
* If we are dealing with a WHEN MATCHED case, we execute the first action
* for which the additional WHEN MATCHED AND quals pass. If an action
* without quals is found, that action is executed.
*
* Similarly, if we are dealing with WHEN NOT MATCHED case, we look at the
* given WHEN NOT MATCHED actions in sequence until one passes.
*
* Things get interesting in case of concurrent update/delete of the
* target tuple. Such concurrent update/delete is detected while we are
* executing a WHEN MATCHED action.
*
* A concurrent update can:
*
* 1. modify the target tuple so that it no longer satisfies the
* additional quals attached to the current WHEN MATCHED action OR
*
* In this case, we are still dealing with a WHEN MATCHED case, but
* we should recheck the list of WHEN MATCHED actions and choose the first
* one that satisfies the new target tuple.
*
* 2. modify the target tuple so that the join quals no longer pass and
* hence the source tuple no longer has a match.
*
* In the second case, the source tuple no longer matches the target tuple,
* so we now instead find a qualifying WHEN NOT MATCHED action to execute.
*
* A concurrent delete, changes a WHEN MATCHED case to WHEN NOT MATCHED.
*
* ExecMergeMatched takes care of following the update chain and
* re-finding the qualifying WHEN MATCHED action, as long as the updated
* target tuple still satisfies the join quals i.e. it still remains a
* WHEN MATCHED case. If the tuple gets deleted or the join quals fail, it
* returns and we try ExecMergeNotMatched. Given that ExecMergeMatched
* always make progress by following the update chain and we never switch
* from ExecMergeNotMatched to ExecMergeMatched, there is no risk of a
* livelock.
*/
if (matched)
matched = ExecMergeMatched(mtstate, estate, slot, junkfilter, tupleid);
/*
* Either we were dealing with a NOT MATCHED tuple or ExecMergeNotMatched()
* returned "false", indicating the previously MATCHED tuple is no longer a
* matching tuple.
*/
if (!matched)
ExecMergeNotMatched(mtstate, estate, slot);
}

660
src/backend/parser/parse_merge.c
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@ -0,0 +1,660 @@
/*-------------------------------------------------------------------------
*
* parse_merge.c
* handle merge-statement in parser
*
* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/parser/parse_merge.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "miscadmin.h"
#include "access/sysattr.h"
#include "nodes/makefuncs.h"
#include "parser/analyze.h"
#include "parser/parse_collate.h"
#include "parser/parsetree.h"
#include "parser/parser.h"
#include "parser/parse_clause.h"
#include "parser/parse_merge.h"
#include "parser/parse_relation.h"
#include "parser/parse_target.h"
#include "utils/rel.h"
#include "utils/relcache.h"
static int transformMergeJoinClause(ParseState *pstate, Node *merge,
List **mergeSourceTargetList);
static void setNamespaceForMergeAction(ParseState *pstate,
MergeAction *action);
static void setNamespaceVisibilityForRTE(List *namespace, RangeTblEntry *rte,
bool rel_visible,
bool cols_visible);
static List *expandSourceTL(ParseState *pstate, RangeTblEntry *rte,
int rtindex);
/*
* Special handling for MERGE statement is required because we assemble
* the query manually. This is similar to setTargetTable() followed
* by transformFromClause() but with a few less steps.
*
* Process the FROM clause and add items to the query's range table,
* joinlist, and namespace.
*
* A special targetlist comprising of the columns from the right-subtree of
* the join is populated and returned. Note that when the JoinExpr is
* setup by transformMergeStmt, the left subtree has the target result
* relation and the right subtree has the source relation.
*
* Returns the rangetable index of the target relation.
*/
static int
transformMergeJoinClause(ParseState *pstate, Node *merge,
List **mergeSourceTargetList)
{
RangeTblEntry *rte,
*rt_rte;
List *namespace;
int rtindex,
rt_rtindex;
Node *n;
int mergeTarget_relation = list_length(pstate->p_rtable) + 1;
Var *var;
TargetEntry *te;
n = transformFromClauseItem(pstate, merge,
&rte,
&rtindex,
&rt_rte,
&rt_rtindex,
&namespace);
pstate->p_joinlist = list_make1(n);
/*
* We created an internal join between the target and the source relation
* to carry out the MERGE actions. Normally such an unaliased join hides
* the joining relations, unless the column references are qualified.
* Also, any unqualified column references are resolved to the Join RTE, if
* there is a matching entry in the targetlist. But the way MERGE
* execution is later setup, we expect all column references to resolve to
* either the source or the target relation. Hence we must not add the
* Join RTE to the namespace.
*
* The last entry must be for the top-level Join RTE. We don't want to
* resolve any references to the Join RTE. So discard that.
*
* We also do not want to resolve any references from the leftside of the
* Join since that corresponds to the target relation. References to the
* columns of the target relation must be resolved from the result
* relation and not the one that is used in the join. So the
* mergeTarget_relation is marked invisible to both qualified as well as
* unqualified references.
*/
Assert(list_length(namespace) > 1);
namespace = list_truncate(namespace, list_length(namespace) - 1);
pstate->p_namespace = list_concat(pstate->p_namespace, namespace);
setNamespaceVisibilityForRTE(pstate->p_namespace,
rt_fetch(mergeTarget_relation, pstate->p_rtable), false, false);
/*
* Expand the right relation and add its columns to the
* mergeSourceTargetList. Note that the right relation can either be a
* plain relation or a subquery or anything that can have a
* RangeTableEntry.
*/
*mergeSourceTargetList = expandSourceTL(pstate, rt_rte, rt_rtindex);
/*
* Add a whole-row-Var entry to support references to "source.*".
*/
var = makeWholeRowVar(rt_rte, rt_rtindex, 0, false);
te = makeTargetEntry((Expr *) var, list_length(*mergeSourceTargetList) + 1,
NULL, true);
*mergeSourceTargetList = lappend(*mergeSourceTargetList, te);
return mergeTarget_relation;
}
/*
* Make appropriate changes to the namespace visibility while transforming
* individual action's quals and targetlist expressions. In particular, for
* INSERT actions we must only see the source relation (since INSERT action is
* invoked for NOT MATCHED tuples and hence there is no target tuple to deal
* with). On the other hand, UPDATE and DELETE actions can see both source and
* target relations.
*
* Also, since the internal Join node can hide the source and target
* relations, we must explicitly make the respective relation as visible so
* that columns can be referenced unqualified from these relations.
*/
static void
setNamespaceForMergeAction(ParseState *pstate, MergeAction *action)
{
RangeTblEntry *targetRelRTE,
*sourceRelRTE;
/* Assume target relation is at index 1 */
targetRelRTE = rt_fetch(1, pstate->p_rtable);
/*
* Assume that the top-level join RTE is at the end. The source relation
* is just before that.
*/
sourceRelRTE = rt_fetch(list_length(pstate->p_rtable) - 1, pstate->p_rtable);
switch (action->commandType)
{
case CMD_INSERT:
/*
* Inserts can't see target relation, but they can see source
* relation.
*/
setNamespaceVisibilityForRTE(pstate->p_namespace,
targetRelRTE, false, false);
setNamespaceVisibilityForRTE(pstate->p_namespace,
sourceRelRTE, true, true);
break;
case CMD_UPDATE:
case CMD_DELETE:
/*
* Updates and deletes can see both target and source relations.
*/
setNamespaceVisibilityForRTE(pstate->p_namespace,
targetRelRTE, true, true);
setNamespaceVisibilityForRTE(pstate->p_namespace,
sourceRelRTE, true, true);
break;
case CMD_NOTHING:
break;
default:
elog(ERROR, "unknown action in MERGE WHEN clause");
}
}
/*
* transformMergeStmt -
* transforms a MERGE statement
*/
Query *
transformMergeStmt(ParseState *pstate, MergeStmt *stmt)
{
Query *qry = makeNode(Query);
ListCell *l;
AclMode targetPerms = ACL_NO_RIGHTS;
bool is_terminal[2];
JoinExpr *joinexpr;
RangeTblEntry *resultRelRTE, *mergeRelRTE;
/* There can't be any outer WITH to worry about */
Assert(pstate->p_ctenamespace == NIL);
qry->commandType = CMD_MERGE;
/*
* Check WHEN clauses for permissions and sanity
*/
is_terminal[0] = false;
is_terminal[1] = false;
foreach(l, stmt->mergeActionList)
{
MergeAction *action = (MergeAction *) lfirst(l);
int when_type = (action->matched ? 0 : 1);
/*
* Collect action types so we can check Target permissions
*/
switch (action->commandType)
{
case CMD_INSERT:
{
InsertStmt *istmt = (InsertStmt *) action->stmt;
SelectStmt *selectStmt = (SelectStmt *) istmt->selectStmt;
/*
* The grammar allows attaching ORDER BY, LIMIT, FOR
* UPDATE, or WITH to a VALUES clause and also multiple
* VALUES clauses. If we have any of those, ERROR.
*/
if (selectStmt && (selectStmt->valuesLists == NIL ||
selectStmt->sortClause != NIL ||
selectStmt->limitOffset != NULL ||
selectStmt->limitCount != NULL ||
selectStmt->lockingClause != NIL ||
selectStmt->withClause != NULL))
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("SELECT not allowed in MERGE INSERT statement")));
if (selectStmt && list_length(selectStmt->valuesLists) > 1)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("Multiple VALUES clauses not allowed in MERGE INSERT statement")));
targetPerms |= ACL_INSERT;
}
break;
case CMD_UPDATE:
targetPerms |= ACL_UPDATE;
break;
case CMD_DELETE:
targetPerms |= ACL_DELETE;
break;
case CMD_NOTHING:
break;
default:
elog(ERROR, "unknown action in MERGE WHEN clause");
}
/*
* Check for unreachable WHEN clauses
*/
if (action->condition == NULL)
is_terminal[when_type] = true;
else if (is_terminal[when_type])
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("unreachable WHEN clause specified after unconditional WHEN clause")));
}
/*
* Construct a query of the form
* SELECT relation.ctid --junk attribute
* ,relation.tableoid --junk attribute
* ,source_relation.<somecols>
* ,relation.<somecols>
* FROM relation RIGHT JOIN source_relation
* ON join_condition; -- no WHERE clause - all conditions are applied in
* executor
*
* stmt->relation is the target relation, given as a RangeVar
* stmt->source_relation is a RangeVar or subquery
*
* We specify the join as a RIGHT JOIN as a simple way of forcing the
* first (larg) RTE to refer to the target table.
*
* The MERGE query's join can be tuned in some cases, see below for these
* special case tweaks.
*
* We set QSRC_PARSER to show query constructed in parse analysis
*
* Note that we have only one Query for a MERGE statement and the planner
* is called only once. That query is executed once to produce our stream
* of candidate change rows, so the query must contain all of the columns
* required by each of the targetlist or conditions for each action.
*
* As top-level statements INSERT, UPDATE and DELETE have a Query, whereas
* with MERGE the individual actions do not require separate planning,
* only different handling in the executor. See nodeModifyTable handling
* of commandType CMD_MERGE.
*
* A sub-query can include the Target, but otherwise the sub-query cannot
* reference the outermost Target table at all.
*/
qry->querySource = QSRC_PARSER;
/*
* Setup the target table. Unlike regular UPDATE/DELETE, we don't expand
* inheritance for the target relation in case of MERGE.
*
* This special arrangement is required for handling partitioned tables
* because we perform an JOIN between the target and the source relation to
* identify the matching and not-matching rows. If we take the usual path
* of expanding the target table's inheritance and create one subplan per
* partition, then we we won't be able to correctly identify the matching
* and not-matching rows since for a given source row, there may not be a
* matching row in one partition, but it may exists in some other
* partition. So we must first append all the qualifying rows from all the
* partitions and then do the matching.
*
* Once a target row is returned by the underlying join, we find the
* correct partition and setup required state to carry out UPDATE/DELETE.
* All of this happens during execution.
*/
qry->resultRelation = setTargetTable(pstate, stmt->relation,
false, /* do not expand inheritance */
true, targetPerms);
/*
* Create a JOIN between the target and the source relation.
*/
joinexpr = makeNode(JoinExpr);
joinexpr->isNatural = false;
joinexpr->alias = NULL;
joinexpr->usingClause = NIL;
joinexpr->quals = stmt->join_condition;
joinexpr->larg = (Node *) stmt->relation;
joinexpr->rarg = (Node *) stmt->source_relation;
/*
* Simplify the MERGE query as much as possible
*
* These seem like things that could go into Optimizer, but they are
* semantic simplifications rather than optimizations, per se.
*
* If there are no INSERT actions we won't be using the non-matching
* candidate rows for anything, so no need for an outer join. We do still
* need an inner join for UPDATE and DELETE actions.
*/
if (targetPerms & ACL_INSERT)
joinexpr->jointype = JOIN_RIGHT;
else
joinexpr->jointype = JOIN_INNER;
/*
* We use a special purpose transformation here because the normal
* routines don't quite work right for the MERGE case.
*
* A special mergeSourceTargetList is setup by transformMergeJoinClause().
* It refers to all the attributes provided by the source relation. This
* is later used by set_plan_refs() to fix the UPDATE/INSERT target lists
* to so that they can correctly fetch the attributes from the source
* relation.
*
* The target relation when used in the underlying join, gets a new RTE
* with rte->inh set to true. We remember this RTE (and later pass on to
* the planner and executor) for two main reasons:
*
* 1. If we ever need to run EvalPlanQual while performing MERGE, we must
* make the modified tuple available to the underlying join query, which is
* using a different RTE from the resultRelation RTE.
*
* 2. rewriteTargetListMerge() requires the RTE of the underlying join in
* order to add junk CTID and TABLEOID attributes.
*/
qry->mergeTarget_relation = transformMergeJoinClause(pstate, (Node *) joinexpr,
&qry->mergeSourceTargetList);
/*
* The target table referenced in the MERGE is looked up twice; once while
* setting it up as the result relation and again when it's used in the
* underlying the join query. In some rare situations, it may happen that
* these lookups return different results, for example, if a new relation
* with the same name gets created in a schema which is ahead in the
* search_path, in between the two lookups.
*
* It's a very narrow case, but nevertheless we guard against it by simply
* checking if the OIDs returned by the two lookups is the same. If not, we
* just throw an error.
*/
Assert(qry->resultRelation > 0);
Assert(qry->mergeTarget_relation > 0);
/* Fetch both the RTEs */
resultRelRTE = rt_fetch(qry->resultRelation, pstate->p_rtable);
mergeRelRTE = rt_fetch(qry->mergeTarget_relation, pstate->p_rtable);
if (resultRelRTE->relid != mergeRelRTE->relid)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("relation referenced by MERGE statement has changed")));
/*
* This query should just provide the source relation columns. Later, in
* preprocess_targetlist(), we shall also add "ctid" attribute of the
* target relation to ensure that the target tuple can be fetched
* correctly.
*/
qry->targetList = qry->mergeSourceTargetList;
/* qry has no WHERE clause so absent quals are shown as NULL */
qry->jointree = makeFromExpr(pstate->p_joinlist, NULL);
qry->rtable = pstate->p_rtable;
/*
* XXX MERGE is unsupported in various cases
*/
if (!(pstate->p_target_relation->rd_rel->relkind == RELKIND_RELATION ||
pstate->p_target_relation->rd_rel->relkind == RELKIND_PARTITIONED_TABLE))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("MERGE is not supported for this relation type")));
if (pstate->p_target_relation->rd_rel->relkind != RELKIND_PARTITIONED_TABLE &&
pstate->p_target_relation->rd_rel->relhassubclass)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("MERGE is not supported for relations with inheritance")));
if (pstate->p_target_relation->rd_rel->relhasrules)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("MERGE is not supported for relations with rules")));
/*
* We now have a good query shape, so now look at the when conditions and
* action targetlists.
*
* Overall, the MERGE Query's targetlist is NIL.
*
* Each individual action has its own targetlist that needs separate
* transformation. These transforms don't do anything to the overall
* targetlist, since that is only used for resjunk columns.
*
* We can reference any column in Target or Source, which is OK because
* both of those already have RTEs. There is nothing like the EXCLUDED
* pseudo-relation for INSERT ON CONFLICT.
*/
foreach(l, stmt->mergeActionList)
{
MergeAction *action = (MergeAction *) lfirst(l);
/*
* Set namespace for the specific action. This must be done before
* analyzing the WHEN quals and the action targetlisst.
*/
setNamespaceForMergeAction(pstate, action);
/*
* Transform the when condition.
*
* Note that these quals are NOT added to the join quals; instead they
* are evaluated separately during execution to decide which of the
* WHEN MATCHED or WHEN NOT MATCHED actions to execute.
*/
action->qual = transformWhereClause(pstate, action->condition,
EXPR_KIND_MERGE_WHEN_AND, "WHEN");
/*
* Transform target lists for each INSERT and UPDATE action stmt
*/
switch (action->commandType)
{
case CMD_INSERT:
{
InsertStmt *istmt = (InsertStmt *) action->stmt;
SelectStmt *selectStmt = (SelectStmt *) istmt->selectStmt;
List *exprList = NIL;
ListCell *lc;
RangeTblEntry *rte;
ListCell *icols;
ListCell *attnos;
List *icolumns;
List *attrnos;
pstate->p_is_insert = true;
icolumns = checkInsertTargets(pstate, istmt->cols, &attrnos);
Assert(list_length(icolumns) == list_length(attrnos));
/*
* Handle INSERT much like in transformInsertStmt
*/
if (selectStmt == NULL)
{
/*
* We have INSERT ... DEFAULT VALUES. We can handle
* this case by emitting an empty targetlist --- all
* columns will be defaulted when the planner expands
* the targetlist.
*/
exprList = NIL;
}
else
{
/*
* Process INSERT ... VALUES with a single VALUES
* sublist. We treat this case separately for
* efficiency. The sublist is just computed directly
* as the Query's targetlist, with no VALUES RTE. So
* it works just like a SELECT without any FROM.
*/
List *valuesLists = selectStmt->valuesLists;
Assert(list_length(valuesLists) == 1);
Assert(selectStmt->intoClause == NULL);
/*
* Do basic expression transformation (same as a ROW()
* expr, but allow SetToDefault at top level)
*/
exprList = transformExpressionList(pstate,
(List *) linitial(valuesLists),
EXPR_KIND_VALUES_SINGLE,
true);
/* Prepare row for assignment to target table */
exprList = transformInsertRow(pstate, exprList,
istmt->cols,
icolumns, attrnos,
false);
}
/*
* Generate action's target list using the computed list
* of expressions. Also, mark all the target columns as
* needing insert permissions.
*/
rte = pstate->p_target_rangetblentry;
icols = list_head(icolumns);
attnos = list_head(attrnos);
foreach(lc, exprList)
{
Expr *expr = (Expr *) lfirst(lc);
ResTarget *col;
AttrNumber attr_num;
TargetEntry *tle;
col = lfirst_node(ResTarget, icols);
attr_num = (AttrNumber) lfirst_int(attnos);
tle = makeTargetEntry(expr,
attr_num,
col->name,
false);
action->targetList = lappend(action->targetList, tle);
rte->insertedCols = bms_add_member(rte->insertedCols,
attr_num - FirstLowInvalidHeapAttributeNumber);
icols = lnext(icols);
attnos = lnext(attnos);
}
}
break;
case CMD_UPDATE:
{
UpdateStmt *ustmt = (UpdateStmt *) action->stmt;
pstate->p_is_insert = false;
action->targetList = transformUpdateTargetList(pstate, ustmt->targetList);
}
break;
case CMD_DELETE:
break;
case CMD_NOTHING:
action->targetList = NIL;
break;
default:
elog(ERROR, "unknown action in MERGE WHEN clause");
}
}
qry->mergeActionList = stmt->mergeActionList;
/* XXX maybe later */
qry->returningList = NULL;
qry->hasTargetSRFs = false;
qry->hasSubLinks = pstate->p_hasSubLinks;
assign_query_collations(pstate, qry);
return qry;
}
static void
setNamespaceVisibilityForRTE(List *namespace, RangeTblEntry *rte,
bool rel_visible,
bool cols_visible)
{
ListCell *lc;
foreach(lc, namespace)
{
ParseNamespaceItem *nsitem = (ParseNamespaceItem *) lfirst(lc);
if (nsitem->p_rte == rte)
{
nsitem->p_rel_visible = rel_visible;
nsitem->p_cols_visible = cols_visible;
break;
}
}
}
/*
* Expand the source relation to include all attributes of this RTE.
*
* This function is very similar to expandRelAttrs except that we don't mark
* columns for SELECT privileges. That will be decided later when we transform
* the action targetlists and the WHEN quals for actual references to the
* source relation.
*/
static List *
expandSourceTL(ParseState *pstate, RangeTblEntry *rte, int rtindex)
{
List *names,
*vars;
ListCell *name,
*var;
List *te_list = NIL;
expandRTE(rte, rtindex, 0, -1, false, &names, &vars);
/*
* Require read access to the table.
*/
rte->requiredPerms |= ACL_SELECT;
forboth(name, names, var, vars)
{
char *label = strVal(lfirst(name));
Var *varnode = (Var *) lfirst(var);
TargetEntry *te;
te = makeTargetEntry((Expr *) varnode,
(AttrNumber) pstate->p_next_resno++,
label,
false);
te_list = lappend(te_list, te);
}
Assert(name == NULL && var == NULL); /* lists not the same length? */
return te_list;
}

22
src/include/executor/nodeMerge.h
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/*-------------------------------------------------------------------------
*
* nodeMerge.h
*
*
* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/executor/nodeMerge.h
*
*-------------------------------------------------------------------------
*/
#ifndef NODEMERGE_H
#define NODEMERGE_H
#include "nodes/execnodes.h"
extern void
ExecMerge(ModifyTableState *mtstate, EState *estate, TupleTableSlot *slot,
JunkFilter *junkfilter, ResultRelInfo *resultRelInfo);
#endif /* NODEMERGE_H */

19
src/include/parser/parse_merge.h
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/*-------------------------------------------------------------------------
*
* parse_merge.h
* handle merge-stmt in parser
*
*
* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/parser/parse_merge.h
*
*-------------------------------------------------------------------------
*/
#ifndef PARSE_MERGE_H
#define PARSE_MERGE_H
#include "parser/parse_node.h"
extern Query *transformMergeStmt(ParseState *pstate, MergeStmt *stmt);
#endif

97
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Parsed test spec with 2 sessions
starting permutation: delete c1 select2 c2
step delete: DELETE FROM target t WHERE t.key = 1;
step c1: COMMIT;
step select2: SELECT * FROM target;
key val
step c2: COMMIT;
starting permutation: merge_delete c1 select2 c2
step merge_delete: MERGE INTO target t USING (SELECT 1 as key) s ON s.key = t.key WHEN MATCHED THEN DELETE;
step c1: COMMIT;
step select2: SELECT * FROM target;
key val
step c2: COMMIT;
starting permutation: delete c1 update1 select2 c2
step delete: DELETE FROM target t WHERE t.key = 1;
step c1: COMMIT;
step update1: UPDATE target t SET val = t.val || ' updated by update1' WHERE t.key = 1;
step select2: SELECT * FROM target;
key val
step c2: COMMIT;
starting permutation: merge_delete c1 update1 select2 c2
step merge_delete: MERGE INTO target t USING (SELECT 1 as key) s ON s.key = t.key WHEN MATCHED THEN DELETE;
step c1: COMMIT;
step update1: UPDATE target t SET val = t.val || ' updated by update1' WHERE t.key = 1;
step select2: SELECT * FROM target;
key val
step c2: COMMIT;
starting permutation: delete c1 merge2 select2 c2
step delete: DELETE FROM target t WHERE t.key = 1;
step c1: COMMIT;
step merge2: MERGE INTO target t USING (SELECT 1 as key, 'merge2a' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
step select2: SELECT * FROM target;
key val
1 merge2a
step c2: COMMIT;
starting permutation: merge_delete c1 merge2 select2 c2
step merge_delete: MERGE INTO target t USING (SELECT 1 as key) s ON s.key = t.key WHEN MATCHED THEN DELETE;
step c1: COMMIT;
step merge2: MERGE INTO target t USING (SELECT 1 as key, 'merge2a' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
step select2: SELECT * FROM target;
key val
1 merge2a
step c2: COMMIT;
starting permutation: delete update1 c1 select2 c2
step delete: DELETE FROM target t WHERE t.key = 1;
step update1: UPDATE target t SET val = t.val || ' updated by update1' WHERE t.key = 1; <waiting ...>
step c1: COMMIT;
step update1: <... completed>
step select2: SELECT * FROM target;
key val
step c2: COMMIT;
starting permutation: merge_delete update1 c1 select2 c2
step merge_delete: MERGE INTO target t USING (SELECT 1 as key) s ON s.key = t.key WHEN MATCHED THEN DELETE;
step update1: UPDATE target t SET val = t.val || ' updated by update1' WHERE t.key = 1; <waiting ...>
step c1: COMMIT;
step update1: <... completed>
step select2: SELECT * FROM target;
key val
step c2: COMMIT;
starting permutation: delete merge2 c1 select2 c2
step delete: DELETE FROM target t WHERE t.key = 1;
step merge2: MERGE INTO target t USING (SELECT 1 as key, 'merge2a' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val; <waiting ...>
step c1: COMMIT;
step merge2: <... completed>
step select2: SELECT * FROM target;
key val
1 merge2a
step c2: COMMIT;
starting permutation: merge_delete merge2 c1 select2 c2
step merge_delete: MERGE INTO target t USING (SELECT 1 as key) s ON s.key = t.key WHEN MATCHED THEN DELETE;
step merge2: MERGE INTO target t USING (SELECT 1 as key, 'merge2a' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val; <waiting ...>
step c1: COMMIT;
step merge2: <... completed>
step select2: SELECT * FROM target;
key val
1 merge2a
step c2: COMMIT;

84
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Parsed test spec with 2 sessions
starting permutation: merge1 c1 select2 c2
step merge1: MERGE INTO target t USING (SELECT 1 as key, 'merge1' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge1';
step c1: COMMIT;
step select2: SELECT * FROM target;
key val
1 merge1
step c2: COMMIT;
starting permutation: merge1 c1 merge2 select2 c2
step merge1: MERGE INTO target t USING (SELECT 1 as key, 'merge1' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge1';
step c1: COMMIT;
step merge2: MERGE INTO target t USING (SELECT 1 as key, 'merge2' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge2';
step select2: SELECT * FROM target;
key val
1 merge1 updated by merge2
step c2: COMMIT;
starting permutation: insert1 merge2 c1 select2 c2
step insert1: INSERT INTO target VALUES (1, 'insert1');
step merge2: MERGE INTO target t USING (SELECT 1 as key, 'merge2' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge2'; <waiting ...>
step c1: COMMIT;
step merge2: <... completed>
error in steps c1 merge2: ERROR: duplicate key value violates unique constraint "target_pkey"
step select2: SELECT * FROM target;
ERROR: current transaction is aborted, commands ignored until end of transaction block
step c2: COMMIT;
starting permutation: merge1 merge2 c1 select2 c2
step merge1: MERGE INTO target t USING (SELECT 1 as key, 'merge1' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge1';
step merge2: MERGE INTO target t USING (SELECT 1 as key, 'merge2' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge2'; <waiting ...>
step c1: COMMIT;
step merge2: <... completed>
error in steps c1 merge2: ERROR: duplicate key value violates unique constraint "target_pkey"
step select2: SELECT * FROM target;
ERROR: current transaction is aborted, commands ignored until end of transaction block
step c2: COMMIT;
starting permutation: merge1 merge2 a1 select2 c2
step merge1: MERGE INTO target t USING (SELECT 1 as key, 'merge1' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge1';
step merge2: MERGE INTO target t USING (SELECT 1 as key, 'merge2' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge2'; <waiting ...>
step a1: ABORT;
step merge2: <... completed>
step select2: SELECT * FROM target;
key val
1 merge2
step c2: COMMIT;
starting permutation: delete1 insert1 c1 merge2 select2 c2
step delete1: DELETE FROM target WHERE key = 1;
step insert1: INSERT INTO target VALUES (1, 'insert1');
step c1: COMMIT;
step merge2: MERGE INTO target t USING (SELECT 1 as key, 'merge2' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge2';
step select2: SELECT * FROM target;
key val
1 insert1 updated by merge2
step c2: COMMIT;
starting permutation: delete1 insert1 merge2 c1 select2 c2
step delete1: DELETE FROM target WHERE key = 1;
step insert1: INSERT INTO target VALUES (1, 'insert1');
step merge2: MERGE INTO target t USING (SELECT 1 as key, 'merge2' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge2'; <waiting ...>
step c1: COMMIT;
step merge2: <... completed>
error in steps c1 merge2: ERROR: duplicate key value violates unique constraint "target_pkey"
step select2: SELECT * FROM target;
ERROR: current transaction is aborted, commands ignored until end of transaction block
step c2: COMMIT;
starting permutation: delete1 insert1 merge2i c1 select2 c2
step delete1: DELETE FROM target WHERE key = 1;
step insert1: INSERT INTO target VALUES (1, 'insert1');
step merge2i: MERGE INTO target t USING (SELECT 1 as key, 'merge2' as val) s ON s.key = t.key WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge2';
step c1: COMMIT;
step select2: SELECT * FROM target;
key val
1 insert1
step c2: COMMIT;

106
src/test/isolation/expected/merge-match-recheck.out
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Parsed test spec with 2 sessions
starting permutation: update1 merge_status c2 select1 c1
step update1: UPDATE target t SET balance = balance + 10, val = t.val || ' updated by update1' WHERE t.key = 1;
step merge_status:
MERGE INTO target t
USING (SELECT 1 as key) s
ON s.key = t.key
WHEN MATCHED AND status = 's1' THEN
UPDATE SET status = 's2', val = t.val || ' when1'
WHEN MATCHED AND status = 's2' THEN
UPDATE SET status = 's3', val = t.val || ' when2'
WHEN MATCHED AND status = 's3' THEN
UPDATE SET status = 's4', val = t.val || ' when3';
<waiting ...>
step c2: COMMIT;
step merge_status: <... completed>
step select1: SELECT * FROM target;
key balance status val
1 170 s2 setup updated by update1 when1
step c1: COMMIT;
starting permutation: update2 merge_status c2 select1 c1
step update2: UPDATE target t SET status = 's2', val = t.val || ' updated by update2' WHERE t.key = 1;
step merge_status:
MERGE INTO target t
USING (SELECT 1 as key) s
ON s.key = t.key
WHEN MATCHED AND status = 's1' THEN
UPDATE SET status = 's2', val = t.val || ' when1'
WHEN MATCHED AND status = 's2' THEN
UPDATE SET status = 's3', val = t.val || ' when2'
WHEN MATCHED AND status = 's3' THEN
UPDATE SET status = 's4', val = t.val || ' when3';
<waiting ...>
step c2: COMMIT;
step merge_status: <... completed>
step select1: SELECT * FROM target;
key balance status val
1 160 s3 setup updated by update2 when2
step c1: COMMIT;
starting permutation: update3 merge_status c2 select1 c1
step update3: UPDATE target t SET status = 's3', val = t.val || ' updated by update3' WHERE t.key = 1;
step merge_status:
MERGE INTO target t
USING (SELECT 1 as key) s
ON s.key = t.key
WHEN MATCHED AND status = 's1' THEN
UPDATE SET status = 's2', val = t.val || ' when1'
WHEN MATCHED AND status = 's2' THEN
UPDATE SET status = 's3', val = t.val || ' when2'
WHEN MATCHED AND status = 's3' THEN
UPDATE SET status = 's4', val = t.val || ' when3';
<waiting ...>
step c2: COMMIT;
step merge_status: <... completed>
step select1: SELECT * FROM target;
key balance status val
1 160 s4 setup updated by update3 when3
step c1: COMMIT;
starting permutation: update5 merge_status c2 select1 c1
step update5: UPDATE target t SET status = 's5', val = t.val || ' updated by update5' WHERE t.key = 1;
step merge_status:
MERGE INTO target t
USING (SELECT 1 as key) s
ON s.key = t.key
WHEN MATCHED AND status = 's1' THEN
UPDATE SET status = 's2', val = t.val || ' when1'
WHEN MATCHED AND status = 's2' THEN
UPDATE SET status = 's3', val = t.val || ' when2'
WHEN MATCHED AND status = 's3' THEN
UPDATE SET status = 's4', val = t.val || ' when3';
<waiting ...>
step c2: COMMIT;
step merge_status: <... completed>
step select1: SELECT * FROM target;
key balance status val
1 160 s5 setup updated by update5
step c1: COMMIT;
starting permutation: update_bal1 merge_bal c2 select1 c1
step update_bal1: UPDATE target t SET balance = 50, val = t.val || ' updated by update_bal1' WHERE t.key = 1;
step merge_bal:
MERGE INTO target t
USING (SELECT 1 as key) s
ON s.key = t.key
WHEN MATCHED AND balance < 100 THEN
UPDATE SET balance = balance * 2, val = t.val || ' when1'
WHEN MATCHED AND balance < 200 THEN
UPDATE SET balance = balance * 4, val = t.val || ' when2'
WHEN MATCHED AND balance < 300 THEN
UPDATE SET balance = balance * 8, val = t.val || ' when3';
<waiting ...>
step c2: COMMIT;
step merge_bal: <... completed>
step select1: SELECT * FROM target;
key balance status val
1 100 s1 setup updated by update_bal1 when1
step c1: COMMIT;

213
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Parsed test spec with 2 sessions
starting permutation: merge1 c1 select2 c2
step merge1:
MERGE INTO target t
USING (SELECT 1 as key, 'merge1' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
step c1: COMMIT;
step select2: SELECT * FROM target;
key val
2 setup1 updated by merge1
step c2: COMMIT;
starting permutation: merge1 c1 merge2a select2 c2
step merge1:
MERGE INTO target t
USING (SELECT 1 as key, 'merge1' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
step c1: COMMIT;
step merge2a:
MERGE INTO target t
USING (SELECT 1 as key, 'merge2a' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
step select2: SELECT * FROM target;
key val
2 setup1 updated by merge1
1 merge2a
step c2: COMMIT;
starting permutation: merge1 merge2a c1 select2 c2
step merge1:
MERGE INTO target t
USING (SELECT 1 as key, 'merge1' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
step merge2a:
MERGE INTO target t
USING (SELECT 1 as key, 'merge2a' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
<waiting ...>
step c1: COMMIT;
step merge2a: <... completed>
step select2: SELECT * FROM target;
key val
2 setup1 updated by merge1
1 merge2a
step c2: COMMIT;
starting permutation: merge1 merge2a a1 select2 c2
step merge1:
MERGE INTO target t
USING (SELECT 1 as key, 'merge1' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
step merge2a:
MERGE INTO target t
USING (SELECT 1 as key, 'merge2a' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
<waiting ...>
step a1: ABORT;
step merge2a: <... completed>
step select2: SELECT * FROM target;
key val
2 setup1 updated by merge2a
step c2: COMMIT;
starting permutation: merge1 merge2b c1 select2 c2
step merge1:
MERGE INTO target t
USING (SELECT 1 as key, 'merge1' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
step merge2b:
MERGE INTO target t
USING (SELECT 1 as key, 'merge2b' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED AND t.key < 2 THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
<waiting ...>
step c1: COMMIT;
step merge2b: <... completed>
step select2: SELECT * FROM target;
key val
2 setup1 updated by merge1
1 merge2b
step c2: COMMIT;
starting permutation: merge1 merge2c c1 select2 c2
step merge1:
MERGE INTO target t
USING (SELECT 1 as key, 'merge1' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
step merge2c:
MERGE INTO target t
USING (SELECT 1 as key, 'merge2c' as val) s
ON s.key = t.key AND t.key < 2
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
<waiting ...>
step c1: COMMIT;
step merge2c: <... completed>
step select2: SELECT * FROM target;
key val
2 setup1 updated by merge1
1 merge2c
step c2: COMMIT;
starting permutation: pa_merge1 pa_merge2a c1 pa_select2 c2
step pa_merge1:
MERGE INTO pa_target t
USING (SELECT 1 as key, 'pa_merge1' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set val = t.val || ' updated by ' || s.val;
step pa_merge2a:
MERGE INTO pa_target t
USING (SELECT 1 as key, 'pa_merge2a' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
<waiting ...>
step c1: COMMIT;
step pa_merge2a: <... completed>
step pa_select2: SELECT * FROM pa_target;
key val
2 initial
2 initial updated by pa_merge2a
step c2: COMMIT;
starting permutation: pa_merge2 pa_merge2a c1 pa_select2 c2
step pa_merge2:
MERGE INTO pa_target t
USING (SELECT 1 as key, 'pa_merge1' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
step pa_merge2a:
MERGE INTO pa_target t
USING (SELECT 1 as key, 'pa_merge2a' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
<waiting ...>
step c1: COMMIT;
step pa_merge2a: <... completed>
step pa_select2: SELECT * FROM pa_target;
key val
1 pa_merge2a
2 initial
2 initial updated by pa_merge1
step c2: COMMIT;

51
src/test/isolation/specs/merge-delete.spec
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# MERGE DELETE
#
# This test looks at the interactions involving concurrent deletes
# comparing the behavior of MERGE, DELETE and UPDATE
setup
{
CREATE TABLE target (key int primary key, val text);
INSERT INTO target VALUES (1, 'setup1');
}
teardown
{
DROP TABLE target;
}
session "s1"
setup
{
BEGIN ISOLATION LEVEL READ COMMITTED;
}
step "delete" { DELETE FROM target t WHERE t.key = 1; }
step "merge_delete" { MERGE INTO target t USING (SELECT 1 as key) s ON s.key = t.key WHEN MATCHED THEN DELETE; }
step "c1" { COMMIT; }
step "a1" { ABORT; }
session "s2"
setup
{
BEGIN ISOLATION LEVEL READ COMMITTED;
}
step "update1" { UPDATE target t SET val = t.val || ' updated by update1' WHERE t.key = 1; }
step "merge2" { MERGE INTO target t USING (SELECT 1 as key, 'merge2a' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val; }
step "select2" { SELECT * FROM target; }
step "c2" { COMMIT; }
# Basic effects
permutation "delete" "c1" "select2" "c2"
permutation "merge_delete" "c1" "select2" "c2"
# One after the other, no concurrency
permutation "delete" "c1" "update1" "select2" "c2"
permutation "merge_delete" "c1" "update1" "select2" "c2"
permutation "delete" "c1" "merge2" "select2" "c2"
permutation "merge_delete" "c1" "merge2" "select2" "c2"
# Now with concurrency
permutation "delete" "update1" "c1" "select2" "c2"
permutation "merge_delete" "update1" "c1" "select2" "c2"
permutation "delete" "merge2" "c1" "select2" "c2"
permutation "merge_delete" "merge2" "c1" "select2" "c2"

52
src/test/isolation/specs/merge-insert-update.spec
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# MERGE INSERT UPDATE
#
# This looks at how we handle concurrent INSERTs, illustrating how the
# behavior differs from INSERT ... ON CONFLICT
setup
{
CREATE TABLE target (key int primary key, val text);
}
teardown
{
DROP TABLE target;
}
session "s1"
setup
{
BEGIN ISOLATION LEVEL READ COMMITTED;
}
step "merge1" { MERGE INTO target t USING (SELECT 1 as key, 'merge1' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge1'; }
step "delete1" { DELETE FROM target WHERE key = 1; }
step "insert1" { INSERT INTO target VALUES (1, 'insert1'); }
step "c1" { COMMIT; }
step "a1" { ABORT; }
session "s2"
setup
{
BEGIN ISOLATION LEVEL READ COMMITTED;
}
step "merge2" { MERGE INTO target t USING (SELECT 1 as key, 'merge2' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge2'; }
step "merge2i" { MERGE INTO target t USING (SELECT 1 as key, 'merge2' as val) s ON s.key = t.key WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge2'; }
step "select2" { SELECT * FROM target; }
step "c2" { COMMIT; }
step "a2" { ABORT; }
# Basic effects
permutation "merge1" "c1" "select2" "c2"
permutation "merge1" "c1" "merge2" "select2" "c2"
# check concurrent inserts
permutation "insert1" "merge2" "c1" "select2" "c2"
permutation "merge1" "merge2" "c1" "select2" "c2"
permutation "merge1" "merge2" "a1" "select2" "c2"
# check how we handle when visible row has been concurrently deleted, then same key re-inserted
permutation "delete1" "insert1" "c1" "merge2" "select2" "c2"
permutation "delete1" "insert1" "merge2" "c1" "select2" "c2"
permutation "delete1" "insert1" "merge2i" "c1" "select2" "c2"

79
src/test/isolation/specs/merge-match-recheck.spec
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# MERGE MATCHED RECHECK
#
# This test looks at what happens when we have complex
# WHEN MATCHED AND conditions and a concurrent UPDATE causes a
# recheck of the AND condition on the new row
setup
{
CREATE TABLE target (key int primary key, balance integer, status text, val text);
INSERT INTO target VALUES (1, 160, 's1', 'setup');
}
teardown
{
DROP TABLE target;
}
session "s1"
setup
{
BEGIN ISOLATION LEVEL READ COMMITTED;
}
step "merge_status"
{
MERGE INTO target t
USING (SELECT 1 as key) s
ON s.key = t.key
WHEN MATCHED AND status = 's1' THEN
UPDATE SET status = 's2', val = t.val || ' when1'
WHEN MATCHED AND status = 's2' THEN
UPDATE SET status = 's3', val = t.val || ' when2'
WHEN MATCHED AND status = 's3' THEN
UPDATE SET status = 's4', val = t.val || ' when3';
}
step "merge_bal"
{
MERGE INTO target t
USING (SELECT 1 as key) s
ON s.key = t.key
WHEN MATCHED AND balance < 100 THEN
UPDATE SET balance = balance * 2, val = t.val || ' when1'
WHEN MATCHED AND balance < 200 THEN
UPDATE SET balance = balance * 4, val = t.val || ' when2'
WHEN MATCHED AND balance < 300 THEN
UPDATE SET balance = balance * 8, val = t.val || ' when3';
}
step "select1" { SELECT * FROM target; }
step "c1" { COMMIT; }
step "a1" { ABORT; }
session "s2"
setup
{
BEGIN ISOLATION LEVEL READ COMMITTED;
}
step "update1" { UPDATE target t SET balance = balance + 10, val = t.val || ' updated by update1' WHERE t.key = 1; }
step "update2" { UPDATE target t SET status = 's2', val = t.val || ' updated by update2' WHERE t.key = 1; }
step "update3" { UPDATE target t SET status = 's3', val = t.val || ' updated by update3' WHERE t.key = 1; }
step "update5" { UPDATE target t SET status = 's5', val = t.val || ' updated by update5' WHERE t.key = 1; }
step "update_bal1" { UPDATE target t SET balance = 50, val = t.val || ' updated by update_bal1' WHERE t.key = 1; }
step "select2" { SELECT * FROM target; }
step "c2" { COMMIT; }
# merge_status sees concurrently updated row and rechecks WHEN conditions, but recheck passes and final status = 's2'
permutation "update1" "merge_status" "c2" "select1" "c1"
# merge_status sees concurrently updated row and rechecks WHEN conditions, recheck fails, so final status = 's3' not 's2'
permutation "update2" "merge_status" "c2" "select1" "c1"
# merge_status sees concurrently updated row and rechecks WHEN conditions, recheck fails, so final status = 's4' not 's2'
permutation "update3" "merge_status" "c2" "select1" "c1"
# merge_status sees concurrently updated row and rechecks WHEN conditions, recheck fails, but we skip update and MERGE does nothing
permutation "update5" "merge_status" "c2" "select1" "c1"
# merge_bal sees concurrently updated row and rechecks WHEN conditions, recheck fails, so final balance = 100 not 640
permutation "update_bal1" "merge_bal" "c2" "select1" "c1"

132
src/test/isolation/specs/merge-update.spec
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# MERGE UPDATE
#
# This test exercises atypical cases
# 1. UPDATEs of PKs that change the join in the ON clause
# 2. UPDATEs with WHEN AND conditions that would fail after concurrent update
# 3. UPDATEs with extra ON conditions that would fail after concurrent update
setup
{
CREATE TABLE target (key int primary key, val text);
INSERT INTO target VALUES (1, 'setup1');
CREATE TABLE pa_target (key integer, val text)
PARTITION BY LIST (key);
CREATE TABLE part1 (key integer, val text);
CREATE TABLE part2 (val text, key integer);
CREATE TABLE part3 (key integer, val text);
ALTER TABLE pa_target ATTACH PARTITION part1 FOR VALUES IN (1,4);
ALTER TABLE pa_target ATTACH PARTITION part2 FOR VALUES IN (2,5,6);
ALTER TABLE pa_target ATTACH PARTITION part3 DEFAULT;
INSERT INTO pa_target VALUES (1, 'initial');
INSERT INTO pa_target VALUES (2, 'initial');
}
teardown
{
DROP TABLE target;
DROP TABLE pa_target CASCADE;
}
session "s1"
setup
{
BEGIN ISOLATION LEVEL READ COMMITTED;
}
step "merge1"
{
MERGE INTO target t
USING (SELECT 1 as key, 'merge1' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
}
step "pa_merge1"
{
MERGE INTO pa_target t
USING (SELECT 1 as key, 'pa_merge1' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set val = t.val || ' updated by ' || s.val;
}
step "pa_merge2"
{
MERGE INTO pa_target t
USING (SELECT 1 as key, 'pa_merge1' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
}
step "c1" { COMMIT; }
step "a1" { ABORT; }
session "s2"
setup
{
BEGIN ISOLATION LEVEL READ COMMITTED;
}
step "merge2a"
{
MERGE INTO target t
USING (SELECT 1 as key, 'merge2a' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
}
step "merge2b"
{
MERGE INTO target t
USING (SELECT 1 as key, 'merge2b' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED AND t.key < 2 THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
}
step "merge2c"
{
MERGE INTO target t
USING (SELECT 1 as key, 'merge2c' as val) s
ON s.key = t.key AND t.key < 2
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
}
step "pa_merge2a"
{
MERGE INTO pa_target t
USING (SELECT 1 as key, 'pa_merge2a' as val) s
ON s.key = t.key
WHEN NOT MATCHED THEN
INSERT VALUES (s.key, s.val)
WHEN MATCHED THEN
UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val;
}
step "select2" { SELECT * FROM target; }
step "pa_select2" { SELECT * FROM pa_target; }
step "c2" { COMMIT; }
# Basic effects
permutation "merge1" "c1" "select2" "c2"
# One after the other, no concurrency
permutation "merge1" "c1" "merge2a" "select2" "c2"
# Now with concurrency
permutation "merge1" "merge2a" "c1" "select2" "c2"
permutation "merge1" "merge2a" "a1" "select2" "c2"
permutation "merge1" "merge2b" "c1" "select2" "c2"
permutation "merge1" "merge2c" "c1" "select2" "c2"
permutation "pa_merge1" "pa_merge2a" "c1" "pa_select2" "c2"
permutation "pa_merge2" "pa_merge2a" "c1" "pa_select2" "c2"

1673
src/test/regress/expected/merge.out
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1173
src/test/regress/sql/merge.sql
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