This implements asynchronous execution, which runs multiple parts of a
non-parallel-aware Append concurrently rather than serially to improve
performance when possible. Currently, the only node type that can be
run concurrently is a ForeignScan that is an immediate child of such an
Append. In the case where such ForeignScans access data on different
remote servers, this would run those ForeignScans concurrently, and
overlap the remote operations to be performed simultaneously, so it'll
improve the performance especially when the operations involve
time-consuming ones such as remote join and remote aggregation.
We may extend this to other node types such as joins or aggregates over
ForeignScans in the future.
This also adds the support for postgres_fdw, which is enabled by the
table-level/server-level option "async_capable". The default is false.
Robert Haas, Kyotaro Horiguchi, Thomas Munro, and myself. This commit
is mostly based on the patch proposed by Robert Haas, but also uses
stuff from the patch proposed by Kyotaro Horiguchi and from the patch
proposed by Thomas Munro. Reviewed by Kyotaro Horiguchi, Konstantin
Knizhnik, Andrey Lepikhov, Movead Li, Thomas Munro, Justin Pryzby, and
others.
Discussion: https://postgr.es/m/CA%2BTgmoaXQEt4tZ03FtQhnzeDEMzBck%2BLrni0UWHVVgOTnA6C1w%40mail.gmail.com
Discussion: https://postgr.es/m/CA%2BhUKGLBRyu0rHrDCMC4%3DRn3252gogyp1SjOgG8SEKKZv%3DFwfQ%40mail.gmail.com
Discussion: https://postgr.es/m/20200228.170650.667613673625155850.horikyota.ntt%40gmail.com
Here we add a new output parameter to estimate_num_groups() to allow it to
inform the caller of additional, possibly useful information about the
estimation.
The new output parameter is a struct that currently contains just a single
field with a set of flags. This was done rather than having the flags as
an output parameter to allow future fields to be added without having to
change the signature of the function at a later date when we want to pass
back further information that might not be suitable to store in the flags
field.
It seems reasonable that one day in the future that the planner would want
to know more about the estimation. For example, how many individual sets
of statistics was the estimation generated from? The planner may want to
take that into account if we ever want to consider risks as well as costs
when generating plans.
For now, there's only 1 flag we set in the flags field. This is to
indicate if the estimation fell back on using the hard-coded constants in
any part of the estimation. Callers may like to change their behavior if
this is set, and this gives them the ability to do so. Callers may pass
the flag pointer as NULL if they have no interest in obtaining any
additional information about the estimate.
We're not adding any actual usages of these flags here. Some follow-up
commits will make use of this feature. Additionally, we're also not
making any changes to add support for clauselist_selectivity() and
clauselist_selectivity_ext(). However, if this is required in the future
then the same struct being added here should be fine to use as a new
output argument for those functions too.
Author: David Rowley
Discussion: https://postgr.es/m/CAApHDvqQqpk=1W-G_ds7A9CsXX3BggWj_7okinzkLVhDubQzjA@mail.gmail.com
A cross-partition update on a partitioned table is implemented as a
delete followed by an insert. With foreign partitions, this was however
causing issues, because the FDW and core may disagree on when to enable
batching. postgres_fdw was only allowing batching for plain inserts
(CMD_INSERT) while core was trying to batch the insert component of the
cross-partition update. Fix by restricting core to apply batching only
to plain CMD_INSERT queries.
It's possible to allow batching for cross-partition updates, but that
will require more extensive changes, so better to leave that for a
separate patch.
Author: Amit Langote
Reviewed-by: Tomas Vondra, Takayuki Tsunakawa
Discussion: https://postgr.es/m/20200628151002.7x5laxwpgvkyiu3q@development
If a cross-partition UPDATE violates a constraint on the target partition,
and the columns in the new partition are in different physical order than
in the parent, the error message can reveal columns that the user does not
have SELECT permission on. A similar bug was fixed earlier in commit
804b6b6db4.
The cause of the bug is that the callers of the
ExecBuildSlotValueDescription() function got confused when constructing
the list of modified columns. If the tuple was routed from a parent, we
converted the tuple to the parent's format, but the list of modified
columns was grabbed directly from the child's RTE entry.
ExecUpdateLockMode() had a similar issue. That lead to confusion on which
columns are key columns, leading to wrong tuple lock being taken on tables
referenced by foreign keys, when a row is updated with INSERT ON CONFLICT
UPDATE. A new isolation test is added for that corner case.
With this patch, the ri_RangeTableIndex field is no longer set for
partitions that don't have an entry in the range table. Previously, it was
set to the RTE entry of the parent relation, but that was confusing.
NOTE: This modifies the ResultRelInfo struct, replacing the
ri_PartitionRoot field with ri_RootResultRelInfo. That's a bit risky to
backpatch, because it breaks any extensions accessing the field. The
change that ri_RangeTableIndex is not set for partitions could potentially
break extensions, too. The ResultRelInfos are visible to FDWs at least,
and this patch required small changes to postgres_fdw. Nevertheless, this
seem like the least bad option. I don't think these fields widely used in
extensions; I don't think there are FDWs out there that uses the FDW
"direct update" API, other than postgres_fdw. If there is, you will get a
compilation error, so hopefully it is caught quickly.
Backpatch to 11, where support for both cross-partition UPDATEs, and unique
indexes on partitioned tables, were added.
Reviewed-by: Amit Langote
Security: CVE-2021-3393
Commit 08d2d58a2 added an assertion assuming that the retrieved_rows
estimate for a foreign relation, which is re-used to cost pre-sorted
foreign paths with local stats, is set to at least one row in
estimate_path_cost_size(), which isn't correct because if the relation
is a foreign table with tuples=0, the estimate would be set to 0 there
when not using remote estimates.
Per bug #16807 from Alexander Lakhin. Back-patch to v13 where the
aforementioned commit went in.
Author: Etsuro Fujita
Reviewed-by: Kyotaro Horiguchi
Discussion: https://postgr.es/m/16807-9fe4e08fbaa5c7ce%40postgresql.org
Previously, pull_varnos() took the relids of a PlaceHolderVar as being
equal to the relids in its contents, but that fails to account for the
possibility that we have to postpone evaluation of the PHV due to outer
joins. This could result in a malformed plan. The known cases end up
triggering the "failed to assign all NestLoopParams to plan nodes"
sanity check in createplan.c, but other symptoms may be possible.
The right value to use is the join level we actually intend to evaluate
the PHV at. We can get that from the ph_eval_at field of the associated
PlaceHolderInfo. However, there are some places that call pull_varnos()
before the PlaceHolderInfos have been created; in that case, fall back
to the conservative assumption that the PHV will be evaluated at its
syntactic level. (In principle this might result in missing some legal
optimization, but I'm not aware of any cases where it's an issue in
practice.) Things are also a bit ticklish for calls occurring during
deconstruct_jointree(), but AFAICS the ph_eval_at fields should have
reached their final values by the time we need them.
The main problem in making this work is that pull_varnos() has no
way to get at the PlaceHolderInfos. We can fix that easily, if a
bit tediously, in HEAD by passing it the planner "root" pointer.
In the back branches that'd cause an unacceptable API/ABI break for
extensions, so leave the existing entry points alone and add new ones
with the additional parameter. (If an old entry point is called and
encounters a PHV, it'll fall back to using the syntactic level,
again possibly missing some valid optimization.)
Back-patch to v12. The computation is surely also wrong before that,
but it appears that we cannot reach a bad plan thanks to join order
restrictions imposed on the subquery that the PlaceHolderVar came from.
The error only became reachable when commit 4be058fe9 allowed trivial
subqueries to be collapsed out completely, eliminating their join order
restrictions.
Per report from Stephan Springl.
Discussion: https://postgr.es/m/171041.1610849523@sss.pgh.pa.us
Extends the FDW API to allow batching inserts into foreign tables. That
is usually much more efficient than inserting individual rows, due to
high latency for each round-trip to the foreign server.
It was possible to implement something similar in the regular FDW API,
but it was inconvenient and there were issues with reporting the number
of actually inserted rows etc. This extends the FDW API with two new
functions:
* GetForeignModifyBatchSize - allows the FDW picking optimal batch size
* ExecForeignBatchInsert - inserts a batch of rows at once
Currently, only INSERT queries support batching. Support for DELETE and
UPDATE may be added in the future.
This also implements batching for postgres_fdw. The batch size may be
specified using "batch_size" option both at the server and table level.
The initial patch version was written by me, but it was rewritten and
improved in many ways by Takayuki Tsunakawa.
Author: Takayuki Tsunakawa
Reviewed-by: Tomas Vondra, Amit Langote
Discussion: https://postgr.es/m/20200628151002.7x5laxwpgvkyiu3q@development
A number of places were using appendStringInfo() when they could have been
using appendStringInfoString() instead. While there's no functionality
change there, it's just more efficient to use appendStringInfoString()
when no formatting is required. Likewise for some
appendStringInfoString() calls which were just appending a single char.
We can just use appendStringInfoChar() for that.
Additionally, many places were using appendPQExpBuffer() when they could
have used appendPQExpBufferStr(). Change those too.
Patch by Zhijie Hou, but further searching by me found significantly more
places that deserved the same treatment.
Author: Zhijie Hou, David Rowley
Discussion: https://postgr.es/m/cb172cf4361e4c7ba7167429070979d4@G08CNEXMBPEKD05.g08.fujitsu.local
FDWs that can perform an UPDATE/DELETE remotely using the "direct modify"
set of APIs need to access the ResultRelInfo of the target table. That's
currently available in EState.es_result_relation_info, but the next
commit will remove that field.
This commit adds a new resultRelation field in ForeignScan, to store the
target relation's RT index, and the corresponding ResultRelInfo in
ForeignScanState. The FDW's PlanDirectModify callback is expected to set
'resultRelation' along with 'operation'. The core code doesn't need them
for anything, they are for the convenience of FDW's Begin- and
IterateDirectModify callbacks.
Authors: Amit Langote, Etsuro Fujita
Discussion: https://www.postgresql.org/message-id/CA%2BHiwqGEmiib8FLiHMhKB%2BCH5dRgHSLc5N5wnvc4kym%2BZYpQEQ%40mail.gmail.com
Historically, we've considered the state with relpages and reltuples
both zero as indicating that we do not know the table's tuple density.
This is problematic because it's impossible to distinguish "never yet
vacuumed" from "vacuumed and seen to be empty". In particular, a user
cannot use VACUUM or ANALYZE to override the planner's normal heuristic
that an empty table should not be believed to be empty because it is
probably about to get populated. That heuristic is a good safety
measure, so I don't care to abandon it, but there should be a way to
override it if the table is indeed intended to stay empty.
Hence, represent the initial state of ignorance by setting reltuples
to -1 (relpages is still set to zero), and apply the minimum-ten-pages
heuristic only when reltuples is still -1. If the table is empty,
VACUUM or ANALYZE (but not CREATE INDEX) will override that to
reltuples = relpages = 0, and then we'll plan on that basis.
This requires a bunch of fiddly little changes, but we can get rid of
some ugly kluges that were formerly needed to maintain the old definition.
One notable point is that FDWs' GetForeignRelSize methods will see
baserel->tuples = -1 when no ANALYZE has been done on the foreign table.
That seems like a net improvement, since those methods were formerly
also in the dark about what baserel->tuples = 0 really meant. Still,
it is an API change.
I bumped catversion because code predating this change would get confused
by seeing reltuples = -1.
Discussion: https://postgr.es/m/F02298E0-6EF4-49A1-BCB6-C484794D9ACC@thebuild.com
Commit d2d8a229bc introduced Incremental Sort, but it was considered
only in create_ordered_paths() as an alternative to regular Sort. There
are many other places that require sorted input and might benefit from
considering Incremental Sort too.
This patch modifies a number of those places, but not all. The concern
is that just adding Incremental Sort to any place that already adds
Sort may increase the number of paths considered, negatively affecting
planning time, without any benefit. So we've taken a more conservative
approach, based on analysis of which places do affect a set of queries
that did seem practical. This means some less common queries may not
benefit from Incremental Sort yet.
Author: Tomas Vondra
Reviewed-by: James Coleman
Discussion: https://postgr.es/m/CAPpHfds1waRZ=NOmueYq0sx1ZSCnt+5QJvizT8ndT2=etZEeAQ@mail.gmail.com
EXPLAIN generally only adds schema qualifications to table names when
VERBOSE is specified. In postgres_fdw's "Relations" output, table
names were always so qualified, but that was an implementation
restriction: in the original coding, we didn't have access to the
verbose flag at the time the string was generated. After the code
rearrangement of commit 4526951d5, we do have that info available
at the right time, so make this output follow the normal rule.
Discussion: https://postgr.es/m/12424.1575168015@sss.pgh.pa.us
The relation aliases shown in the "Relations" line for a foreign scan
didn't always agree with those used in the rest of EXPLAIN's output.
The regression test result changes appearing here provide examples.
It's really impossible for postgres_fdw to duplicate EXPLAIN's alias
assignment logic during postgresGetForeignRelSize(), because of the
de-duplication that EXPLAIN does on a global basis --- and anyway,
trying to duplicate that would be unmaintainable. Instead, just put
numeric rangetable indexes into the string, and convert those to
table names/aliases in postgresExplainForeignScan, which does have
access to the results of ruleutils.c's alias assignment logic.
Aside from being more reliable, this shifts some work from planning
to EXPLAIN, which is a good tradeoff for performance. (I also
changed from using StringInfo to using psprintf, which makes the
code slightly simpler and reduces its memory consumption.)
A kluge required by this solution is that we have to reverse-engineer
the rtoffset applied by setrefs.c. If that logic ever fails
(presumably because the member tables of a join got offset by
different amounts), we'll need some more cooperation with setrefs.c
to keep things straight. But for now, there's no need for that.
Arguably this is a back-patchable bug fix, but since this is a mostly
cosmetic issue and there have been no field complaints, I'll refrain
for now.
Discussion: https://postgr.es/m/12424.1575168015@sss.pgh.pa.us
This gives an alternative way of catching exceptions, for the common
case where the cleanup code is the same in the error and non-error
cases. So instead of
PG_TRY();
{
... code that might throw ereport(ERROR) ...
}
PG_CATCH();
{
cleanup();
PG_RE_THROW();
}
PG_END_TRY();
cleanup();
one can write
PG_TRY();
{
... code that might throw ereport(ERROR) ...
}
PG_FINALLY();
{
cleanup();
}
PG_END_TRY();
Discussion: https://www.postgresql.org/message-id/flat/95a822c3-728b-af0e-d7e5-71890507ae0c%402ndquadrant.com
The basic rule we follow here is to always first include 'postgres.h' or
'postgres_fe.h' whichever is applicable, then system header includes and
then Postgres header includes. In this, we also follow that all the
Postgres header includes are in order based on their ASCII value. We
generally follow these rules, but the code has deviated in many places.
This commit makes it consistent just for contrib modules. The later
commits will enforce similar rules in other parts of code.
Author: Vignesh C
Reviewed-by: Amit Kapila
Discussion: https://postgr.es/m/CALDaNm2Sznv8RR6Ex-iJO6xAdsxgWhCoETkaYX=+9DW3q0QCfA@mail.gmail.com
In the wake of commit 1cff1b95a, the result of list_concat no longer
shares the ListCells of the second input. Therefore, we can replace
"list_concat(x, list_copy(y))" with just "list_concat(x, y)".
To improve call sites that were list_copy'ing the first argument,
or both arguments, invent "list_concat_copy()" which produces a new
list sharing no ListCells with either input. (This is a bit faster
than "list_concat(list_copy(x), y)" because it makes the result list
the right size to start with.)
In call sites that were not list_copy'ing the second argument, the new
semantics mean that we are usually leaking the second List's storage,
since typically there is no remaining pointer to it. We considered
inventing another list_copy variant that would list_free the second
input, but concluded that for most call sites it isn't worth worrying
about, given the relative compactness of the new List representation.
(Note that in cases where such leakage would happen, the old code
already leaked the second List's header; so we're only discussing
the size of the leak not whether there is one. I did adjust two or
three places that had been troubling to free that header so that
they manually free the whole second List.)
Patch by me; thanks to David Rowley for review.
Discussion: https://postgr.es/m/11587.1550975080@sss.pgh.pa.us
Previously, in the loop in postgresAcquireSampleRowsFunc() to iterate
fetching rows from a given remote table, we redundantly 1) determined the
fetch size by parsing the table's server/table-level options and then 2)
constructed the fetch command; remove that redundancy.
Author: Etsuro Fujita
Reviewed-by: Julien Rouhaud
Discussion: https://postgr.es/m/CAPmGK17_urk9qkLV65_iYMFw64z5qhdfhY=tMVV6Jg4KNYx8+w@mail.gmail.com
Commit aa09cd242 modified estimate_path_cost_size() so that it reuses
cached costs of a basic foreign path for a given foreign-base/join
relation when costing pre-sorted foreign paths for that relation, but it
incorrectly re-computed retrieved_rows, an estimated number of rows
fetched from the remote side, which is needed for costing both the basic
and pre-sorted foreign paths. To fix, handle retrieved_rows the same way
as the cached costs: store in that relation's fpinfo the retrieved_rows
estimate computed for costing the basic foreign path, and reuse it when
costing the pre-sorted foreign paths. Also, reuse the rows/width
estimates stored in that relation's fpinfo when costing the pre-sorted
foreign paths, to make the code consistent.
In commit ffab494a4, to extend the costing mentioned above to the
foreign-grouping case, I made a change to add_foreign_grouping_paths() to
store in a given foreign-grouped relation's RelOptInfo the rows estimate
for that relation for reuse, but this patch makes that change unnecessary
since we already store the row estimate in that relation's fpinfo, which
this patch reuses when costing a foreign path for that relation with the
sortClause ordering; remove that change.
In passing, fix thinko in commit 7012b132d: in estimate_path_cost_size(),
the width estimate for a given foreign-grouped relation to be stored in
that relation's fpinfo was reset incorrectly when costing a basic foreign
path for that relation with local stats.
Apply the patch to HEAD only to avoid destabilizing existing plan choices.
Author: Etsuro Fujita
Discussion: https://postgr.es/m/CAPmGK17jaJLPDEkgnP2VmkOg=5wT8YQ1CqssU8JRpZ_NSE+dqQ@mail.gmail.com
Previously, in postgresPlanForeignModify, we planned an UPDATE operation
on a foreign table so that we transmit only columns that were explicitly
targets of the UPDATE, so as to avoid unnecessary data transmission, but
if there were BEFORE ROW UPDATE triggers on the foreign table, those
triggers might change values for non-target columns, in which case we
would miss sending changed values for those columns. Prevent optimizing
away transmitting all columns if there are BEFORE ROW UPDATE triggers on
the foreign table.
This is an oversight in commit 7cbe57c34 which added triggers on foreign
tables, so apply the patch all the way back to 9.4 where that came in.
Author: Shohei Mochizuki
Reviewed-by: Amit Langote
Discussion: https://postgr.es/m/201905270152.x4R1q3qi014550@toshiba.co.jp
This is still using the 2.0 version of pg_bsd_indent.
I thought it would be good to commit this separately,
so as to document the differences between 2.0 and 2.1 behavior.
Discussion: https://postgr.es/m/16296.1558103386@sss.pgh.pa.us
In commit 7012b132d0, which added support for aggregate pushdown in
postgres_fdw, the expense of evaluating the final scan/join target
computed by make_group_input_target() was not accounted for at all in
costing aggregate pushdown paths with local statistics. The right fix
for this would be to have a separate upper stage to adjust the final
scan/join relation (see comments for apply_scanjoin_target_to_paths());
but for now, fix by adding the tlist eval cost when costing aggregate
pushdown paths with local statistics.
Apply this to HEAD only to avoid destabilizing existing plan choices.
Author: Etsuro Fujita
Reviewed-By: Antonin Houska
Discussion: https://postgr.es/m/5C66A056.60007%40lab.ntt.co.jp
foreign_grouping_ok() is willing to put fairly arbitrary expressions into
the targetlist of a remote SELECT that's doing grouping or aggregation on
the remote side, including expressions that have no foreign component to
them at all. This is possibly a bit dubious from an efficiency standpoint;
but it rises to the level of a crash-causing bug if the expression is just
a Param or non-foreign Var. In that case, the expression will necessarily
also appear in the fdw_exprs list of values we need to send to the remote
server, and then setrefs.c's set_foreignscan_references will mistakenly
replace the fdw_exprs entry with a Var referencing the targetlist result.
The root cause of this problem is bad design in commit e7cb7ee14: it put
logic into set_foreignscan_references that IMV is postgres_fdw-specific,
and yet this bug shows that it isn't postgres_fdw-specific enough. The
transformation being done on fdw_exprs assumes that fdw_exprs is to be
evaluated with the fdw_scan_tlist as input, which is not how postgres_fdw
uses it; yet it could be the right thing for some other FDW. (In the
bigger picture, setrefs.c has no business assuming this for the other
expression fields of a ForeignScan either.)
The right fix therefore would be to expand the FDW API so that the
FDW could inform setrefs.c how it intends to evaluate these various
expressions. We can't change that in the back branches though, and we
also can't just summarily change setrefs.c's behavior there, or we're
likely to break external FDWs.
As a stopgap, therefore, hack up postgres_fdw so that it won't attempt
to send targetlist entries that look exactly like the fdw_exprs entries
they'd produce. In most cases this actually produces a superior plan,
IMO, with less data needing to be transmitted and returned; so we probably
ought to think harder about whether we should ship tlist expressions at
all when they don't contain any foreign Vars or Aggs. But that's an
optimization not a bug fix so I left it for later. One case where this
produces an inferior plan is where the expression in question is actually
a GROUP BY expression: then the restriction prevents us from using remote
grouping. It might be possible to work around that (since that would
reduce to group-by-a-constant on the remote side); but it seems like a
pretty unlikely corner case, so I'm not sure it's worth expending effort
solely to improve that. In any case the right long-term answer is to fix
the API as sketched above, and then revert this hack.
Per bug #15781 from Sean Johnston. Back-patch to v10 where the problem
was introduced.
Discussion: https://postgr.es/m/15781-2601b1002bad087c@postgresql.org
Commit 3d956d9562 added support for update row movement in postgres_fdw.
This patch fixes the following issues introduced by that commit:
* When a remote partition chosen to insert routed rows into was also an
UPDATE subplan target rel that would be updated later, the UPDATE that
used a direct modification plan modified those routed rows incorrectly
because those routed rows were visible to the later UPDATE command.
The right fix for this would be to have some way in postgres_fdw in
which the later UPDATE command ignores those routed rows, but it seems
hard to do so with the current infrastructure. For now throw an error
in that case.
* When a remote partition chosen to insert routed rows into was also an
UPDATE subplan target rel, fmstate created for the UPDATE that used a
non-direct modification plan was mistakenly overridden by another
fmstate created for inserting those routed rows into the partition.
This caused 1) server crash when the partition would be updated later,
and 2) resource leak when the partition had been already updated. To
avoid that, adjust the treatment of the fmstate for the inserting. As
for #1, since we would also have the incorrectness issue as mentioned
above, error out in that case as well.
Update the docs to mention that postgres_fdw currently does not handle
the case where a remote partition chosen to insert a routed row into is
also an UPDATE subplan target rel that will be updated later.
Author: Amit Langote and Etsuro Fujita
Reviewed-by: Amit Langote
Backpatch-through: 11 where row movement in postgres_fdw was added
Discussion: https://postgr.es/m/21e7eaa4-0d4d-20c2-a1f7-c7e96f4ce440@lab.ntt.co.jp
As reported by Tom, when ExecStoreMinimalTuple() had to perform a
conversion to store the minimal tuple in the slot, it forgot to
respect the shouldFree flag, and leaked the tuple into the current
memory context if true. Fix that by freeing the tuple in that case.
Looking at the relevant code made me (Andres) realize that not having
the shouldFree parameter to ExecForceStoreHeapTuple() was a bad
idea. Some callers had to locally implement the necessary logic, and
in one case it was missing, creating a potential per-group leak in
non-hashed aggregation.
The choice to not free the tuple in ExecComputeStoredGenerated() is
not pretty, but not introduced by this commit - I'll start a separate
discussion about it.
Reported-By: Tom Lane
Discussion: https://postgr.es/m/366.1555382816@sss.pgh.pa.us
The upper-planner pathification allows FDWs to arrange to push down
different types of upper-stage operations to the remote side. This
commit teaches postgres_fdw to do it for the (FINAL, NULL) upperrel,
which is responsible for doing LockRows, LIMIT, and/or ModifyTable.
This provides the ability for postgres_fdw to handle SELECT commands
so that it 1) skips the LockRows step (if any) (note that this is
safe since it performs early locking) and 2) pushes down the LIMIT
and/or OFFSET restrictions (if any) to the remote side. This doesn't
handle the INSERT/UPDATE/DELETE cases.
Author: Etsuro Fujita
Reviewed-By: Antonin Houska and Jeff Janes
Discussion: https://postgr.es/m/87pnz1aby9.fsf@news-spur.riddles.org.uk
The upper-planner pathification allows FDWs to arrange to push down
different types of upper-stage operations to the remote side. This
commit teaches postgres_fdw to do it for the (ORDERED, NULL) upperrel,
which is responsible for evaluating the query's ORDER BY ordering.
Since postgres_fdw is already able to evaluate that ordering remotely
for foreign baserels and foreign joinrels (see commit aa09cd242f et al.),
this adds support for that for foreign grouping relations.
Author: Etsuro Fujita
Reviewed-By: Antonin Houska and Jeff Janes
Discussion: https://postgr.es/m/87pnz1aby9.fsf@news-spur.riddles.org.uk
This is an SQL-standard feature that allows creating columns that are
computed from expressions rather than assigned, similar to a view or
materialized view but on a column basis.
This implements one kind of generated column: stored (computed on
write). Another kind, virtual (computed on read), is planned for the
future, and some room is left for it.
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Pavel Stehule <pavel.stehule@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/b151f851-4019-bdb1-699e-ebab07d2f40a@2ndquadrant.com
In preparation for abstracting table storage, convert trigger.c to
track tuples in slots. Which also happens to make code calling
triggers simpler.
As the calling interface for triggers themselves is not changed in
this patch, HeapTuples still are extracted from the slot at that
time. But that's handled solely inside trigger.c, not visible to
callers. It's quite likely that we'll want to revise the external
trigger interface, but that's a separate large project.
As part of this work the slots used for old/new/return tuples are
moved from EState into ResultRelInfo, as different updated tables
might need different slots. The slots are now also now created
on-demand, which is good both from an efficiency POV, but also makes
the modifying code simpler.
Author: Andres Freund, Amit Khandekar and Ashutosh Bapat
Discussion: https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de
Add support function requests for estimating the selectivity, cost,
and number of result rows (if a SRF) of the target function.
The lack of a way to estimate selectivity of a boolean-returning
function in WHERE has been a recognized deficiency of the planner
since Berkeley days. This commit finally fixes it.
In addition, non-constant estimates of cost and number of output
rows are now possible. We still fall back to looking at procost
and prorows if the support function doesn't service the request,
of course.
To make concrete use of the possibility of estimating output rowcount
for SRFs, this commit adds support functions for array_unnest(anyarray)
and the integer variants of generate_series; the lack of plausible
rowcount estimates for those, even when it's obvious to a human,
has been a repeated subject of complaints. Obviously, much more
could now be done in this line, but I'm mostly just trying to get
the infrastructure in place.
Discussion: https://postgr.es/m/15193.1548028093@sss.pgh.pa.us
Up to now postgres_fdw has been using create_foreignscan_path() to
generate not only base-relation paths, but also paths for foreign joins
and foreign upperrels. This is wrong, because create_foreignscan_path()
calls get_baserel_parampathinfo() which will only do the right thing for
baserels. It accidentally fails to fail for unparameterized paths, which
are the only ones postgres_fdw (thought it) was handling, but we really
need different APIs for the baserel and join cases.
In HEAD, the best thing to do seems to be to split up the baserel,
joinrel, and upperrel cases into three functions so that they can
have different APIs. I haven't actually given create_foreign_join_path
a different API in this commit: we should spend a bit of time thinking
about just what we want to do there, since perhaps FDWs would want to
do something different from the build-up-a-join-pairwise approach that
get_joinrel_parampathinfo expects. In the meantime, since postgres_fdw
isn't prepared to generate parameterized joins anyway, just give it a
defense against trying to plan joins with lateral refs.
In addition (and this is what triggered this whole mess) fix bug #15613
from Srinivasan S A, by teaching file_fdw and postgres_fdw that plain
baserel foreign paths still have outer refs if the relation has
lateral_relids. Add some assertions in relnode.c to catch future
occurrences of the same error --- in particular, to catch other FDWs
doing that, but also as backstop against core-code mistakes like the
one fixed by commit bdd9a99aa.
Bug #15613 also needs to be fixed in the back branches, but the
appropriate fix will look quite a bit different there, since we don't
want to assume that existing FDWs get the word right away.
Discussion: https://postgr.es/m/15613-092be1be9576c728@postgresql.org
Create a new header optimizer/optimizer.h, which exposes just the
planner functions that can be used "at arm's length", without need
to access Paths or the other planner-internal data structures defined
in nodes/relation.h. This is intended to provide the whole planner
API seen by most of the rest of the system; although FDWs still need
to use additional stuff, and more thought is also needed about just
what selfuncs.c should rely on.
The main point of doing this now is to limit the amount of new
#include baggage that will be needed by "planner support functions",
which I expect to introduce later, and which will be in relevant
datatype modules rather than anywhere near the planner.
This commit just moves relevant declarations into optimizer.h from
other header files (a couple of which go away because everything
got moved), and adjusts #include lists to match. There's further
cleanup that could be done if we want to decide that some stuff
being exposed by optimizer.h doesn't belong in the planner at all,
but I'll leave that for another day.
Discussion: https://postgr.es/m/11460.1548706639@sss.pgh.pa.us
estimate_path_cost_size() failed to re-use cached costs when the cached
startup/total cost was 0, so it calculated the costs redundantly.
This is an oversight in commit aa09cd242f; but apply the patch to HEAD
only because there are no reports of actual trouble from that.
Author: Etsuro Fujita
Discussion: https://postgr.es/m/5C4AF3F3.4060409%40lab.ntt.co.jp
Previously, estimate_path_cost_size() didn't account for tlist eval
costs, except when costing a foreign-grouping path using local
statistics, but such costs should be accounted for when costing that path
using remote estimates, because some of the tlist expressions might be
evaluated locally. Also, such costs should be accounted for in the case
of a foreign-scan or foreign-join path, because the tlist might contain
PlaceHolderVars, which postgres_fdw currently evaluates locally.
This also fixes an oversight in my commit f8f6e44676.
Like that commit, apply this to HEAD only to avoid destabilizing existing
plan choices.
Author: Etsuro Fujita
Discussion: https://postgr.es/m/5BFD3EAD.2060301%40lab.ntt.co.jp
postgresExecForeignInsert(), postgresExecForeignUpdate(), and
postgresExecForeignDelete() are coded almost identically, except that
postgresExecForeignInsert() does not need CTID. Extract that code into
a separate function and use it in all the three function implementations.
Author: Ashutosh Bapat
Reviewed-By: Michael Paquier
Discussion: https://postgr.es/m/CAFjFpRcz8yoY7cBTYofcrCLwjaDeCcGKyTUivUbRiA57y3v-bw%40mail.gmail.com
heapam.h previously was included in a number of widely used
headers (e.g. execnodes.h, indirectly in executor.h, ...). That's
problematic on its own, as heapam.h contains a lot of low-level
details that don't need to be exposed that widely, but becomes more
problematic with the upcoming introduction of pluggable table storage
- it seems inappropriate for heapam.h to be included that widely
afterwards.
heapam.h was largely only included in other headers to get the
HeapScanDesc typedef (which was defined in heapam.h, even though
HeapScanDescData is defined in relscan.h). The better solution here
seems to be to just use the underlying struct (forward declared where
necessary). Similar for BulkInsertState.
Another problem was that LockTupleMode was used in executor.h - parts
of the file tried to cope without heapam.h, but due to the fact that
it indirectly included it, several subsequent violations of that goal
were not not noticed. We could just reuse the approach of declaring
parameters as int, but it seems nicer to move LockTupleMode to
lockoptions.h - that's not a perfect location, but also doesn't seem
bad.
As a number of files relied on implicitly included heapam.h, a
significant number of files grew an explicit include. It's quite
probably that a few external projects will need to do the same.
Author: Andres Freund
Reviewed-By: Alvaro Herrera
Discussion: https://postgr.es/m/20190114000701.y4ttcb74jpskkcfb@alap3.anarazel.de
postgres_fdw's postgresGetForeignPlan() assumes without checking that the
outer_plan it's given for a join relation must have a NestLoop, MergeJoin,
or HashJoin node at the top. That's been wrong at least since commit
4bbf6edfb (which could cause insertion of a Sort node on top) and it seems
like a pretty unsafe thing to Just Assume even without that.
Through blind good fortune, this doesn't seem to have any worse
consequences today than strange EXPLAIN output, but it's clearly trouble
waiting to happen.
To fix, test the node type explicitly before touching Join-specific
fields, and avoid jamming the new tlist into a node type that can't
do projection. Export a new support function from createplan.c
to avoid building low-level knowledge about the latter into FDWs.
Back-patch to 9.6 where the faulty coding was added. Note that the
associated regression test cases don't show any changes before v11,
apparently because the tests back-patched with 4bbf6edfb don't actually
exercise the problem case before then (there's no top-level Sort
in those plans).
Discussion: https://postgr.es/m/8946.1544644803@sss.pgh.pa.us
Etsuro Fujita