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Fix contrib/dblink to handle inconsistent DateStyle/IntervalStyle safely.

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If the remote database's settings of these GUCs are different from ours,
ambiguous datetime values may be read incorrectly.  To fix, temporarily
adopt the remote server's settings while we ingest a query result.

This is not a complete fix, since it doesn't do anything about ambiguous
values in commands sent to the remote server; but there seems little we
can do about that end of it given dblink's entirely textual API for
transmitted commands.

Back-patch to 9.2.  The hazard exists in all versions, but this patch
would need more work to apply before 9.2.  Given the lack of field
complaints about this issue, it doesn't seem worth the effort at present.

Daniel Farina and Tom Lane
pull/4/head
Tom Lane 12 years ago
parent 549dae0352
commit 8a3b6772ae
3 changed files with 372 additions and 5 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
Show Stats Download Patch File Download Diff File
  1. 105
      contrib/dblink/dblink.c
  2. 176
      contrib/dblink/expected/dblink.out
  3. 96
      contrib/dblink/sql/dblink.sql

105
contrib/dblink/dblink.c
Unescape View File

@ -53,6 +53,7 @@
#include "utils/acl.h" #include "utils/acl.h"
#include "utils/builtins.h" #include "utils/builtins.h"
#include "utils/fmgroids.h" #include "utils/fmgroids.h"
#include "utils/guc.h"
#include "utils/lsyscache.h" #include "utils/lsyscache.h"
#include "utils/memutils.h" #include "utils/memutils.h"
#include "utils/rel.h" #include "utils/rel.h"
@ -86,7 +87,8 @@ typedef struct storeInfo
*/ */
static Datum dblink_record_internal(FunctionCallInfo fcinfo, bool is_async); static Datum dblink_record_internal(FunctionCallInfo fcinfo, bool is_async);
static void prepTuplestoreResult(FunctionCallInfo fcinfo); static void prepTuplestoreResult(FunctionCallInfo fcinfo);
static void materializeResult(FunctionCallInfo fcinfo, PGresult *res); static void materializeResult(FunctionCallInfo fcinfo, PGconn *conn,
PGresult *res);
static void materializeQueryResult(FunctionCallInfo fcinfo, static void materializeQueryResult(FunctionCallInfo fcinfo,
PGconn *conn, PGconn *conn,
const char *conname, const char *conname,
@ -118,6 +120,8 @@ static void validate_pkattnums(Relation rel,
int **pkattnums, int *pknumatts); int **pkattnums, int *pknumatts);
static bool is_valid_dblink_option(const PQconninfoOption *options, static bool is_valid_dblink_option(const PQconninfoOption *options,
const char *option, Oid context); const char *option, Oid context);
static int applyRemoteGucs(PGconn *conn);
static void restoreLocalGucs(int nestlevel);
/* Global */ /* Global */
static remoteConn *pconn = NULL; static remoteConn *pconn = NULL;
@ -605,7 +609,7 @@ dblink_fetch(PG_FUNCTION_ARGS)
errmsg("cursor \"%s\" does not exist", curname))); errmsg("cursor \"%s\" does not exist", curname)));
} }
materializeResult(fcinfo, res); materializeResult(fcinfo, conn, res);
return (Datum) 0; return (Datum) 0;
} }
@ -750,7 +754,7 @@ dblink_record_internal(FunctionCallInfo fcinfo, bool is_async)
} }
else else
{ {
materializeResult(fcinfo, res); materializeResult(fcinfo, conn, res);
} }
} }
} }
@ -806,7 +810,7 @@ prepTuplestoreResult(FunctionCallInfo fcinfo)
* The PGresult will be released in this function. * The PGresult will be released in this function.
*/ */
static void static void
materializeResult(FunctionCallInfo fcinfo, PGresult *res) materializeResult(FunctionCallInfo fcinfo, PGconn *conn, PGresult *res)
{ {
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo; ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
@ -816,7 +820,7 @@ materializeResult(FunctionCallInfo fcinfo, PGresult *res)
PG_TRY(); PG_TRY();
{ {
TupleDesc tupdesc; TupleDesc tupdesc;
bool is_sql_cmd = false; bool is_sql_cmd;
int ntuples; int ntuples;
int nfields; int nfields;
@ -877,6 +881,7 @@ materializeResult(FunctionCallInfo fcinfo, PGresult *res)
if (ntuples > 0) if (ntuples > 0)
{ {
AttInMetadata *attinmeta; AttInMetadata *attinmeta;
int nestlevel = -1;
Tuplestorestate *tupstore; Tuplestorestate *tupstore;
MemoryContext oldcontext; MemoryContext oldcontext;
int row; int row;
@ -884,6 +889,10 @@ materializeResult(FunctionCallInfo fcinfo, PGresult *res)
attinmeta = TupleDescGetAttInMetadata(tupdesc); attinmeta = TupleDescGetAttInMetadata(tupdesc);
/* Set GUCs to ensure we read GUC-sensitive data types correctly */
if (!is_sql_cmd)
nestlevel = applyRemoteGucs(conn);
oldcontext = MemoryContextSwitchTo( oldcontext = MemoryContextSwitchTo(
rsinfo->econtext->ecxt_per_query_memory); rsinfo->econtext->ecxt_per_query_memory);
tupstore = tuplestore_begin_heap(true, false, work_mem); tupstore = tuplestore_begin_heap(true, false, work_mem);
@ -920,6 +929,9 @@ materializeResult(FunctionCallInfo fcinfo, PGresult *res)
tuplestore_puttuple(tupstore, tuple); tuplestore_puttuple(tupstore, tuple);
} }
/* clean up GUC settings, if we changed any */
restoreLocalGucs(nestlevel);
/* clean up and return the tuplestore */ /* clean up and return the tuplestore */
tuplestore_donestoring(tupstore); tuplestore_donestoring(tupstore);
} }
@ -1053,6 +1065,7 @@ static PGresult *
storeQueryResult(storeInfo *sinfo, PGconn *conn, const char *sql) storeQueryResult(storeInfo *sinfo, PGconn *conn, const char *sql)
{ {
bool first = true; bool first = true;
int nestlevel = -1;
PGresult *res; PGresult *res;
if (!PQsendQuery(conn, sql)) if (!PQsendQuery(conn, sql))
@ -1072,6 +1085,15 @@ storeQueryResult(storeInfo *sinfo, PGconn *conn, const char *sql)
if (PQresultStatus(sinfo->cur_res) == PGRES_SINGLE_TUPLE) if (PQresultStatus(sinfo->cur_res) == PGRES_SINGLE_TUPLE)
{ {
/* got one row from possibly-bigger resultset */ /* got one row from possibly-bigger resultset */
/*
* Set GUCs to ensure we read GUC-sensitive data types correctly.
* We shouldn't do this until we have a row in hand, to ensure
* libpq has seen any earlier ParameterStatus protocol messages.
*/
if (first && nestlevel < 0)
nestlevel = applyRemoteGucs(conn);
storeRow(sinfo, sinfo->cur_res, first); storeRow(sinfo, sinfo->cur_res, first);
PQclear(sinfo->cur_res); PQclear(sinfo->cur_res);
@ -1092,6 +1114,9 @@ storeQueryResult(storeInfo *sinfo, PGconn *conn, const char *sql)
} }
} }
/* clean up GUC settings, if we changed any */
restoreLocalGucs(nestlevel);
/* return last_res */ /* return last_res */
res = sinfo->last_res; res = sinfo->last_res;
sinfo->last_res = NULL; sinfo->last_res = NULL;
@ -2898,3 +2923,73 @@ is_valid_dblink_option(const PQconninfoOption *options, const char *option,
return true; return true;
} }
/*
* Copy the remote session's values of GUCs that affect datatype I/O
* and apply them locally in a new GUC nesting level. Returns the new
* nestlevel (which is needed by restoreLocalGucs to undo the settings),
* or -1 if no new nestlevel was needed.
*
* We use the equivalent of a function SET option to allow the settings to
* persist only until the caller calls restoreLocalGucs. If an error is
* thrown in between, guc.c will take care of undoing the settings.
*/
static int
applyRemoteGucs(PGconn *conn)
{
static const char *const GUCsAffectingIO[] = {
"DateStyle",
"IntervalStyle"
};
int nestlevel = -1;
int i;
for (i = 0; i < lengthof(GUCsAffectingIO); i++)
{
const char *gucName = GUCsAffectingIO[i];
const char *remoteVal = PQparameterStatus(conn, gucName);
const char *localVal;
/*
* If the remote server is pre-8.4, it won't have IntervalStyle, but
* that's okay because its output format won't be ambiguous. So just
* skip the GUC if we don't get a value for it. (We might eventually
* need more complicated logic with remote-version checks here.)
*/
if (remoteVal == NULL)
continue;
/*
* Avoid GUC-setting overhead if the remote and local GUCs already
* have the same value.
*/
localVal = GetConfigOption(gucName, false, false);
Assert(localVal != NULL);
if (strcmp(remoteVal, localVal) == 0)
continue;
/* Create new GUC nest level if we didn't already */
if (nestlevel < 0)
nestlevel = NewGUCNestLevel();
/* Apply the option (this will throw error on failure) */
(void) set_config_option(gucName, remoteVal,
PGC_USERSET, PGC_S_SESSION,
GUC_ACTION_SAVE, true, 0);
}
return nestlevel;
}
/*
* Restore local GUCs after they have been overlaid with remote settings.
*/
static void
restoreLocalGucs(int nestlevel)
{
/* Do nothing if no new nestlevel was created */
if (nestlevel > 0)
AtEOXact_GUC(true, nestlevel);
}

176
contrib/dblink/expected/dblink.out
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@ -913,3 +913,179 @@ SELECT dblink_build_sql_delete('test_dropped', '1', 1,
DELETE FROM test_dropped WHERE id = '2' DELETE FROM test_dropped WHERE id = '2'
(1 row) (1 row)
-- test local mimicry of remote GUC values that affect datatype I/O
SET datestyle = ISO, MDY;
SET intervalstyle = postgres;
SET timezone = UTC;
SELECT dblink_connect('myconn','dbname=contrib_regression');
dblink_connect
----------------
OK
(1 row)
SELECT dblink_exec('myconn', 'SET datestyle = GERMAN, DMY;');
dblink_exec
-------------
SET
(1 row)
-- single row synchronous case
SELECT *
FROM dblink('myconn',
'SELECT * FROM (VALUES (''12.03.2013 00:00:00+00'')) t')
AS t(a timestamptz);
a
------------------------
2013-03-12 00:00:00+00
(1 row)
-- multi-row synchronous case
SELECT *
FROM dblink('myconn',
'SELECT * FROM
(VALUES (''12.03.2013 00:00:00+00''),
(''12.03.2013 00:00:00+00'')) t')
AS t(a timestamptz);
a
------------------------
2013-03-12 00:00:00+00
2013-03-12 00:00:00+00
(2 rows)
-- single-row asynchronous case
SELECT *
FROM dblink_send_query('myconn',
'SELECT * FROM
(VALUES (''12.03.2013 00:00:00+00'')) t');
dblink_send_query
-------------------
1
(1 row)
CREATE TEMPORARY TABLE result AS
(SELECT * from dblink_get_result('myconn') as t(t timestamptz))
UNION ALL
(SELECT * from dblink_get_result('myconn') as t(t timestamptz));
SELECT * FROM result;
t
------------------------
2013-03-12 00:00:00+00
(1 row)
DROP TABLE result;
-- multi-row asynchronous case
SELECT *
FROM dblink_send_query('myconn',
'SELECT * FROM
(VALUES (''12.03.2013 00:00:00+00''),
(''12.03.2013 00:00:00+00'')) t');
dblink_send_query
-------------------
1
(1 row)
CREATE TEMPORARY TABLE result AS
(SELECT * from dblink_get_result('myconn') as t(t timestamptz))
UNION ALL
(SELECT * from dblink_get_result('myconn') as t(t timestamptz))
UNION ALL
(SELECT * from dblink_get_result('myconn') as t(t timestamptz));
SELECT * FROM result;
t
------------------------
2013-03-12 00:00:00+00
2013-03-12 00:00:00+00
(2 rows)
DROP TABLE result;
-- Try an ambiguous interval
SELECT dblink_exec('myconn', 'SET intervalstyle = sql_standard;');
dblink_exec
-------------
SET
(1 row)
SELECT *
FROM dblink('myconn',
'SELECT * FROM (VALUES (''-1 2:03:04'')) i')
AS i(i interval);
i
-------------------
-1 days -02:03:04
(1 row)
-- Try swapping to another format to ensure the GUCs are tracked
-- properly through a change.
CREATE TEMPORARY TABLE result (t timestamptz);
SELECT dblink_exec('myconn', 'SET datestyle = ISO, MDY;');
dblink_exec
-------------
SET
(1 row)
INSERT INTO result
SELECT *
FROM dblink('myconn',
'SELECT * FROM (VALUES (''03.12.2013 00:00:00+00'')) t')
AS t(a timestamptz);
SELECT dblink_exec('myconn', 'SET datestyle = GERMAN, DMY;');
dblink_exec
-------------
SET
(1 row)
INSERT INTO result
SELECT *
FROM dblink('myconn',
'SELECT * FROM (VALUES (''12.03.2013 00:00:00+00'')) t')
AS t(a timestamptz);
SELECT * FROM result;
t
------------------------
2013-03-12 00:00:00+00
2013-03-12 00:00:00+00
(2 rows)
DROP TABLE result;
-- Check error throwing in dblink_fetch
SELECT dblink_open('myconn','error_cursor',
'SELECT * FROM (VALUES (''1''), (''not an int'')) AS t(text);');
dblink_open
-------------
OK
(1 row)
SELECT *
FROM dblink_fetch('myconn','error_cursor', 1) AS t(i int);
i
---
1
(1 row)
SELECT *
FROM dblink_fetch('myconn','error_cursor', 1) AS t(i int);
ERROR: invalid input syntax for integer: "not an int"
-- Make sure that the local settings have retained their values in spite
-- of shenanigans on the connection.
SHOW datestyle;
DateStyle
-----------
ISO, MDY
(1 row)
SHOW intervalstyle;
IntervalStyle
---------------
postgres
(1 row)
-- Clean up GUC-setting tests
SELECT dblink_disconnect('myconn');
dblink_disconnect
-------------------
OK
(1 row)
RESET datestyle;
RESET intervalstyle;
RESET timezone;

96
contrib/dblink/sql/dblink.sql
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@ -426,3 +426,99 @@ SELECT dblink_build_sql_update('test_dropped', '1', 1,
SELECT dblink_build_sql_delete('test_dropped', '1', 1, SELECT dblink_build_sql_delete('test_dropped', '1', 1,
ARRAY['2'::TEXT]); ARRAY['2'::TEXT]);
-- test local mimicry of remote GUC values that affect datatype I/O
SET datestyle = ISO, MDY;
SET intervalstyle = postgres;
SET timezone = UTC;
SELECT dblink_connect('myconn','dbname=contrib_regression');
SELECT dblink_exec('myconn', 'SET datestyle = GERMAN, DMY;');
-- single row synchronous case
SELECT *
FROM dblink('myconn',
'SELECT * FROM (VALUES (''12.03.2013 00:00:00+00'')) t')
AS t(a timestamptz);
-- multi-row synchronous case
SELECT *
FROM dblink('myconn',
'SELECT * FROM
(VALUES (''12.03.2013 00:00:00+00''),
(''12.03.2013 00:00:00+00'')) t')
AS t(a timestamptz);
-- single-row asynchronous case
SELECT *
FROM dblink_send_query('myconn',
'SELECT * FROM
(VALUES (''12.03.2013 00:00:00+00'')) t');
CREATE TEMPORARY TABLE result AS
(SELECT * from dblink_get_result('myconn') as t(t timestamptz))
UNION ALL
(SELECT * from dblink_get_result('myconn') as t(t timestamptz));
SELECT * FROM result;
DROP TABLE result;
-- multi-row asynchronous case
SELECT *
FROM dblink_send_query('myconn',
'SELECT * FROM
(VALUES (''12.03.2013 00:00:00+00''),
(''12.03.2013 00:00:00+00'')) t');
CREATE TEMPORARY TABLE result AS
(SELECT * from dblink_get_result('myconn') as t(t timestamptz))
UNION ALL
(SELECT * from dblink_get_result('myconn') as t(t timestamptz))
UNION ALL
(SELECT * from dblink_get_result('myconn') as t(t timestamptz));
SELECT * FROM result;
DROP TABLE result;
-- Try an ambiguous interval
SELECT dblink_exec('myconn', 'SET intervalstyle = sql_standard;');
SELECT *
FROM dblink('myconn',
'SELECT * FROM (VALUES (''-1 2:03:04'')) i')
AS i(i interval);
-- Try swapping to another format to ensure the GUCs are tracked
-- properly through a change.
CREATE TEMPORARY TABLE result (t timestamptz);
SELECT dblink_exec('myconn', 'SET datestyle = ISO, MDY;');
INSERT INTO result
SELECT *
FROM dblink('myconn',
'SELECT * FROM (VALUES (''03.12.2013 00:00:00+00'')) t')
AS t(a timestamptz);
SELECT dblink_exec('myconn', 'SET datestyle = GERMAN, DMY;');
INSERT INTO result
SELECT *
FROM dblink('myconn',
'SELECT * FROM (VALUES (''12.03.2013 00:00:00+00'')) t')
AS t(a timestamptz);
SELECT * FROM result;
DROP TABLE result;
-- Check error throwing in dblink_fetch
SELECT dblink_open('myconn','error_cursor',
'SELECT * FROM (VALUES (''1''), (''not an int'')) AS t(text);');
SELECT *
FROM dblink_fetch('myconn','error_cursor', 1) AS t(i int);
SELECT *
FROM dblink_fetch('myconn','error_cursor', 1) AS t(i int);
-- Make sure that the local settings have retained their values in spite
-- of shenanigans on the connection.
SHOW datestyle;
SHOW intervalstyle;
-- Clean up GUC-setting tests
SELECT dblink_disconnect('myconn');
RESET datestyle;
RESET intervalstyle;
RESET timezone;

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