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Fix contrib/dblink to handle inconsistent DateStyle/IntervalStyle saf…

…ely.

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
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tglsfdc committed Mar 22, 2013
1 parent 549dae0 commit 8a3b6772aedbd95557ab1fc489ddf007ac9d405d
Showing with 372 additions and 5 deletions.
  1. +100 −5 contrib/dblink/dblink.c
  2. +176 −0 contrib/dblink/expected/dblink.out
  3. +96 −0 contrib/dblink/sql/dblink.sql
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@@ -53,6 +53,7 @@
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
+#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/rel.h"
@@ -86,7 +87,8 @@ typedef struct storeInfo
*/
static Datum dblink_record_internal(FunctionCallInfo fcinfo, bool is_async);
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,
PGconn *conn,
const char *conname,
@@ -118,6 +120,8 @@ static void validate_pkattnums(Relation rel,
int **pkattnums, int *pknumatts);
static bool is_valid_dblink_option(const PQconninfoOption *options,
const char *option, Oid context);
+static int applyRemoteGucs(PGconn *conn);
+static void restoreLocalGucs(int nestlevel);
/* Global */
static remoteConn *pconn = NULL;
@@ -605,7 +609,7 @@ dblink_fetch(PG_FUNCTION_ARGS)
errmsg("cursor \"%s\" does not exist", curname)));
}
- materializeResult(fcinfo, res);
+ materializeResult(fcinfo, conn, res);
return (Datum) 0;
}
@@ -750,7 +754,7 @@ dblink_record_internal(FunctionCallInfo fcinfo, bool is_async)
}
else
{
- materializeResult(fcinfo, res);
+ materializeResult(fcinfo, conn, res);
}
}
}
@@ -806,7 +810,7 @@ prepTuplestoreResult(FunctionCallInfo fcinfo)
* The PGresult will be released in this function.
*/
static void
-materializeResult(FunctionCallInfo fcinfo, PGresult *res)
+materializeResult(FunctionCallInfo fcinfo, PGconn *conn, PGresult *res)
{
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
@@ -816,7 +820,7 @@ materializeResult(FunctionCallInfo fcinfo, PGresult *res)
PG_TRY();
{
TupleDesc tupdesc;
- bool is_sql_cmd = false;
+ bool is_sql_cmd;
int ntuples;
int nfields;
@@ -877,13 +881,18 @@ materializeResult(FunctionCallInfo fcinfo, PGresult *res)
if (ntuples > 0)
{
AttInMetadata *attinmeta;
+ int nestlevel = -1;
Tuplestorestate *tupstore;
MemoryContext oldcontext;
int row;
char **values;
attinmeta = TupleDescGetAttInMetadata(tupdesc);
+ /* Set GUCs to ensure we read GUC-sensitive data types correctly */
+ if (!is_sql_cmd)
+ nestlevel = applyRemoteGucs(conn);
+
oldcontext = MemoryContextSwitchTo(
rsinfo->econtext->ecxt_per_query_memory);
tupstore = tuplestore_begin_heap(true, false, work_mem);
@@ -920,6 +929,9 @@ materializeResult(FunctionCallInfo fcinfo, PGresult *res)
tuplestore_puttuple(tupstore, tuple);
}
+ /* clean up GUC settings, if we changed any */
+ restoreLocalGucs(nestlevel);
+
/* clean up and return the tuplestore */
tuplestore_donestoring(tupstore);
}
@@ -1053,6 +1065,7 @@ static PGresult *
storeQueryResult(storeInfo *sinfo, PGconn *conn, const char *sql)
{
bool first = true;
+ int nestlevel = -1;
PGresult *res;
if (!PQsendQuery(conn, sql))
@@ -1072,6 +1085,15 @@ storeQueryResult(storeInfo *sinfo, PGconn *conn, const char *sql)
if (PQresultStatus(sinfo->cur_res) == PGRES_SINGLE_TUPLE)
{
/* 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);
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 */
res = sinfo->last_res;
sinfo->last_res = NULL;
@@ -2898,3 +2923,73 @@ is_valid_dblink_option(const PQconninfoOption *options, const char *option,
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);
+}
@@ -913,3 +913,179 @@ SELECT dblink_build_sql_delete('test_dropped', '1', 1,
DELETE FROM test_dropped WHERE id = '2'
(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;
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