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Rethink plpgsql's way of handling SPI execution during an exception block.
We don't really want to start a new SPI connection, just keep using the old one; otherwise we have memory management problems as illustrated by John Kennedy's bug report of today. This requires a bit of a hack to ensure the SPI stack state is properly restored, but then again what we were doing before was a hack too, strictly speaking. Add a regression test to cover this case.
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5 files changed

+72
-20
lines changed

5 files changed

+72
-20
lines changed

‎src/backend/executor/spi.c

Lines changed: 9 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/executor/spi.c,v 1.131 2004/10/13 01:25:10 neilc Exp $
11+
* $PostgreSQL: pgsql/src/backend/executor/spi.c,v 1.132 2004/11/16 18:10:13 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -270,6 +270,14 @@ SPI_pop(void)
270270
_SPI_curid--;
271271
}
272272

273+
/* Restore state of SPI stack after aborting a subtransaction */
274+
void
275+
SPI_restore_connection(void)
276+
{
277+
Assert(_SPI_connected >= 0);
278+
_SPI_curid = _SPI_connected - 1;
279+
}
280+
273281
/* Parse, plan, and execute a querystring */
274282
int
275283
SPI_execute(const char *src, bool read_only, int tcount)

‎src/include/executor/spi.h

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@
22
*
33
* spi.h
44
*
5-
* $PostgreSQL: pgsql/src/include/executor/spi.h,v 1.49 2004/09/16 16:58:40 tgl Exp $
5+
* $PostgreSQL: pgsql/src/include/executor/spi.h,v 1.50 2004/11/16 18:10:13 tgl Exp $
66
*
77
*-------------------------------------------------------------------------
88
*/
@@ -81,6 +81,7 @@ extern int SPI_connect(void);
8181
extern int SPI_finish(void);
8282
extern void SPI_push(void);
8383
extern void SPI_pop(void);
84+
extern void SPI_restore_connection(void);
8485
extern int SPI_execute(const char *src, bool read_only, int tcount);
8586
extern int SPI_execute_plan(void *plan, Datum *Values, const char *Nulls,
8687
bool read_only, int tcount);

‎src/pl/plpgsql/src/pl_exec.c

Lines changed: 13 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
* procedural language
44
*
55
* IDENTIFICATION
6-
* $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.120 2004/09/16 16:58:44 tgl Exp $
6+
* $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.121 2004/11/16 18:10:14 tgl Exp $
77
*
88
* This software is copyrighted by Jan Wieck - Hamburg.
99
*
@@ -899,20 +899,11 @@ exec_stmt_block(PLpgSQL_execstate *estate, PLpgSQL_stmt_block *block)
899899
MemoryContext oldcontext = CurrentMemoryContext;
900900
ResourceOwner oldowner = CurrentResourceOwner;
901901
volatile bool caught = false;
902-
int xrc;
903902

904-
/*
905-
* Start a subtransaction, and re-connect to SPI within it
906-
*/
907-
SPI_push();
908903
BeginInternalSubTransaction(NULL);
909904
/* Want to run statements inside function's memory context */
910905
MemoryContextSwitchTo(oldcontext);
911906

912-
if ((xrc = SPI_connect()) != SPI_OK_CONNECT)
913-
elog(ERROR, "SPI_connect failed: %s",
914-
SPI_result_code_string(xrc));
915-
916907
PG_TRY();
917908
{
918909
rc = exec_stmts(estate, block->body);
@@ -928,12 +919,17 @@ exec_stmt_block(PLpgSQL_execstate *estate, PLpgSQL_stmt_block *block)
928919
edata = CopyErrorData();
929920
FlushErrorState();
930921

931-
/* Abort the inner transaction (and inner SPI connection) */
922+
/* Abort the inner transaction */
932923
RollbackAndReleaseCurrentSubTransaction();
933924
MemoryContextSwitchTo(oldcontext);
934925
CurrentResourceOwner = oldowner;
935926

936-
SPI_pop();
927+
/*
928+
* If AtEOSubXact_SPI() popped any SPI context of the subxact,
929+
* it will have left us in a disconnected state. We need this
930+
* hack to return to connected state.
931+
*/
932+
SPI_restore_connection();
937933

938934
/* Look for a matching exception handler */
939935
exceptions = block->exceptions;
@@ -960,15 +956,14 @@ exec_stmt_block(PLpgSQL_execstate *estate, PLpgSQL_stmt_block *block)
960956
/* Commit the inner transaction, return to outer xact context */
961957
if (!caught)
962958
{
963-
if ((xrc = SPI_finish()) != SPI_OK_FINISH)
964-
elog(ERROR, "SPI_finish failed: %s",
965-
SPI_result_code_string(xrc));
966-
967959
ReleaseCurrentSubTransaction();
968960
MemoryContextSwitchTo(oldcontext);
969961
CurrentResourceOwner = oldowner;
970-
971-
SPI_pop();
962+
/*
963+
* AtEOSubXact_SPI() should not have popped any SPI context,
964+
* but just in case it did, make sure we remain connected.
965+
*/
966+
SPI_restore_connection();
972967
}
973968
}
974969
else

‎src/test/regress/expected/plpgsql.out

Lines changed: 30 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1931,6 +1931,36 @@ select * from foo;
19311931
20
19321932
(2 rows)
19331933

1934+
-- Test for pass-by-ref values being stored in proper context
1935+
create function test_variable_storage() returns text as $$
1936+
declare x text;
1937+
begin
1938+
x := '1234';
1939+
begin
1940+
x := x || '5678';
1941+
-- force error inside subtransaction SPI context
1942+
perform trap_zero_divide(-100);
1943+
exception
1944+
when others then
1945+
x := x || '9012';
1946+
end;
1947+
return x;
1948+
end$$ language plpgsql;
1949+
select test_variable_storage();
1950+
NOTICE: should see this
1951+
CONTEXT: SQL statement "SELECT trap_zero_divide(-100)"
1952+
PL/pgSQL function "test_variable_storage" line 7 at perform
1953+
NOTICE: should see this only if -100 <> 0
1954+
CONTEXT: SQL statement "SELECT trap_zero_divide(-100)"
1955+
PL/pgSQL function "test_variable_storage" line 7 at perform
1956+
NOTICE: should see this only if -100 fits in smallint
1957+
CONTEXT: SQL statement "SELECT trap_zero_divide(-100)"
1958+
PL/pgSQL function "test_variable_storage" line 7 at perform
1959+
test_variable_storage
1960+
-----------------------
1961+
123456789012
1962+
(1 row)
1963+
19341964
--
19351965
-- test foreign key error trapping
19361966
--

‎src/test/regress/sql/plpgsql.sql

Lines changed: 18 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1696,6 +1696,24 @@ reset statement_timeout;
16961696

16971697
select * from foo;
16981698

1699+
-- Test for pass-by-ref values being stored in proper context
1700+
create function test_variable_storage() returns text as $$
1701+
declare x text;
1702+
begin
1703+
x := '1234';
1704+
begin
1705+
x := x || '5678';
1706+
-- force error inside subtransaction SPI context
1707+
perform trap_zero_divide(-100);
1708+
exception
1709+
when others then
1710+
x := x || '9012';
1711+
end;
1712+
return x;
1713+
end$$ language plpgsql;
1714+
1715+
select test_variable_storage();
1716+
16991717
--
17001718
-- test foreign key error trapping
17011719
--

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