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Commit1f6a7eb

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Repair unsafe use of shared typecast-lookup table in plpgsql DO blocks.
DO blocks use private simple_eval_estates to avoid intra-transaction memoryleakage, cf commitc7b849a. I had forgotten about that while writingcommit0fc94a5, but it means that expression execution trees createdwithin a DO block disappear immediately on exiting the DO block, and hencecan't safely be linked into plpgsql's session-wide cast hash table.To fix, give a DO block a private cast hash table to go with its privatesimple_eval_estate. This is less efficient than one could wish, sinceDO blocks can no longer share any cast lookup work with other plpgsqlexecution, but it shouldn't be too bad; in any case it's no worse thanwhat happened in DO blocks before commit0fc94a5.Per bug #13571 from Feike Steenbergen. Preliminary analysis byOleksandr Shulgin.
1 parent6942663 commit1f6a7eb

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4 files changed

+71
-28
lines changed

4 files changed

+71
-28
lines changed

‎src/pl/plpgsql/src/pl_exec.c‎

Lines changed: 51 additions & 28 deletions
Original file line numberDiff line numberDiff line change
@@ -98,6 +98,10 @@ static SimpleEcontextStackEntry *simple_econtext_stack = NULL;
9898
*
9999
* The evaluation state trees (cast_exprstate) are managed in the same way as
100100
* simple expressions (i.e., we assume cast expressions are always simple).
101+
*
102+
* As with simple expressions, DO blocks don't use the shared hash table but
103+
* must have their own. This isn't ideal, but we don't want to deal with
104+
* multiple simple_eval_estates within a DO block.
101105
*/
102106
typedefstruct/* lookup key for cast info */
103107
{
@@ -118,8 +122,8 @@ typedef struct/* cast_hash table entry */
118122
LocalTransactionIdcast_lxid;
119123
}plpgsql_CastHashEntry;
120124

121-
staticMemoryContextcast_hash_context=NULL;
122-
staticHTAB*cast_hash=NULL;
125+
staticMemoryContextshared_cast_context=NULL;
126+
staticHTAB*shared_cast_hash=NULL;
123127

124128
/************************************************************
125129
* Local function forward declarations
@@ -283,7 +287,9 @@ static char *format_preparedparamsdata(PLpgSQL_execstate *estate,
283287
* difference that this code is aware of is that for a DO block, we want
284288
* to use a private simple_eval_estate, which is created and passed in by
285289
* the caller. For regular functions, pass NULL, which implies using
286-
* shared_simple_eval_estate.
290+
* shared_simple_eval_estate. (When using a private simple_eval_estate,
291+
* we must also use a private cast hashtable, but that's taken care of
292+
* within plpgsql_estate_setup.)
287293
* ----------
288294
*/
289295
Datum
@@ -3286,6 +3292,8 @@ plpgsql_estate_setup(PLpgSQL_execstate *estate,
32863292
ReturnSetInfo*rsi,
32873293
EState*simple_eval_estate)
32883294
{
3295+
HASHCTLctl;
3296+
32893297
/* this link will be restored at exit from plpgsql_call_handler */
32903298
func->cur_estate=estate;
32913299

@@ -3333,11 +3341,44 @@ plpgsql_estate_setup(PLpgSQL_execstate *estate,
33333341
estate->paramLI->parserSetupArg=NULL;/* filled during use */
33343342
estate->paramLI->numParams=estate->ndatums;
33353343

3336-
/* set up for use of appropriate simple-expression EState */
3344+
/* set up for use of appropriate simple-expression EStateand cast hash*/
33373345
if (simple_eval_estate)
3346+
{
33383347
estate->simple_eval_estate=simple_eval_estate;
3348+
/* Private cast hash just lives in function's main context */
3349+
memset(&ctl,0,sizeof(ctl));
3350+
ctl.keysize=sizeof(plpgsql_CastHashKey);
3351+
ctl.entrysize=sizeof(plpgsql_CastHashEntry);
3352+
ctl.hcxt=CurrentMemoryContext;
3353+
estate->cast_hash=hash_create("PLpgSQL private cast cache",
3354+
16,/* start small and extend */
3355+
&ctl,
3356+
HASH_ELEM |HASH_BLOBS |HASH_CONTEXT);
3357+
estate->cast_hash_context=CurrentMemoryContext;
3358+
}
33393359
else
3360+
{
33403361
estate->simple_eval_estate=shared_simple_eval_estate;
3362+
/* Create the session-wide cast-info hash table if we didn't already */
3363+
if (shared_cast_hash==NULL)
3364+
{
3365+
shared_cast_context=AllocSetContextCreate(TopMemoryContext,
3366+
"PLpgSQL cast info",
3367+
ALLOCSET_DEFAULT_MINSIZE,
3368+
ALLOCSET_DEFAULT_INITSIZE,
3369+
ALLOCSET_DEFAULT_MAXSIZE);
3370+
memset(&ctl,0,sizeof(ctl));
3371+
ctl.keysize=sizeof(plpgsql_CastHashKey);
3372+
ctl.entrysize=sizeof(plpgsql_CastHashEntry);
3373+
ctl.hcxt=shared_cast_context;
3374+
shared_cast_hash=hash_create("PLpgSQL cast cache",
3375+
16,/* start small and extend */
3376+
&ctl,
3377+
HASH_ELEM |HASH_BLOBS |HASH_CONTEXT);
3378+
}
3379+
estate->cast_hash=shared_cast_hash;
3380+
estate->cast_hash_context=shared_cast_context;
3381+
}
33413382

33423383
estate->eval_tuptable=NULL;
33433384
estate->eval_processed=0;
@@ -6014,32 +6055,12 @@ get_cast_hashentry(PLpgSQL_execstate *estate,
60146055
LocalTransactionIdcurlxid;
60156056
MemoryContextoldcontext;
60166057

6017-
/* Create the session-wide cast-info hash table if we didn't already */
6018-
if (cast_hash==NULL)
6019-
{
6020-
HASHCTLctl;
6021-
6022-
cast_hash_context=AllocSetContextCreate(TopMemoryContext,
6023-
"PLpgSQL cast info",
6024-
ALLOCSET_DEFAULT_MINSIZE,
6025-
ALLOCSET_DEFAULT_INITSIZE,
6026-
ALLOCSET_DEFAULT_MAXSIZE);
6027-
memset(&ctl,0,sizeof(ctl));
6028-
ctl.keysize=sizeof(plpgsql_CastHashKey);
6029-
ctl.entrysize=sizeof(plpgsql_CastHashEntry);
6030-
ctl.hcxt=cast_hash_context;
6031-
cast_hash=hash_create("PLpgSQL cast cache",
6032-
16,/* start small and extend */
6033-
&ctl,
6034-
HASH_ELEM |HASH_BLOBS |HASH_CONTEXT);
6035-
}
6036-
60376058
/* Look for existing entry */
60386059
cast_key.srctype=srctype;
60396060
cast_key.dsttype=dsttype;
60406061
cast_key.srctypmod=srctypmod;
60416062
cast_key.dsttypmod=dsttypmod;
6042-
cast_entry= (plpgsql_CastHashEntry*)hash_search(cast_hash,
6063+
cast_entry= (plpgsql_CastHashEntry*)hash_search(estate->cast_hash,
60436064
(void*)&cast_key,
60446065
HASH_FIND,NULL);
60456066

@@ -6124,15 +6145,15 @@ get_cast_hashentry(PLpgSQL_execstate *estate,
61246145
cast_expr= (Node*)expression_planner((Expr*)cast_expr);
61256146

61266147
/* Now copy the tree into cast_hash_context */
6127-
MemoryContextSwitchTo(cast_hash_context);
6148+
MemoryContextSwitchTo(estate->cast_hash_context);
61286149

61296150
cast_expr=copyObject(cast_expr);
61306151
}
61316152

61326153
MemoryContextSwitchTo(oldcontext);
61336154

61346155
/* Now we can fill in a hashtable entry. */
6135-
cast_entry= (plpgsql_CastHashEntry*)hash_search(cast_hash,
6156+
cast_entry= (plpgsql_CastHashEntry*)hash_search(estate->cast_hash,
61366157
(void*)&cast_key,
61376158
HASH_ENTER,&found);
61386159
Assert(!found);/* wasn't there a moment ago */
@@ -6154,7 +6175,9 @@ get_cast_hashentry(PLpgSQL_execstate *estate,
61546175
* executions. (We will leak some memory intra-transaction if that
61556176
* happens a lot, but we don't expect it to.) It's okay to update the
61566177
* hash table with the new tree because all plpgsql functions within a
6157-
* given transaction share the same simple_eval_estate.
6178+
* given transaction share the same simple_eval_estate. (Well, regular
6179+
* functions do; DO blocks have private simple_eval_estates, and private
6180+
* cast hash tables to go with them.)
61586181
*/
61596182
curlxid=MyProc->lxid;
61606183
if (cast_entry->cast_lxid!=curlxid||cast_entry->cast_in_use)

‎src/pl/plpgsql/src/plpgsql.h‎

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -796,6 +796,10 @@ typedef struct PLpgSQL_execstate
796796
/* EState to use for "simple" expression evaluation */
797797
EState*simple_eval_estate;
798798

799+
/* Lookup table to use for executing type casts */
800+
HTAB*cast_hash;
801+
MemoryContextcast_hash_context;
802+
799803
/* temporary state for results from evaluation of query or expr */
800804
SPITupleTable*eval_tuptable;
801805
uint32eval_processed;

‎src/test/regress/expected/plpgsql.out‎

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -4764,6 +4764,13 @@ commit;
47644764
drop function cast_invoker(integer);
47654765
drop function sql_to_date(integer) cascade;
47664766
NOTICE: drop cascades to cast from integer to date
4767+
-- Test handling of cast cache inside DO blocks
4768+
-- (to check the original crash case, this must be a cast not previously
4769+
-- used in this session)
4770+
begin;
4771+
do $$ declare x text[]; begin x := '{1.23, 4.56}'::numeric[]; end $$;
4772+
do $$ declare x text[]; begin x := '{1.23, 4.56}'::numeric[]; end $$;
4773+
end;
47674774
-- Test for consistent reporting of error context
47684775
create function fail() returns int language plpgsql as $$
47694776
begin

‎src/test/regress/sql/plpgsql.sql‎

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -3836,6 +3836,15 @@ commit;
38363836
dropfunction cast_invoker(integer);
38373837
dropfunction sql_to_date(integer) cascade;
38383838

3839+
-- Test handling of cast cache inside DO blocks
3840+
-- (to check the original crash case, this must be a cast not previously
3841+
-- used in this session)
3842+
3843+
begin;
3844+
do $$ declare xtext[];begin x :='{1.23, 4.56}'::numeric[]; end $$;
3845+
do $$ declare xtext[];begin x :='{1.23, 4.56}'::numeric[]; end $$;
3846+
end;
3847+
38393848
-- Test for consistent reporting of error context
38403849

38413850
createfunctionfail() returnsint language plpgsqlas $$

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