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Avoid holding a directory FD open across assorted SRF calls.

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This extends the fixes made in commit 085b6b667 to other SRFs with the
same bug, namely pg_logdir_ls(), pgrowlocks(), pg_timezone_names(),
pg_ls_dir(), and pg_tablespace_databases().

Also adjust various comments and documentation to warn against
expecting to clean up resources during a ValuePerCall SRF's final
call.

Back-patch to all supported branches, since these functions were
all born broken.

Justin Pryzby, with cosmetic tweaks by me

Discussion: https://postgr.es/m/20200308173103.GC1357@telsasoft.com
This commit is contained in:
Tom Lane
2020-03-16 21:05:29 -04:00
parent 5c3a70020a
commit da254148f4
8 changed files with 342 additions and 326 deletions
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112
contrib/pgrowlocks/pgrowlocks.c
View File

@ -50,13 +50,6 @@ PG_FUNCTION_INFO_V1(pgrowlocks);
#define NCHARS 32
typedef struct
{
Relation rel;
HeapScanDesc scan;
int ncolumns;
} MyData;
#define Atnum_tid 0
#define Atnum_xmax 1
#define Atnum_ismulti 2
@ -67,59 +60,62 @@ typedef struct
Datum
pgrowlocks(PG_FUNCTION_ARGS)
{
FuncCallContext *funcctx;
text *relname = PG_GETARG_TEXT_PP(0);
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
bool randomAccess;
TupleDesc tupdesc;
Tuplestorestate *tupstore;
AttInMetadata *attinmeta;
Relation rel;
RangeVar *relrv;
HeapScanDesc scan;
HeapTuple tuple;
TupleDesc tupdesc;
AttInMetadata *attinmeta;
Datum result;
MyData *mydata;
Relation rel;
MemoryContext oldcontext;
AclResult aclresult;
char **values;
if (SRF_IS_FIRSTCALL())
{
text *relname;
RangeVar *relrv;
MemoryContext oldcontext;
AclResult aclresult;
/* check to see if caller supports us returning a tuplestore */
if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("set-valued function called in context that cannot accept a set")));
if (!(rsinfo->allowedModes & SFRM_Materialize))
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("materialize mode required, but it is not allowed in this context")));
funcctx = SRF_FIRSTCALL_INIT();
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
/* The tupdesc and tuplestore must be created in ecxt_per_query_memory */
oldcontext = MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
/* Build a tuple descriptor for our result type */
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
attinmeta = TupleDescGetAttInMetadata(tupdesc);
funcctx->attinmeta = attinmeta;
randomAccess = (rsinfo->allowedModes & SFRM_Materialize_Random) != 0;
tupstore = tuplestore_begin_heap(randomAccess, false, work_mem);
rsinfo->returnMode = SFRM_Materialize;
rsinfo->setResult = tupstore;
rsinfo->setDesc = tupdesc;
relname = PG_GETARG_TEXT_P(0);
relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
rel = heap_openrv(relrv, AccessShareLock);
MemoryContextSwitchTo(oldcontext);
/* check permissions: must have SELECT on table */
aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
ACL_SELECT);
if (aclresult != ACLCHECK_OK)
aclcheck_error(aclresult, ACL_KIND_CLASS,
RelationGetRelationName(rel));
/* Access the table */
relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
rel = heap_openrv(relrv, AccessShareLock);
scan = heap_beginscan(rel, GetActiveSnapshot(), 0, NULL);
mydata = palloc(sizeof(*mydata));
mydata->rel = rel;
mydata->scan = scan;
mydata->ncolumns = tupdesc->natts;
funcctx->user_fctx = mydata;
/* check permissions: must have SELECT on table */
aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
ACL_SELECT);
if (aclresult != ACLCHECK_OK)
aclcheck_error(aclresult, ACL_KIND_CLASS,
RelationGetRelationName(rel));
MemoryContextSwitchTo(oldcontext);
}
/* Scan the relation */
scan = heap_beginscan(rel, GetActiveSnapshot(), 0, NULL);
funcctx = SRF_PERCALL_SETUP();
attinmeta = funcctx->attinmeta;
mydata = (MyData *) funcctx->user_fctx;
scan = mydata->scan;
attinmeta = TupleDescGetAttInMetadata(tupdesc);
values = (char **) palloc(tupdesc->natts * sizeof(char *));
/* scan the relation */
while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
{
HTSU_Result htsu;
@ -140,10 +136,6 @@ pgrowlocks(PG_FUNCTION_ARGS)
*/
if (htsu == HeapTupleBeingUpdated)
{
char **values;
values = (char **) palloc(mydata->ncolumns * sizeof(char *));
values[Atnum_tid] = (char *) DirectFunctionCall1(tidout,
PointerGetDatum(&tuple->t_self));
@ -268,16 +260,7 @@ pgrowlocks(PG_FUNCTION_ARGS)
/* build a tuple */
tuple = BuildTupleFromCStrings(attinmeta, values);
/* make the tuple into a datum */
result = HeapTupleGetDatum(tuple);
/*
* no need to pfree what we allocated; it's on a short-lived
* memory context anyway
*/
SRF_RETURN_NEXT(funcctx, result);
tuplestore_puttuple(tupstore, tuple);
}
else
{
@ -286,7 +269,6 @@ pgrowlocks(PG_FUNCTION_ARGS)
}
heap_endscan(scan);
heap_close(mydata->rel, AccessShareLock);
SRF_RETURN_DONE(funcctx);
heap_close(rel, AccessShareLock);
return (Datum) 0;
}