pageinspect: Fix relcache leak in gist_page_items().

The gist_page_items() function opened the index relation on first call and
closed it on the last call. But there's no guarantee that the function is
run to completion, leading to a relcache leak and warning at the end of
the transaction. To fix, refactor the function to return all the rows in
one call, as a tuplestore.

Reported-by: Tom Lane
Discussion: https://www.postgresql.org/message-id/234863.1610916631%40sss.pgh.pa.us

diff --git a/contrib/pageinspect/gistfuncs.c b/contrib/pageinspect/gistfuncs.c
index 146b2e91b6011023251939cfda1b0bbf56c89263..6e1ea04b346ad4b246987f48187e1ca77b501edf 100644 (file)
--- a/contrib/pageinspect/gistfuncs.c
+++ b/contrib/pageinspect/gistfuncs.c
@@ -92,65 +92,56 @@ gist_page_opaque_info(PG_FUNCTION_ARGS)
    return HeapTupleGetDatum(resultTuple);
 }
 
-typedef struct gist_page_items_state
-{
-   Page        page;
-   TupleDesc   tupd;
-   OffsetNumber offset;
-   Relation    rel;
-} gist_page_items_state;
-
 Datum
 gist_page_items_bytea(PG_FUNCTION_ARGS)
 {
    bytea      *raw_page = PG_GETARG_BYTEA_P(0);
-   FuncCallContext *fctx;
-   gist_page_items_state *inter_call_data;
+   ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+   bool        randomAccess;
+   TupleDesc   tupdesc;
+   Tuplestorestate *tupstore;
+   MemoryContext oldcontext;
+   Page        page;
+   OffsetNumber offset;
 
    if (!superuser())
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("must be superuser to use raw page functions")));
 
-   if (SRF_IS_FIRSTCALL())
-   {
-       TupleDesc   tupdesc;
-       MemoryContext mctx;
-       Page        page;
-
-       fctx = SRF_FIRSTCALL_INIT();
-       mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);
-
-       page = get_page_from_raw(raw_page);
-
-       inter_call_data = palloc(sizeof(gist_page_items_state));
+   /* 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")));
 
-       /* 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");
+   /* The tupdesc and tuplestore must be created in ecxt_per_query_memory */
+   oldcontext = MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
 
-       if (GistPageIsDeleted(page))
-           elog(NOTICE, "page is deleted");
+   if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+       elog(ERROR, "return type must be a row type");
 
-       inter_call_data->page = page;
-       inter_call_data->tupd = tupdesc;
-       inter_call_data->offset = FirstOffsetNumber;
+   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;
 
-       fctx->max_calls = PageGetMaxOffsetNumber(page);
-       fctx->user_fctx = inter_call_data;
+   MemoryContextSwitchTo(oldcontext);
 
-       MemoryContextSwitchTo(mctx);
-   }
+   page = get_page_from_raw(raw_page);
 
-   fctx = SRF_PERCALL_SETUP();
-   inter_call_data = fctx->user_fctx;
+   if (GistPageIsDeleted(page))
+       elog(NOTICE, "page is deleted");
 
-   if (fctx->call_cntr < fctx->max_calls)
+   for (offset = FirstOffsetNumber;
+        offset <= PageGetMaxOffsetNumber(page);
+        offset++)
    {
-       Page        page = inter_call_data->page;
-       OffsetNumber offset = inter_call_data->offset;
-       HeapTuple   resultTuple;
-       Datum       result;
        Datum       values[4];
        bool        nulls[4];
        ItemId      id;
@@ -177,15 +168,10 @@ gist_page_items_bytea(PG_FUNCTION_ARGS)
        memcpy(VARDATA(tuple_bytea), itup, tuple_len);
        values[3] = PointerGetDatum(tuple_bytea);
 
-       /* Build and return the result tuple. */
-       resultTuple = heap_form_tuple(inter_call_data->tupd, values, nulls);
-       result = HeapTupleGetDatum(resultTuple);
-
-       inter_call_data->offset++;
-       SRF_RETURN_NEXT(fctx, result);
+       tuplestore_putvalues(tupstore, tupdesc, values, nulls);
    }
 
-   SRF_RETURN_DONE(fctx);
+   return (Datum) 0;
 }
 
 Datum
@@ -193,58 +179,56 @@ gist_page_items(PG_FUNCTION_ARGS)
 {
    bytea      *raw_page = PG_GETARG_BYTEA_P(0);
    Oid         indexRelid = PG_GETARG_OID(1);
-   FuncCallContext *fctx;
-   gist_page_items_state *inter_call_data;
+   ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+   bool        randomAccess;
+   Relation    indexRel;
+   TupleDesc   tupdesc;
+   Tuplestorestate *tupstore;
+   MemoryContext oldcontext;
+   Page        page;
+   OffsetNumber offset;
 
    if (!superuser())
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("must be superuser to use raw page functions")));
 
-   if (SRF_IS_FIRSTCALL())
-   {
-       Relation    indexRel;
-       TupleDesc   tupdesc;
-       MemoryContext mctx;
-       Page        page;
-
-       fctx = SRF_FIRSTCALL_INIT();
-       mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);
-
-       page = get_page_from_raw(raw_page);
-
-       inter_call_data = palloc(sizeof(gist_page_items_state));
+   /* 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")));
 
-       /* Open the relation */
-       indexRel = index_open(indexRelid, AccessShareLock);
+   /* 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");
 
-       if (GistPageIsDeleted(page))
-           elog(NOTICE, "page is deleted");
+   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;
 
-       inter_call_data->page = page;
-       inter_call_data->tupd = tupdesc;
-       inter_call_data->offset = FirstOffsetNumber;
-       inter_call_data->rel = indexRel;
+   MemoryContextSwitchTo(oldcontext);
 
-       fctx->max_calls = PageGetMaxOffsetNumber(page);
-       fctx->user_fctx = inter_call_data;
+   /* Open the relation */
+   indexRel = index_open(indexRelid, AccessShareLock);
 
-       MemoryContextSwitchTo(mctx);
-   }
+   page = get_page_from_raw(raw_page);
 
-   fctx = SRF_PERCALL_SETUP();
-   inter_call_data = fctx->user_fctx;
+   if (GistPageIsDeleted(page))
+       elog(NOTICE, "page is deleted");
 
-   if (fctx->call_cntr < fctx->max_calls)
+   for (offset = FirstOffsetNumber;
+        offset <= PageGetMaxOffsetNumber(page);
+        offset++)
    {
-       Page        page = inter_call_data->page;
-       OffsetNumber offset = inter_call_data->offset;
-       HeapTuple   resultTuple;
-       Datum       result;
        Datum       values[4];
        bool        nulls[4];
        ItemId      id;
@@ -260,11 +244,10 @@ gist_page_items(PG_FUNCTION_ARGS)
 
        itup = (IndexTuple) PageGetItem(page, id);
 
-       index_deform_tuple(itup, RelationGetDescr(inter_call_data->rel),
+       index_deform_tuple(itup, RelationGetDescr(indexRel),
                           itup_values, itup_isnull);
 
-       key_desc = BuildIndexValueDescription(inter_call_data->rel, itup_values,
-                                             itup_isnull);
+       key_desc = BuildIndexValueDescription(indexRel, itup_values, itup_isnull);
 
        memset(nulls, 0, sizeof(nulls));
 
@@ -273,15 +256,10 @@ gist_page_items(PG_FUNCTION_ARGS)
        values[2] = Int32GetDatum((int) IndexTupleSize(itup));
        values[3] = CStringGetTextDatum(key_desc);
 
-       /* Build and return the result tuple. */
-       resultTuple = heap_form_tuple(inter_call_data->tupd, values, nulls);
-       result = HeapTupleGetDatum(resultTuple);
-
-       inter_call_data->offset++;
-       SRF_RETURN_NEXT(fctx, result);
+       tuplestore_putvalues(tupstore, tupdesc, values, nulls);
    }
 
-   relation_close(inter_call_data->rel, AccessShareLock);
+   relation_close(indexRel, AccessShareLock);
 
-   SRF_RETURN_DONE(fctx);
+   return (Datum) 0;
 }