Clean up data conversion short-lived memory context.

dblink uses a short-lived data conversion memory context. However it
was not deleted when no longer needed, leading to a noticeable memory
leak under some circumstances. Plug the hole, along with minor
refactoring. Backpatch to 9.2 where the leak was introduced.

Report and initial patch by MauMau. Reviewed/modified slightly by
Tom Lane and me.

diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c
index a81853fa9118170f7773363c76afb07afe633f19..d77b3ee34ba2e7b28558636ccbd1ba1f2bcdb1df 100644 (file)
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -977,6 +977,13 @@ materializeQueryResult(FunctionCallInfo fcinfo,
 
        PG_TRY();
        {
+               /* Create short-lived memory context for data conversions */
+               sinfo.tmpcontext = AllocSetContextCreate(CurrentMemoryContext,
+                                                                                                "dblink temporary context",
+                                                                                                ALLOCSET_DEFAULT_MINSIZE,
+                                                                                                ALLOCSET_DEFAULT_INITSIZE,
+                                                                                                ALLOCSET_DEFAULT_MAXSIZE);
+
                /* execute query, collecting any tuples into the tuplestore */
                res = storeQueryResult(&sinfo, conn, sql);
 
@@ -1041,6 +1048,12 @@ materializeQueryResult(FunctionCallInfo fcinfo,
                        PQclear(res);
                        res = NULL;
                }
+
+               /* clean up data conversion short-lived memory context */
+               if (sinfo.tmpcontext != NULL)
+                       MemoryContextDelete(sinfo.tmpcontext);
+               sinfo.tmpcontext = NULL;
+
                PQclear(sinfo.last_res);
                sinfo.last_res = NULL;
                PQclear(sinfo.cur_res);
@@ -1204,15 +1217,6 @@ storeRow(storeInfo *sinfo, PGresult *res, bool first)
                if (sinfo->cstrs)
                        pfree(sinfo->cstrs);
                sinfo->cstrs = (char **) palloc(nfields * sizeof(char *));
-
-               /* Create short-lived memory context for data conversions */
-               if (!sinfo->tmpcontext)
-                       sinfo->tmpcontext =
-                               AllocSetContextCreate(CurrentMemoryContext,
-                                                                         "dblink temporary context",
-                                                                         ALLOCSET_DEFAULT_MINSIZE,
-                                                                         ALLOCSET_DEFAULT_INITSIZE,
-                                                                         ALLOCSET_DEFAULT_MAXSIZE);
        }
 
        /* Should have a single-row result if we get here */