Fix memory leak in repeated GIN index searches.

tglsfdc · tglsfdc · commit aa9c4e71cecc · 2016-03-13T16:44:10.000-04:00
Commit d88976c removed this code from ginFreeScanKeys(): - if (entry->list) - pfree(entry->list); evidently in the belief that that ItemPointer array is allocated in the keyCtx and so would be reclaimed by the following MemoryContextReset. Unfortunately, it isn't and it won't. It'd likely be a good idea for that to become so, but as a simple and back-patchable fix in the meantime, restore this code to ginFreeScanKeys(). Also, add a similar pfree to where startScanEntry() is about to zero out entry->list. I am not sure if there are any code paths where this change prevents a leak today, but it seems like cheap future-proofing. In passing, make the initial allocation of so->entries[] use palloc not palloc0. The code doesn't depend on unused entries being zero; if it did, the array-enlargement code in ginFillScanEntry() would be wrong. So using palloc0 initially can only serve to confuse readers about what the invariant is. Per report from Felipe de Jesús Molina Bravo, via Jaime Casanova in <CAJGNTeMR1ndMU2Thpr8GPDUfiHTV7idELJRFusA5UXUGY1y-eA@mail.gmail.com>
diff --git a/src/backend/access/gin/ginget.c b/src/backend/access/gin/ginget.c
@@ -302,6 +302,8 @@ startScanEntry(GinState *ginstate, GinScanEntry entry)
 	entry->buffer = InvalidBuffer;
 	ItemPointerSetMin(&entry->curItem);
 	entry->offset = InvalidOffsetNumber;
+	if (entry->list)
+		pfree(entry->list);
 	entry->list = NULL;
 	entry->nlist = 0;
 	entry->matchBitmap = NULL;
diff --git a/src/backend/access/gin/ginscan.c b/src/backend/access/gin/ginscan.c
@@ -249,6 +249,8 @@ ginFreeScanKeys(GinScanOpaque so)
 
 		if (entry->buffer != InvalidBuffer)
 			ReleaseBuffer(entry->buffer);
+		if (entry->list)
+			pfree(entry->list);
 		if (entry->matchIterator)
 			tbm_end_iterate(entry->matchIterator);
 		if (entry->matchBitmap)
@@ -288,7 +290,7 @@ ginNewScanKey(IndexScanDesc scan)
 	so->totalentries = 0;
 	so->allocentries = 32;
 	so->entries = (GinScanEntry *)
-		palloc0(so->allocentries * sizeof(GinScanEntry));
+		palloc(so->allocentries * sizeof(GinScanEntry));
 
 	so->isVoidRes = false;
 
