Fix memory leak in repeated GIN index searches.

Commit d88976cfa1302e8d 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

diff --git a/src/backend/access/gin/ginget.c b/src/backend/access/gin/ginget.c
index 54b2db88a688c81b4da26faf89b89765119b9ffc..ee2eb63346801c4d2dafe8a9ab28685348872db0 100644 (file)
--- a/src/backend/access/gin/ginget.c
+++ b/src/backend/access/gin/ginget.c
@@ -302,6 +302,8 @@ restartScanEntry:
    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
index ac3a92b1981a372a04dc1799b9c96689554ba543..81e4a6ac6ae1388c5d5bfa1bf78d6c68f7dd0396 100644 (file)
--- 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;