Fix unitialized variables

As complained by clang, reported by Andres Freund.  Brown paper bag bug
in ccc4c074994d.

Add some comments, too.

Backpatch to 9.5, like that one.

diff --git a/src/backend/access/brin/brin_pageops.c b/src/backend/access/brin/brin_pageops.c
index 875544e336c07eca7039fb74fc3edf1c783581b1..6a2fd474d9aa2c664e142fa5b1967da5a8202789 100644 (file)
--- a/src/backend/access/brin/brin_pageops.c
+++ b/src/backend/access/brin/brin_pageops.c
@@ -86,6 +86,7 @@ brin_doupdate(Relation idxrel, BlockNumber pagesPerRange,
    {
        LockBuffer(oldbuf, BUFFER_LOCK_EXCLUSIVE);
        newbuf = InvalidBuffer;
+       extended = false;
    }
    oldpage = BufferGetPage(oldbuf);
    oldlp = PageGetItemId(oldpage, oldoff);
@@ -335,9 +336,8 @@ brin_doinsert(Relation idxrel, BlockNumber pagesPerRange,
    brinRevmapExtend(revmap, heapBlk);
 
    /*
-    * Obtain a locked buffer to insert the new tuple.  Note
-    * brin_getinsertbuffer ensures there's enough space in the returned
-    * buffer.
+    * Acquire lock on buffer supplied by caller, if any.  If it doesn't have
+    * enough space, unpin it to obtain a new one below.
     */
    if (BufferIsValid(*buffer))
    {
@@ -354,12 +354,18 @@ brin_doinsert(Relation idxrel, BlockNumber pagesPerRange,
        }
    }
 
+   /*
+    * If we still don't have a usable buffer, have brin_getinsertbuffer
+    * obtain one for us.
+    */
    if (!BufferIsValid(*buffer))
    {
        *buffer = brin_getinsertbuffer(idxrel, InvalidBuffer, itemsz, &extended);
        Assert(BufferIsValid(*buffer));
        Assert(extended || br_page_get_freespace(BufferGetPage(*buffer)) >= itemsz);
    }
+   else
+       extended = false;
 
    /* Now obtain lock on revmap buffer */
    revmapbuf = brinLockRevmapPageForUpdate(revmap, heapBlk);
@@ -367,6 +373,7 @@ brin_doinsert(Relation idxrel, BlockNumber pagesPerRange,
    page = BufferGetPage(*buffer);
    blk = BufferGetBlockNumber(*buffer);
 
+   /* Execute the actual insertion */
    START_CRIT_SECTION();
    if (extended)
        brin_page_init(BufferGetPage(*buffer), BRIN_PAGETYPE_REGULAR);