compact_fsm_storage() does need to handle the case where a relation's

FSM data has to be both moved down and compressed.  Per report from
Dror Matalon.

diff --git a/src/backend/storage/freespace/freespace.c b/src/backend/storage/freespace/freespace.c
index 51f8e4ea5da87f1683819cd4971fbc286352e45c..b5e1a53b35eea118cd00ae819dfd78b2cb95a656 100644 (file)
--- a/src/backend/storage/freespace/freespace.c
+++ b/src/backend/storage/freespace/freespace.c
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/storage/freespace/freespace.c,v 1.23 2003/09/29 00:05:25 petere Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/storage/freespace/freespace.c,v 1.24 2003/10/29 17:36:57 tgl Exp $
  *
  *
  * NOTES:
@@ -1432,19 +1432,29 @@ compact_fsm_storage(void)
 
        /*
         * It's possible that we have to move data down, not up, if the
-        * allocations of previous rels expanded.  This should mean that
+        * allocations of previous rels expanded.  This normally means that
         * our allocation expanded too (or at least got no worse), and
-        * ditto for later rels.  So there should be room --- but we might
-        * have to push down following rels to make it.  We don't want to
-        * do the push more than once, so pack everything against the end
-        * of the arena if so.
+        * ditto for later rels.  So there should be room to move all our
+        * data down without dropping any --- but we might have to push down
+        * following rels to acquire the room.  We don't want to do the push
+        * more than once, so pack everything against the end of the arena
+        * if so.
+        *
+        * In corner cases where roundoff has affected our allocation, it's
+        * possible that we have to move down and compress our data too.
+        * Since this case is extremely infrequent, we do not try to be smart
+        * about it --- we just drop pages from the end of the rel's data.
         */
        if (newChunkIndex > oldChunkIndex)
        {
            int         limitChunkIndex;
 
            if (newAllocPages < fsmrel->storedPages)
-               elog(PANIC, "can't juggle and compress too");
+           {
+               /* move and compress --- just drop excess pages */
+               fsmrel->storedPages = newAllocPages;
+               curChunks = fsm_current_chunks(fsmrel);
+           }
            if (fsmrel->nextPhysical != NULL)
                limitChunkIndex = fsmrel->nextPhysical->firstChunk;
            else
@@ -1459,7 +1469,7 @@ compact_fsm_storage(void)
                else
                    limitChunkIndex = FreeSpaceMap->totalChunks;
                if (newChunkIndex + curChunks > limitChunkIndex)
-                   elog(PANIC, "insufficient room");
+                   elog(PANIC, "insufficient room in FSM");
            }
            memmove(newLocation, oldLocation, curChunks * CHUNKBYTES);
        }
@@ -1535,7 +1545,7 @@ push_fsm_rels_after(FSMRelation *afterRel)
        if (newChunkIndex < oldChunkIndex)
        {
            /* trouble... */
-           elog(PANIC, "out of room");
+           elog(PANIC, "insufficient room in FSM");
        }
        else if (newChunkIndex > oldChunkIndex)
        {