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Make visibilitymap_set() return previous state of vmbits
authorMelanie Plageman <melanieplageman@gmail.com>
Tue, 17 Dec 2024 19:13:18 +0000 (14:13 -0500)
committerMelanie Plageman <melanieplageman@gmail.com>
Tue, 17 Dec 2024 19:19:03 +0000 (14:19 -0500)
It can be useful to know the state of a relation page's VM bits before
visibilitymap_set(). visibilitymap_set() has the old value on hand, so
returning it is simple. This commit does not use visibilitymap_set()'s
new return value.

Author: Melanie Plageman
Reviewed-by: Masahiko Sawada, Andres Freund, Nitin Jadhav, Bilal Yavuz
Discussion: https://postgr.es/m/flat/CAAKRu_ZQe26xdvAqo4weHLR%3DivQ8J4xrSfDDD8uXnh-O-6P6Lg%40mail.gmail.com#6d8d2b4219394f774889509bf3bdc13d,
https://postgr.es/m/ctdjzroezaxmiyah3gwbwm67defsrwj2b5fpfs4ku6msfpxeia%40mwjyqlhwr2wu

src/backend/access/heap/visibilitymap.c patch | blob | blame | history
src/include/access/visibilitymap.h patch | blob | blame | history

diff --git a/src/backend/access/heap/visibilitymap.c b/src/backend/access/heap/visibilitymap.c
index 8b24e7bc33cf6153fffd88a65e2e4c2b00321258..79b79d5982eb6860384abc4baa13c5041d547c03 100644 (file)
--- a/src/backend/access/heap/visibilitymap.c
+++ b/src/backend/access/heap/visibilitymap.c
@@ -239,8 +239,10 @@ visibilitymap_pin_ok(BlockNumber heapBlk, Buffer vmbuf)
  * You must pass a buffer containing the correct map page to this function.
  * Call visibilitymap_pin first to pin the right one. This function doesn't do
  * any I/O.
+ *
+ * Returns the state of the page's VM bits before setting flags.
  */
-void
+uint8
 visibilitymap_set(Relation rel, BlockNumber heapBlk, Buffer heapBuf,
                  XLogRecPtr recptr, Buffer vmBuf, TransactionId cutoff_xid,
                  uint8 flags)
@@ -250,6 +252,7 @@ visibilitymap_set(Relation rel, BlockNumber heapBlk, Buffer heapBuf,
    uint8       mapOffset = HEAPBLK_TO_OFFSET(heapBlk);
    Page        page;
    uint8      *map;
+   uint8       status;
 
 #ifdef TRACE_VISIBILITYMAP
    elog(DEBUG1, "vm_set %s %d", RelationGetRelationName(rel), heapBlk);
@@ -274,7 +277,8 @@ visibilitymap_set(Relation rel, BlockNumber heapBlk, Buffer heapBuf,
    map = (uint8 *) PageGetContents(page);
    LockBuffer(vmBuf, BUFFER_LOCK_EXCLUSIVE);
 
-   if (flags != (map[mapByte] >> mapOffset & VISIBILITYMAP_VALID_BITS))
+   status = (map[mapByte] >> mapOffset) & VISIBILITYMAP_VALID_BITS;
+   if (flags != status)
    {
        START_CRIT_SECTION();
 
@@ -311,6 +315,7 @@ visibilitymap_set(Relation rel, BlockNumber heapBlk, Buffer heapBuf,
    }
 
    LockBuffer(vmBuf, BUFFER_LOCK_UNLOCK);
+   return status;
 }
 
 /*
diff --git a/src/include/access/visibilitymap.h b/src/include/access/visibilitymap.h
index 1a4d467e6f02fce0f857c22f586f6e3207233518..f7779a0fe19a5a8d847a1a0afbaeaf903ca5c802 100644 (file)
--- a/src/include/access/visibilitymap.h
+++ b/src/include/access/visibilitymap.h
@@ -31,9 +31,12 @@ extern bool visibilitymap_clear(Relation rel, BlockNumber heapBlk,
 extern void visibilitymap_pin(Relation rel, BlockNumber heapBlk,
                              Buffer *vmbuf);
 extern bool visibilitymap_pin_ok(BlockNumber heapBlk, Buffer vmbuf);
-extern void visibilitymap_set(Relation rel, BlockNumber heapBlk, Buffer heapBuf,
-                             XLogRecPtr recptr, Buffer vmBuf, TransactionId cutoff_xid,
-                             uint8 flags);
+extern uint8 visibilitymap_set(Relation rel,
+                              BlockNumber heapBlk, Buffer heapBuf,
+                              XLogRecPtr recptr,
+                              Buffer vmBuf,
+                              TransactionId cutoff_xid,
+                              uint8 flags);
 extern uint8 visibilitymap_get_status(Relation rel, BlockNumber heapBlk, Buffer *vmbuf);
 extern void visibilitymap_count(Relation rel, BlockNumber *all_visible, BlockNumber *all_frozen);
 extern BlockNumber visibilitymap_prepare_truncate(Relation rel,
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