Fix handling of non-upgraded B-tree metapages

857f9c36 bumps B-tree metapage version while upgrade is performed "on the fly"
when needed. However, some asserts fired when old version metapage was
cached to rel->rd_amcache. Despite new metadata fields are never used from
rel->rd_amcache, that needs to be fixed. This patch introduces metadata
upgrade during its caching, which fills unavailable fields with their default
values. contrib/pageinspect is also patched to handle non-upgraded metapages
in the same way.

Author: Alexander Korotkov

diff --git a/contrib/pageinspect/btreefuncs.c b/contrib/pageinspect/btreefuncs.c
index 5133653791952a8e93b35a202352d20c3aac864d..558a8c41f49c63e33e83f9e831168859fc1f84d0 100644 (file)
--- a/contrib/pageinspect/btreefuncs.c
+++ b/contrib/pageinspect/btreefuncs.c
@@ -555,8 +555,21 @@ bt_metap(PG_FUNCTION_ARGS)
        values[j++] = psprintf("%d", metad->btm_level);
        values[j++] = psprintf("%d", metad->btm_fastroot);
        values[j++] = psprintf("%d", metad->btm_fastlevel);
-       values[j++] = psprintf("%u", metad->btm_oldest_btpo_xact);
-       values[j++] = psprintf("%lf", metad->btm_last_cleanup_num_heap_tuples);
+
+       /*
+        * Get values of extended metadata if available, use default values
+        * otherwise.
+        */
+       if (metad->btm_version == BTREE_VERSION)
+       {
+               values[j++] = psprintf("%u", metad->btm_oldest_btpo_xact);
+               values[j++] = psprintf("%lf", metad->btm_last_cleanup_num_heap_tuples);
+       }
+       else
+       {
+               values[j++] = "0";
+               values[j++] = "-1";
+       }
 
        tuple = BuildTupleFromCStrings(TupleDescGetAttInMetadata(tupleDesc),
                                                                   values);

diff --git a/src/backend/access/nbtree/nbtpage.c b/src/backend/access/nbtree/nbtpage.c
index c98603bbf8f325e997c3e41e5b4a4ab632fbebd3..019fe48cb6ebc0398f8de3a19547418972378ba5 100644 (file)
--- a/src/backend/access/nbtree/nbtpage.c
+++ b/src/backend/access/nbtree/nbtpage.c
@@ -33,6 +33,7 @@
 #include "storage/predicate.h"
 #include "utils/snapmgr.h"
 
+static void _bt_cachemetadata(Relation rel, BTMetaPageData *metad);
 static bool _bt_mark_page_halfdead(Relation rel, Buffer buf, BTStack stack);
 static bool _bt_unlink_halfdead_page(Relation rel, Buffer leafbuf,
                                                 bool *rightsib_empty);
@@ -105,6 +106,44 @@ _bt_upgrademetapage(Page page)
                ((char *) metad + sizeof(BTMetaPageData)) - (char *) page;
 }
 
+/*
+ * Cache metadata from meta page to rel->rd_amcache.
+ */
+static void
+_bt_cachemetadata(Relation rel, BTMetaPageData *metad)
+{
+       /* We assume rel->rd_amcache was already freed by caller */
+       Assert(rel->rd_amcache == NULL);
+       rel->rd_amcache = MemoryContextAlloc(rel->rd_indexcxt,
+                                                                                sizeof(BTMetaPageData));
+
+       /*
+        * Meta page should be of supported version (should be already checked by
+        * caller).
+        */
+       Assert(metad->btm_version >= BTREE_MIN_VERSION &&
+                  metad->btm_version <= BTREE_VERSION);
+
+       if (metad->btm_version == BTREE_VERSION)
+       {
+               /* Last version of meta-data, no need to upgrade */
+               memcpy(rel->rd_amcache, metad, sizeof(BTMetaPageData));
+       }
+       else
+       {
+               BTMetaPageData *cached_metad = (BTMetaPageData *) rel->rd_amcache;
+
+               /*
+                * Upgrade meta-data: copy available information from meta-page and
+                * fill new fields with default values.
+                */
+               memcpy(rel->rd_amcache, metad, offsetof(BTMetaPageData, btm_oldest_btpo_xact));
+               cached_metad->btm_version = BTREE_VERSION;
+               cached_metad->btm_oldest_btpo_xact = InvalidTransactionId;
+               cached_metad->btm_last_cleanup_num_heap_tuples = -1.0;
+       }
+}
+
 /*
  *     _bt_update_meta_cleanup_info() -- Update cleanup-related information in
  *                                                                       the metapage.
@@ -403,9 +442,7 @@ _bt_getroot(Relation rel, int access)
                /*
                 * Cache the metapage data for next time
                 */
-               rel->rd_amcache = MemoryContextAlloc(rel->rd_indexcxt,
-                                                                                        sizeof(BTMetaPageData));
-               memcpy(rel->rd_amcache, metad, sizeof(BTMetaPageData));
+               _bt_cachemetadata(rel, metad);
 
                /*
                 * We are done with the metapage; arrange to release it via first
@@ -604,9 +641,7 @@ _bt_getrootheight(Relation rel)
                /*
                 * Cache the metapage data for next time
                 */
-               rel->rd_amcache = MemoryContextAlloc(rel->rd_indexcxt,
-                                                                                        sizeof(BTMetaPageData));
-               memcpy(rel->rd_amcache, metad, sizeof(BTMetaPageData));
+               _bt_cachemetadata(rel, metad);
 
                _bt_relbuf(rel, metabuf);
        }