Revert "Prevent incorrect updates of pg_index while reindexing pg_index itself."

This reverts commit 8835284e0d903156632f76eea941cf5c592717ec of 2011-04-15.
There's a better way to do it, which will follow shortly.

diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 79b96a07d8d052638c586258ae6c88ffde6c54b0..487dbbf24d247251d3078839009687f7c96af7bc 100644 (file)
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -1423,13 +1423,6 @@ index_build(Relation heapRelation,
        HeapTuple   indexTuple;
        Form_pg_index indexForm;
 
-       /*
-        * Broken HOT chains should not get reported in system catalogs; in
-        * particular it would be quite dangerous to try to modify the index's
-        * pg_index entry if we are reindexing pg_index itself.
-        */
-       Assert(!IsSystemRelation(heapRelation));
-
        pg_index = heap_open(IndexRelationId, RowExclusiveLock);
 
        indexTuple = SearchSysCacheCopy(INDEXRELID,
@@ -1489,13 +1482,7 @@ index_build(Relation heapRelation,
  * A side effect is to set indexInfo->ii_BrokenHotChain to true if we detect
  * any potentially broken HOT chains.  Currently, we set this if there are
  * any RECENTLY_DEAD entries in a HOT chain, without trying very hard to
- * detect whether they're really incompatible with the chain tip.  However,
- * we do not ever set ii_BrokenHotChain true when the relation is a system
- * catalog.  This is to avoid problematic behavior when reindexing pg_index
- * itself: we can't safely change the index's indcheckxmin field when we're
- * partway through such an operation.  It should be okay since the set of
- * indexes on a system catalog ought not change during concurrent operations,
- * so that no HOT chain in it could ever become broken.
+ * detect whether they're really incompatible with the chain tip.
  */
 double
 IndexBuildHeapScan(Relation heapRelation,
@@ -1505,7 +1492,6 @@ IndexBuildHeapScan(Relation heapRelation,
                   IndexBuildCallback callback,
                   void *callback_state)
 {
-   bool        is_system_catalog;
    HeapScanDesc scan;
    HeapTuple   heapTuple;
    Datum       values[INDEX_MAX_KEYS];
@@ -1525,9 +1511,6 @@ IndexBuildHeapScan(Relation heapRelation,
     */
    Assert(OidIsValid(indexRelation->rd_rel->relam));
 
-   /* Remember if it's a system catalog */
-   is_system_catalog = IsSystemRelation(heapRelation);
-
    /*
     * Need an EState for evaluation of index expressions and partial-index
     * predicates.  Also a slot to hold the current tuple.
@@ -1666,8 +1649,7 @@ IndexBuildHeapScan(Relation heapRelation,
                    {
                        indexIt = false;
                        /* mark the index as unsafe for old snapshots */
-                       if (!is_system_catalog)
-                           indexInfo->ii_BrokenHotChain = true;
+                       indexInfo->ii_BrokenHotChain = true;
                    }
                    else if (indexInfo->ii_BrokenHotChain)
                        indexIt = false;
@@ -1756,8 +1738,7 @@ IndexBuildHeapScan(Relation heapRelation,
                    {
                        indexIt = false;
                        /* mark the index as unsafe for old snapshots */
-                       if (!is_system_catalog)
-                           indexInfo->ii_BrokenHotChain = true;
+                       indexInfo->ii_BrokenHotChain = true;
                    }
                    else if (indexInfo->ii_BrokenHotChain)
                        indexIt = false;
@@ -2371,35 +2352,27 @@ reindex_index(Oid indexId)
     * We can also reset indcheckxmin, because we have now done a
     * non-concurrent index build, *except* in the case where index_build
     * found some still-broken HOT chains.
-    *
-    * When reindexing a system catalog, don't do any of this --- it would be
-    * particularly risky to try to modify pg_index while we are reindexing
-    * pg_index itself.  We don't support CREATE INDEX CONCURRENTLY on system
-    * catalogs anyway, and they should never have indcheckxmin set either.
     */
-   if (!IsSystemRelation(heapRelation))
-   {
-       pg_index = heap_open(IndexRelationId, RowExclusiveLock);
+   pg_index = heap_open(IndexRelationId, RowExclusiveLock);
 
-       indexTuple = SearchSysCacheCopy(INDEXRELID,
-                                       ObjectIdGetDatum(indexId),
-                                       0, 0, 0);
-       if (!HeapTupleIsValid(indexTuple))
-           elog(ERROR, "cache lookup failed for index %u", indexId);
-       indexForm = (Form_pg_index) GETSTRUCT(indexTuple);
+   indexTuple = SearchSysCacheCopy(INDEXRELID,
+                                   ObjectIdGetDatum(indexId),
+                                   0, 0, 0);
+   if (!HeapTupleIsValid(indexTuple))
+       elog(ERROR, "cache lookup failed for index %u", indexId);
+   indexForm = (Form_pg_index) GETSTRUCT(indexTuple);
 
-       if (!indexForm->indisvalid || !indexForm->indisready ||
-           (indexForm->indcheckxmin && !indexInfo->ii_BrokenHotChain))
-       {
-           indexForm->indisvalid = true;
-           indexForm->indisready = true;
-           if (!indexInfo->ii_BrokenHotChain)
-               indexForm->indcheckxmin = false;
-           simple_heap_update(pg_index, &indexTuple->t_self, indexTuple);
-           CatalogUpdateIndexes(pg_index, indexTuple);
-       }
-       heap_close(pg_index, RowExclusiveLock);
+   if (!indexForm->indisvalid || !indexForm->indisready ||
+       (indexForm->indcheckxmin && !indexInfo->ii_BrokenHotChain))
+   {
+       indexForm->indisvalid = true;
+       indexForm->indisready = true;
+       if (!indexInfo->ii_BrokenHotChain)
+           indexForm->indcheckxmin = false;
+       simple_heap_update(pg_index, &indexTuple->t_self, indexTuple);
+       CatalogUpdateIndexes(pg_index, indexTuple);
    }
+   heap_close(pg_index, RowExclusiveLock);
 
    /* Close rels, but keep locks */
    index_close(iRel, NoLock);