Assert that we don't insert nulls into attnotnull catalog columns.

tglsfdc · tglsfdc · commit 43ef3c4c360a · 2020-07-21T12:38:08.000-04:00
The executor checks for this error, and so does the bootstrap catalog loader, but we never checked for it in retail catalog manipulations. The folly of that has now been exposed, so let's add assertions checking it. Checking in CatalogTupleInsert[WithInfo] and CatalogTupleUpdate[WithInfo] should be enough to cover this. Back-patch to v10; the aforesaid functions didn't exist before that, and it didn't seem worth adapting the patch to the oldest branches. But given the risk of JIT crashes, I think we certainly need this as far back as v11. Pre-v13, we have to explicitly exclude pg_subscription.subslotname and pg_subscription_rel.srsublsn from the checks, since they are mismarked. (Even if we change our mind about applying BKI_FORCE_NULL in the branch tips, it doesn't seem wise to have assertions that would fire in existing databases.) Discussion: https://postgr.es/m/298837.1595196283@sss.pgh.pa.us
diff --git a/doc/src/sgml/bki.sgml b/doc/src/sgml/bki.sgml
@@ -122,10 +122,7 @@
    if they are fixed-width and are not preceded by any nullable column.
    Where this rule is inadequate, you can force correct marking by using
    <literal>BKI_FORCE_NOT_NULL</literal>
-   and <literal>BKI_FORCE_NULL</literal> annotations as needed.  But note
-   that <literal>NOT NULL</literal> constraints are only enforced in the
-   executor, not against tuples that are generated by random C code,
-   so care is still needed when manually creating or updating catalog rows.
+   and <literal>BKI_FORCE_NULL</literal> annotations as needed.
   </para>
 
   <para>
diff --git a/src/backend/catalog/indexing.c b/src/backend/catalog/indexing.c
@@ -20,6 +20,8 @@
 #include "access/htup_details.h"
 #include "catalog/index.h"
 #include "catalog/indexing.h"
+#include "catalog/pg_subscription.h"
+#include "catalog/pg_subscription_rel.h"
 #include "executor/executor.h"
 #include "utils/rel.h"
 
@@ -167,6 +169,53 @@ CatalogIndexInsert(CatalogIndexState indstate, HeapTuple heapTuple)
 	ExecDropSingleTupleTableSlot(slot);
 }
 
+/*
+ * Subroutine to verify that catalog constraints are honored.
+ *
+ * Tuples inserted via CatalogTupleInsert/CatalogTupleUpdate are generally
+ * "hand made", so that it's possible that they fail to satisfy constraints
+ * that would be checked if they were being inserted by the executor.  That's
+ * a coding error, so we only bother to check for it in assert-enabled builds.
+ */
+#ifdef USE_ASSERT_CHECKING
+
+static void
+CatalogTupleCheckConstraints(Relation heapRel, HeapTuple tup)
+{
+	/*
+	 * Currently, the only constraints implemented for system catalogs are
+	 * attnotnull constraints.
+	 */
+	if (HeapTupleHasNulls(tup))
+	{
+		TupleDesc	tupdesc = RelationGetDescr(heapRel);
+		bits8	   *bp = tup->t_data->t_bits;
+
+		for (int attnum = 0; attnum < tupdesc->natts; attnum++)
+		{
+			Form_pg_attribute thisatt = TupleDescAttr(tupdesc, attnum);
+
+			/*
+			 * Through an embarrassing oversight, pre-v13 installations have
+			 * pg_subscription.subslotname and pg_subscription_rel.srsublsn
+			 * marked as attnotnull, which they should not be.  Ignore those
+			 * flags.
+			 */
+			Assert(!(thisatt->attnotnull && att_isnull(attnum, bp) &&
+					 !((thisatt->attrelid == SubscriptionRelationId &&
+						thisatt->attnum == Anum_pg_subscription_subslotname) ||
+					   (thisatt->attrelid == SubscriptionRelRelationId &&
+						thisatt->attnum == Anum_pg_subscription_rel_srsublsn))));
+		}
+	}
+}
+
+#else							/* !USE_ASSERT_CHECKING */
+
+#define CatalogTupleCheckConstraints(heapRel, tup)  ((void) 0)
+
+#endif							/* USE_ASSERT_CHECKING */
+
 /*
  * CatalogTupleInsert - do heap and indexing work for a new catalog tuple
  *
@@ -184,6 +233,8 @@ CatalogTupleInsert(Relation heapRel, HeapTuple tup)
 {
 	CatalogIndexState indstate;
 
+	CatalogTupleCheckConstraints(heapRel, tup);
+
 	indstate = CatalogOpenIndexes(heapRel);
 
 	simple_heap_insert(heapRel, tup);
@@ -204,6 +255,8 @@ void
 CatalogTupleInsertWithInfo(Relation heapRel, HeapTuple tup,
 						   CatalogIndexState indstate)
 {
+	CatalogTupleCheckConstraints(heapRel, tup);
+
 	simple_heap_insert(heapRel, tup);
 
 	CatalogIndexInsert(indstate, tup);
@@ -225,6 +278,8 @@ CatalogTupleUpdate(Relation heapRel, ItemPointer otid, HeapTuple tup)
 {
 	CatalogIndexState indstate;
 
+	CatalogTupleCheckConstraints(heapRel, tup);
+
 	indstate = CatalogOpenIndexes(heapRel);
 
 	simple_heap_update(heapRel, otid, tup);
@@ -245,6 +300,8 @@ void
 CatalogTupleUpdateWithInfo(Relation heapRel, ItemPointer otid, HeapTuple tup,
 						   CatalogIndexState indstate)
 {
+	CatalogTupleCheckConstraints(heapRel, tup);
+
 	simple_heap_update(heapRel, otid, tup);
 
 	CatalogIndexInsert(indstate, tup);
