Ensure an index that uses a whole-row Var still depends on its table.

We failed to record any dependency on the underlying table for an index
declared like "create index i on t (foo(t.*))".  This would create trouble
if the table were dropped without previously dropping the index.  To fix,
simplify some overly-cute code in index_create(), accepting the possibility
that sometimes the whole-table dependency will be redundant.  Also document
this hazard in dependency.c.  Per report from Kevin Grittner.

In passing, prevent a core dump in pg_get_indexdef() if the index's table
can't be found.  I came across this while experimenting with Kevin's
example.  Not sure it's a real issue when the catalogs aren't corrupt, but
might as well be cautious.

Back-patch to all supported versions.

3 files changed, 40 insertions, 14 deletions

diff --git a/src/backend/catalog/dependency.c b/src/backend/catalog/dependency.c
index 18e07eb956a..bb14a438b0a 100644
--- a/src/backend/catalog/dependency.c
+++ b/src/backend/catalog/dependency.c
@@ -1238,6 +1238,12 @@ recordDependencyOnExpr(const ObjectAddress *depender,
  * range table.  An additional frammish is that dependencies on that
  * relation (or its component columns) will be marked with 'self_behavior',
  * whereas 'behavior' is used for everything else.
+ *
+ * NOTE: the caller should ensure that a whole-table dependency on the
+ * specified relation is created separately, if one is needed.  In particular,
+ * a whole-row Var "relation.*" will not cause this routine to emit any
+ * dependency item.  This is appropriate behavior for subexpressions of an
+ * ordinary query, so other cases need to cope as necessary.
  */
 void
 recordDependencyOnSingleRelExpr(const ObjectAddress *depender,
@@ -1350,7 +1356,14 @@ find_expr_references_walker(Node *node,
 
 		/*
 		 * A whole-row Var references no specific columns, so adds no new
-		 * dependency.
+		 * dependency.  (We assume that there is a whole-table dependency
+		 * arising from each underlying rangetable entry.  While we could
+		 * record such a dependency when finding a whole-row Var that
+		 * references a relation directly, it's quite unclear how to extend
+		 * that to whole-row Vars for JOINs, so it seems better to leave the
+		 * responsibility with the range table.  Note that this poses some
+		 * risks for identifying dependencies of stand-alone expressions:
+		 * whole-table references may need to be created separately.)
 		 */
 		if (var->varattno == InvalidAttrNumber)
 			return false;
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index b82b9b66fec..b437c9976a1 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -50,7 +50,6 @@
 #include "nodes/makefuncs.h"
 #include "nodes/nodeFuncs.h"
 #include "optimizer/clauses.h"
-#include "optimizer/var.h"
 #include "parser/parser.h"
 #include "storage/bufmgr.h"
 #include "storage/lmgr.h"
@@ -858,16 +857,12 @@ index_create(Oid heapRelationId,
 			}
 
 			/*
-			 * It's possible for an index to not depend on any columns of the
-			 * table at all, in which case we need to give it a dependency on
-			 * the table as a whole; else it won't get dropped when the table
-			 * is dropped.	This edge case is not totally useless; for
-			 * example, a unique index on a constant expression can serve to
-			 * prevent a table from containing more than one row.
+			 * If there are no simply-referenced columns, give the index an
+			 * auto dependency on the whole table.  In most cases, this will
+			 * be redundant, but it might not be if the index expressions and
+			 * predicate contain no Vars or only whole-row Vars.
 			 */
-			if (!have_simple_col &&
-			 !contain_vars_of_level((Node *) indexInfo->ii_Expressions, 0) &&
-				!contain_vars_of_level((Node *) indexInfo->ii_Predicate, 0))
+			if (!have_simple_col)
 			{
 				referenced.classId = RelationRelationId;
 				referenced.objectId = heapRelationId;
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index a5cc48b47cc..dc17685563b 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -240,6 +240,7 @@ static void get_opclass_name(Oid opclass, Oid actual_datatype,
 static Node *processIndirection(Node *node, deparse_context *context,
 				   bool printit);
 static void printSubscripts(ArrayRef *aref, deparse_context *context);
+static char *get_relation_name(Oid relid);
 static char *generate_relation_name(Oid relid, List *namespaces);
 static char *generate_function_name(Oid funcid, int nargs, List *argnames,
 					   Oid *argtypes, bool *is_variadic);
@@ -857,7 +858,7 @@ pg_get_indexdef_worker(Oid indexrelid, int colno,
 
 	indexpr_item = list_head(indexprs);
 
-	context = deparse_context_for(get_rel_name(indrelid), indrelid);
+	context = deparse_context_for(get_relation_name(indrelid), indrelid);
 
 	/*
 	 * Start the index definition.	Note that the index's name should never be
@@ -1261,7 +1262,7 @@ pg_get_constraintdef_worker(Oid constraintId, bool fullCommand,
 				if (conForm->conrelid != InvalidOid)
 				{
 					/* relation constraint */
-					context = deparse_context_for(get_rel_name(conForm->conrelid),
+					context = deparse_context_for(get_relation_name(conForm->conrelid),
 												  conForm->conrelid);
 				}
 				else
@@ -6314,7 +6315,7 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 			gavealias = true;
 		}
 		else if (rte->rtekind == RTE_RELATION &&
-				 strcmp(rte->eref->aliasname, get_rel_name(rte->relid)) != 0)
+				 strcmp(rte->eref->aliasname, get_relation_name(rte->relid)) != 0)
 		{
 			/*
 			 * Apparently the rel has been renamed since the rule was made.
@@ -6818,6 +6819,23 @@ quote_qualified_identifier(const char *qualifier,
 }
 
 /*
+ * get_relation_name
+ *		Get the unqualified name of a relation specified by OID
+ *
+ * This differs from the underlying get_rel_name() function in that it will
+ * throw error instead of silently returning NULL if the OID is bad.
+ */
+static char *
+get_relation_name(Oid relid)
+{
+	char	   *relname = get_rel_name(relid);
+
+	if (!relname)
+		elog(ERROR, "cache lookup failed for relation %u", relid);
+	return relname;
+}
+
+/*
  * generate_relation_name
  *		Compute the name to display for a relation specified by OID
  *