Rework query relation permission checking

Currently, information about the permissions to be checked on relations
mentioned in a query is stored in their range table entries.  So the
executor must scan the entire range table looking for relations that
need to have permissions checked.  This can make the permission checking
part of the executor initialization needlessly expensive when many
inheritance children are present in the range range.  While the
permissions need not be checked on the individual child relations, the
executor still must visit every range table entry to filter them out.

This commit moves the permission checking information out of the range
table entries into a new plan node called RTEPermissionInfo.  Every
top-level (inheritance "root") RTE_RELATION entry in the range table
gets one and a list of those is maintained alongside the range table.
This new list is initialized by the parser when initializing the range
table.  The rewriter can add more entries to it as rules/views are
expanded.  Finally, the planner combines the lists of the individual
subqueries into one flat list that is passed to the executor for
checking.

To make it quick to find the RTEPermissionInfo entry belonging to a
given relation, RangeTblEntry gets a new Index field 'perminfoindex'
that stores the corresponding RTEPermissionInfo's index in the query's
list of the latter.

ExecutorCheckPerms_hook has gained another List * argument; the
signature is now:
typedef bool (*ExecutorCheckPerms_hook_type) (List *rangeTable,
					      List *rtePermInfos,
					      bool ereport_on_violation);
The first argument is no longer used by any in-core uses of the hook,
but we leave it in place because there may be other implementations that
do.  Implementations should likely scan the rtePermInfos list to
determine which operations to allow or deny.

Author: Amit Langote <amitlangote09@gmail.com>
Discussion: https://postgr.es/m/CA+HiwqGjJDmUhDSfv-U2qhKJjt9ST7Xh9JXC_irsAQ1TAUsJYg@mail.gmail.com

1 files changed, 90 insertions, 44 deletions

diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c
index 572c87e4536..e296f44ebd9 100644
--- a/src/backend/executor/execUtils.c
+++ b/src/backend/executor/execUtils.c
@@ -57,6 +57,7 @@
 #include "miscadmin.h"
 #include "nodes/nodeFuncs.h"
 #include "parser/parsetree.h"
+#include "parser/parse_relation.h"
 #include "partitioning/partdesc.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -67,6 +68,7 @@
 
 static bool tlist_matches_tupdesc(PlanState *ps, List *tlist, int varno, TupleDesc tupdesc);
 static void ShutdownExprContext(ExprContext *econtext, bool isCommit);
+static RTEPermissionInfo *GetResultRTEPermissionInfo(ResultRelInfo *relinfo, EState *estate);
 
 
 /* ----------------------------------------------------------------
@@ -1296,72 +1298,48 @@ ExecGetRootToChildMap(ResultRelInfo *resultRelInfo, EState *estate)
 Bitmapset *
 ExecGetInsertedCols(ResultRelInfo *relinfo, EState *estate)
 {
-	/*
-	 * The columns are stored in the range table entry.  If this ResultRelInfo
-	 * represents a partition routing target, and doesn't have an entry of its
-	 * own in the range table, fetch the parent's RTE and map the columns to
-	 * the order they are in the partition.
-	 */
-	if (relinfo->ri_RangeTableIndex != 0)
-	{
-		RangeTblEntry *rte = exec_rt_fetch(relinfo->ri_RangeTableIndex, estate);
+	RTEPermissionInfo *perminfo = GetResultRTEPermissionInfo(relinfo, estate);
 
-		return rte->insertedCols;
-	}
-	else if (relinfo->ri_RootResultRelInfo)
+	if (perminfo == NULL)
+		return NULL;
+
+	/* Map the columns to child's attribute numbers if needed. */
+	if (relinfo->ri_RootResultRelInfo)
 	{
-		ResultRelInfo *rootRelInfo = relinfo->ri_RootResultRelInfo;
-		RangeTblEntry *rte = exec_rt_fetch(rootRelInfo->ri_RangeTableIndex, estate);
 		TupleConversionMap *map = ExecGetRootToChildMap(relinfo, estate);
 
-		if (map != NULL)
-			return execute_attr_map_cols(map->attrMap, rte->insertedCols);
-		else
-			return rte->insertedCols;
-	}
-	else
-	{
-		/*
-		 * The relation isn't in the range table and it isn't a partition
-		 * routing target.  This ResultRelInfo must've been created only for
-		 * firing triggers and the relation is not being inserted into.  (See
-		 * ExecGetTriggerResultRel.)
-		 */
-		return NULL;
+		if (map)
+			return execute_attr_map_cols(map->attrMap, perminfo->insertedCols);
 	}
+
+	return perminfo->insertedCols;
 }
 
 /* Return a bitmap representing columns being updated */
 Bitmapset *
 ExecGetUpdatedCols(ResultRelInfo *relinfo, EState *estate)
 {
-	/* see ExecGetInsertedCols() */
-	if (relinfo->ri_RangeTableIndex != 0)
-	{
-		RangeTblEntry *rte = exec_rt_fetch(relinfo->ri_RangeTableIndex, estate);
+	RTEPermissionInfo *perminfo = GetResultRTEPermissionInfo(relinfo, estate);
 
-		return rte->updatedCols;
-	}
-	else if (relinfo->ri_RootResultRelInfo)
+	if (perminfo == NULL)
+		return NULL;
+
+	/* Map the columns to child's attribute numbers if needed. */
+	if (relinfo->ri_RootResultRelInfo)
 	{
-		ResultRelInfo *rootRelInfo = relinfo->ri_RootResultRelInfo;
-		RangeTblEntry *rte = exec_rt_fetch(rootRelInfo->ri_RangeTableIndex, estate);
 		TupleConversionMap *map = ExecGetRootToChildMap(relinfo, estate);
 
-		if (map != NULL)
-			return execute_attr_map_cols(map->attrMap, rte->updatedCols);
-		else
-			return rte->updatedCols;
+		if (map)
+			return execute_attr_map_cols(map->attrMap, perminfo->updatedCols);
 	}
-	else
-		return NULL;
+
+	return perminfo->updatedCols;
 }
 
 /* Return a bitmap representing generated columns being updated */
 Bitmapset *
 ExecGetExtraUpdatedCols(ResultRelInfo *relinfo, EState *estate)
 {
-	/* see ExecGetInsertedCols() */
 	if (relinfo->ri_RangeTableIndex != 0)
 	{
 		RangeTblEntry *rte = exec_rt_fetch(relinfo->ri_RangeTableIndex, estate);
@@ -1390,3 +1368,71 @@ ExecGetAllUpdatedCols(ResultRelInfo *relinfo, EState *estate)
 	return bms_union(ExecGetUpdatedCols(relinfo, estate),
 					 ExecGetExtraUpdatedCols(relinfo, estate));
 }
+
+/*
+ * GetResultRTEPermissionInfo
+ *		Looks up RTEPermissionInfo for ExecGet*Cols() routines
+ */
+static RTEPermissionInfo *
+GetResultRTEPermissionInfo(ResultRelInfo *relinfo, EState *estate)
+{
+	Index		rti;
+	RangeTblEntry *rte;
+	RTEPermissionInfo *perminfo = NULL;
+
+	if (relinfo->ri_RootResultRelInfo)
+	{
+		/*
+		 * For inheritance child result relations (a partition routing target
+		 * of an INSERT or a child UPDATE target), this returns the root
+		 * parent's RTE to fetch the RTEPermissionInfo because that's the only
+		 * one that has one assigned.
+		 */
+		rti = relinfo->ri_RootResultRelInfo->ri_RangeTableIndex;
+	}
+	else if (relinfo->ri_RangeTableIndex != 0)
+	{
+		/*
+		 * Non-child result relation should have their own RTEPermissionInfo.
+		 */
+		rti = relinfo->ri_RangeTableIndex;
+	}
+	else
+	{
+		/*
+		 * The relation isn't in the range table and it isn't a partition
+		 * routing target.  This ResultRelInfo must've been created only for
+		 * firing triggers and the relation is not being inserted into.  (See
+		 * ExecGetTriggerResultRel.)
+		 */
+		rti = 0;
+	}
+
+	if (rti > 0)
+	{
+		rte = exec_rt_fetch(rti, estate);
+		perminfo = getRTEPermissionInfo(estate->es_rteperminfos, rte);
+	}
+
+	return perminfo;
+}
+
+/*
+ * GetResultRelCheckAsUser
+ *		Returns the user to modify passed-in result relation as
+ *
+ * The user is chosen by looking up the relation's or, if a child table, its
+ * root parent's RTEPermissionInfo.
+ */
+Oid
+ExecGetResultRelCheckAsUser(ResultRelInfo *relInfo, EState *estate)
+{
+	RTEPermissionInfo *perminfo = GetResultRTEPermissionInfo(relInfo, estate);
+
+	/* XXX - maybe ok to return GetUserId() in this case? */
+	if (perminfo == NULL)
+		elog(ERROR, "no RTEPermissionInfo found for result relation with OID %u",
+			 RelationGetRelid(relInfo->ri_RelationDesc));
+
+	return perminfo->checkAsUser ? perminfo->checkAsUser : GetUserId();
+}