Stop accessing checkAsUser via RTE in some cases

A future commit will move the checkAsUser field from RangeTblEntry
to a new node that, unlike RTEs, will only be created for tables
mentioned in the query but not for the inheritance child relations
added to the query by the planner.  So, checkAsUser value for a
given child relation will have to be obtained by referring to that
for its ancestor mentioned in the query.

In preparation, it seems better to expand the use of RelOptInfo.userid
during planning in place of rte->checkAsUser so that there will be
fewer places to adjust for the above change.

Given that the child-to-ancestor mapping is not available during the
execution of a given "child" ForeignScan node, add a checkAsUser
field to ForeignScan to carry the child relation's RelOptInfo.userid.

Author: Amit Langote <amitlangote09@gmail.com>
Discussion: https://postgr.es/m/CA+HiwqGFCs2uq7VRKi7g+FFKbP6Ea_2_HkgZb2HPhUfaAKT3ng@mail.gmail.com

1 files changed, 7 insertions, 11 deletions

diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index 8d7500abfbd..20c7b1ad05a 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -624,7 +624,6 @@ postgresGetForeignRelSize(PlannerInfo *root,
 {
 	PgFdwRelationInfo *fpinfo;
 	ListCell   *lc;
-	RangeTblEntry *rte = planner_rt_fetch(baserel->relid, root);
 
 	/*
 	 * We use PgFdwRelationInfo to pass various information to subsequent
@@ -663,8 +662,9 @@ postgresGetForeignRelSize(PlannerInfo *root,
 	 */
 	if (fpinfo->use_remote_estimate)
 	{
-		Oid			userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
+		Oid			userid;
 
+		userid = OidIsValid(baserel->userid) ? baserel->userid : GetUserId();
 		fpinfo->user = GetUserMapping(userid, fpinfo->server->serverid);
 	}
 	else
@@ -1510,16 +1510,14 @@ postgresBeginForeignScan(ForeignScanState *node, int eflags)
 
 	/*
 	 * Identify which user to do the remote access as.  This should match what
-	 * ExecCheckRTEPerms() does.  In case of a join or aggregate, use the
-	 * lowest-numbered member RTE as a representative; we would get the same
-	 * result from any.
+	 * ExecCheckRTEPerms() does.
 	 */
+	userid = OidIsValid(fsplan->checkAsUser) ? fsplan->checkAsUser : GetUserId();
 	if (fsplan->scan.scanrelid > 0)
 		rtindex = fsplan->scan.scanrelid;
 	else
 		rtindex = bms_next_member(fsplan->fs_relids, -1);
 	rte = exec_rt_fetch(rtindex, estate);
-	userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
 
 	/* Get info about foreign table. */
 	table = GetForeignTable(rte->relid);
@@ -2633,7 +2631,6 @@ postgresBeginDirectModify(ForeignScanState *node, int eflags)
 	EState	   *estate = node->ss.ps.state;
 	PgFdwDirectModifyState *dmstate;
 	Index		rtindex;
-	RangeTblEntry *rte;
 	Oid			userid;
 	ForeignTable *table;
 	UserMapping *user;
@@ -2655,11 +2652,10 @@ postgresBeginDirectModify(ForeignScanState *node, int eflags)
 	 * Identify which user to do the remote access as.  This should match what
 	 * ExecCheckRTEPerms() does.
 	 */
-	rtindex = node->resultRelInfo->ri_RangeTableIndex;
-	rte = exec_rt_fetch(rtindex, estate);
-	userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
+	userid = OidIsValid(fsplan->checkAsUser) ? fsplan->checkAsUser : GetUserId();
 
 	/* Get info about foreign table. */
+	rtindex = node->resultRelInfo->ri_RangeTableIndex;
 	if (fsplan->scan.scanrelid == 0)
 		dmstate->rel = ExecOpenScanRelation(estate, rtindex, eflags);
 	else
@@ -3983,7 +3979,7 @@ create_foreign_modify(EState *estate,
 	 * Identify which user to do the remote access as.  This should match what
 	 * ExecCheckRTEPerms() does.
 	 */
-	userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
+	userid = OidIsValid(rte->checkAsUser) ? rte->checkAsUser : GetUserId();
 
 	/* Get info about foreign table. */
 	table = GetForeignTable(RelationGetRelid(rel));