Create an RTE field to record the query's lock mode for each relation.

Add RangeTblEntry.rellockmode, which records the appropriate lock mode for
each RTE_RELATION rangetable entry (either AccessShareLock, RowShareLock,
or RowExclusiveLock depending on the RTE's role in the query).

This patch creates the field and makes all creators of RTE nodes fill it
in reasonably, but for the moment nothing much is done with it.  The plan
is to replace assorted post-parser logic that re-determines the right
lockmode to use with simple uses of rte->rellockmode.  For now, just add
Asserts in each of those places that the rellockmode matches what they are
computing today.  (In some cases the match isn't perfect, so the Asserts
are weaker than you might expect; but this seems OK, as per discussion.)

This passes check-world for me, but it seems worth pushing in this state
to see if the buildfarm finds any problems in cases I failed to test.

catversion bump due to change of stored rules.

Amit Langote, reviewed by David Rowley and Jesper Pedersen,
and whacked around a bit more by me

Discussion: https://postgr.es/m/468c85d9-540e-66a2-1dde-fec2b741e688@lab.ntt.co.jp

1 files changed, 11 insertions, 0 deletions

diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 5443cbf67db..2b7cf263803 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -864,6 +864,7 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 			Relation	resultRelation;
 
 			resultRelationOid = getrelid(resultRelationIndex, rangeTable);
+			Assert(rt_fetch(resultRelationIndex, rangeTable)->rellockmode == RowExclusiveLock);
 			resultRelation = heap_open(resultRelationOid, RowExclusiveLock);
 
 			InitResultRelInfo(resultRelInfo,
@@ -904,6 +905,7 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 				Relation	resultRelDesc;
 
 				resultRelOid = getrelid(resultRelIndex, rangeTable);
+				Assert(rt_fetch(resultRelIndex, rangeTable)->rellockmode == RowExclusiveLock);
 				resultRelDesc = heap_open(resultRelOid, RowExclusiveLock);
 				InitResultRelInfo(resultRelInfo,
 								  resultRelDesc,
@@ -924,8 +926,11 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 				/* We locked the roots above. */
 				if (!list_member_int(plannedstmt->rootResultRelations,
 									 resultRelIndex))
+				{
+					Assert(rt_fetch(resultRelIndex, rangeTable)->rellockmode == RowExclusiveLock);
 					LockRelationOid(getrelid(resultRelIndex, rangeTable),
 									RowExclusiveLock);
+				}
 			}
 		}
 	}
@@ -955,6 +960,7 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 	{
 		PlanRowMark *rc = (PlanRowMark *) lfirst(l);
 		Oid			relid;
+		LOCKMODE	rellockmode;
 		Relation	relation;
 		ExecRowMark *erm;
 
@@ -964,6 +970,7 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 
 		/* get relation's OID (will produce InvalidOid if subquery) */
 		relid = getrelid(rc->rti, rangeTable);
+		rellockmode = rt_fetch(rc->rti, rangeTable)->rellockmode;
 
 		/*
 		 * If you change the conditions under which rel locks are acquired
@@ -975,9 +982,13 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 			case ROW_MARK_NOKEYEXCLUSIVE:
 			case ROW_MARK_SHARE:
 			case ROW_MARK_KEYSHARE:
+				Assert(rellockmode == RowShareLock);
 				relation = heap_open(relid, RowShareLock);
 				break;
 			case ROW_MARK_REFERENCE:
+				/* RTE might be a query target table */
+				Assert(rellockmode == AccessShareLock ||
+					   rellockmode == RowExclusiveLock);
 				relation = heap_open(relid, AccessShareLock);
 				break;
 			case ROW_MARK_COPY: