Improve representation of PlanRowMark.

This patch fixes two inadequacies of the PlanRowMark representation.

First, that the original LockingClauseStrength isn't stored (and cannot be
inferred for foreign tables, which always get ROW_MARK_COPY).  Since some
PlanRowMarks are created out of whole cloth and don't actually have an
ancestral RowMarkClause, this requires adding a dummy LCS_NONE value to
enum LockingClauseStrength, which is fairly annoying but the alternatives
seem worse.  This fix allows getting rid of the use of get_parse_rowmark()
in FDWs (as per the discussion around commits 462bd957 and
8ec8760f), and it simplifies some things elsewhere.

Second, that the representation assumed that all child tables in an
inheritance hierarchy would use the same RowMarkType.  That's true today
but will soon not be true.  We add an "allMarkTypes" field that identifies
the union of mark types used in all a parent table's children, and use
that where appropriate (currently, only in preprocess_targetlist()).

In passing fix a couple of minor infelicities left over from the SKIP
LOCKED patch, notably that _outPlanRowMark still thought waitPolicy
is a bool.

Catversion bump is required because the numeric values of enum
LockingClauseStrength can appear in on-disk rules.

Extracted from a much larger patch to support foreign table inheritance;
it seemed worth breaking this out, since it's a separable concern.

Shigeru Hanada and Etsuro Fujita, somewhat modified by me

contrib/postgres_fdw/postgres_fdw.c

@@ -822,13 +822,14 @@ postgresGetForeignPlan(PlannerInfo *root,
 	}
 	else
 	{
-		RowMarkClause *rc = get_parse_rowmark(root->parse, baserel->relid);
+		PlanRowMark *rc = get_plan_rowmark(root->rowMarks, baserel->relid);
 
 		if (rc)
 		{
 			/*
 			 * Relation is specified as a FOR UPDATE/SHARE target, so handle
-			 * that.
+			 * that.  (But we could also see LCS_NONE, meaning this isn't a
+			 * target relation after all.)
 			 *
 			 * For now, just ignore any [NO] KEY specification, since (a) it's
 			 * not clear what that means for a remote table that we don't have
@@ -837,6 +838,9 @@ postgresGetForeignPlan(PlannerInfo *root,
 			 */
 			switch (rc->strength)
 			{
+				case LCS_NONE:
+					/* No locking needed */
+					break;
 				case LCS_FORKEYSHARE:
 				case LCS_FORSHARE:
 					appendStringInfoString(&sql, " FOR SHARE");

src/backend/nodes/copyfuncs.c

@@ -991,6 +991,8 @@ _copyPlanRowMark(const PlanRowMark *from)
 	COPY_SCALAR_FIELD(prti);
 	COPY_SCALAR_FIELD(rowmarkId);
 	COPY_SCALAR_FIELD(markType);
+	COPY_SCALAR_FIELD(allMarkTypes);
+	COPY_SCALAR_FIELD(strength);
 	COPY_SCALAR_FIELD(waitPolicy);
 	COPY_SCALAR_FIELD(isParent);
 

src/backend/nodes/outfuncs.c

@@ -852,7 +852,9 @@ _outPlanRowMark(StringInfo str, const PlanRowMark *node)
 	WRITE_UINT_FIELD(prti);
 	WRITE_UINT_FIELD(rowmarkId);
 	WRITE_ENUM_FIELD(markType, RowMarkType);
-	WRITE_BOOL_FIELD(waitPolicy);
+	WRITE_INT_FIELD(allMarkTypes);
+	WRITE_ENUM_FIELD(strength, LockClauseStrength);
+	WRITE_ENUM_FIELD(waitPolicy, LockWaitPolicy);
 	WRITE_BOOL_FIELD(isParent);
 }
 

src/backend/optimizer/plan/planner.c

@@ -2219,35 +2219,42 @@ preprocess_rowmarks(PlannerInfo *root)
 		if (rte->rtekind != RTE_RELATION)
 			continue;
 
-		/*
-		 * Similarly, ignore RowMarkClauses for foreign tables; foreign tables
-		 * will instead get ROW_MARK_COPY items in the next loop.  (FDWs might
-		 * choose to do something special while fetching their rows, but that
-		 * is of no concern here.)
-		 */
-		if (rte->relkind == RELKIND_FOREIGN_TABLE)
-			continue;
-
 		rels = bms_del_member(rels, rc->rti);
 
 		newrc = makeNode(PlanRowMark);
 		newrc->rti = newrc->prti = rc->rti;
 		newrc->rowmarkId = ++(root->glob->lastRowMarkId);
+		if (rte->relkind == RELKIND_FOREIGN_TABLE)
+		{
+			/* For now, we force all foreign tables to use ROW_MARK_COPY */
+			newrc->markType = ROW_MARK_COPY;
+		}
+		else
+		{
+			/* regular table, apply the appropriate lock type */
 			switch (rc->strength)
 			{
-			case LCS_FORUPDATE:
-				newrc->markType = ROW_MARK_EXCLUSIVE;
+				case LCS_NONE:
+					/* we intentionally throw an error for LCS_NONE */
+					elog(ERROR, "unrecognized LockClauseStrength %d",
+						 (int) rc->strength);
 					break;
-			case LCS_FORNOKEYUPDATE:
-				newrc->markType = ROW_MARK_NOKEYEXCLUSIVE;
+				case LCS_FORKEYSHARE:
+					newrc->markType = ROW_MARK_KEYSHARE;
 					break;
 				case LCS_FORSHARE:
 					newrc->markType = ROW_MARK_SHARE;
 					break;
-			case LCS_FORKEYSHARE:
-				newrc->markType = ROW_MARK_KEYSHARE;
+				case LCS_FORNOKEYUPDATE:
+					newrc->markType = ROW_MARK_NOKEYEXCLUSIVE;
+					break;
+				case LCS_FORUPDATE:
+					newrc->markType = ROW_MARK_EXCLUSIVE;
 					break;
 			}
+		}
+		newrc->allMarkTypes = (1 << newrc->markType);
+		newrc->strength = rc->strength;
 		newrc->waitPolicy = rc->waitPolicy;
 		newrc->isParent = false;
 
@@ -2276,6 +2283,8 @@ preprocess_rowmarks(PlannerInfo *root)
 			newrc->markType = ROW_MARK_REFERENCE;
 		else
 			newrc->markType = ROW_MARK_COPY;
+		newrc->allMarkTypes = (1 << newrc->markType);
+		newrc->strength = LCS_NONE;
 		newrc->waitPolicy = LockWaitBlock;		/* doesn't matter */
 		newrc->isParent = false;
 

src/backend/optimizer/prep/prepsecurity.c

@@ -241,30 +241,10 @@ expand_security_qual(PlannerInfo *root, List *tlist, int rt_index,
 			rc = get_plan_rowmark(root->rowMarks, rt_index);
 			if (rc != NULL)
 			{
-				switch (rc->markType)
-				{
-					case ROW_MARK_EXCLUSIVE:
-						applyLockingClause(subquery, 1, LCS_FORUPDATE,
-										   rc->waitPolicy, false);
-						break;
-					case ROW_MARK_NOKEYEXCLUSIVE:
-						applyLockingClause(subquery, 1, LCS_FORNOKEYUPDATE,
-										   rc->waitPolicy, false);
-						break;
-					case ROW_MARK_SHARE:
-						applyLockingClause(subquery, 1, LCS_FORSHARE,
+				if (rc->strength != LCS_NONE)
+					applyLockingClause(subquery, 1, rc->strength,
 									   rc->waitPolicy, false);
-						break;
-					case ROW_MARK_KEYSHARE:
-						applyLockingClause(subquery, 1, LCS_FORKEYSHARE,
-										   rc->waitPolicy, false);
-						break;
-					case ROW_MARK_REFERENCE:
-					case ROW_MARK_COPY:
-						/* No locking needed */
-						break;
-				}
-				root->rowMarks = list_delete(root->rowMarks, rc);
+				root->rowMarks = list_delete_ptr(root->rowMarks, rc);
 			}
 
 			/*
@@ -276,6 +256,7 @@ expand_security_qual(PlannerInfo *root, List *tlist, int rt_index,
 			if (targetRelation)
 				applyLockingClause(subquery, 1, LCS_FORUPDATE,
 								   LockWaitBlock, false);
+
 			/*
 			 * Replace any variables in the outer query that refer to the
 			 * original relation RTE with references to columns that we will

src/backend/optimizer/prep/preptlist.c

@@ -92,9 +92,9 @@ preprocess_targetlist(PlannerInfo *root, List *tlist)
 		if (rc->rti != rc->prti)
 			continue;
 
-		if (rc->markType != ROW_MARK_COPY)
+		if (rc->allMarkTypes & ~(1 << ROW_MARK_COPY))
 		{
-			/* It's a regular table, so fetch its TID */
+			/* Need to fetch TID */
 			var = makeVar(rc->rti,
 						  SelfItemPointerAttributeNumber,
 						  TIDOID,
@@ -125,9 +125,9 @@ preprocess_targetlist(PlannerInfo *root, List *tlist)
 				tlist = lappend(tlist, tle);
 			}
 		}
-		else
+		if (rc->allMarkTypes & (1 << ROW_MARK_COPY))
 		{
-			/* Not a table, so we need the whole row as a junk var */
+			/* Need the whole row as a junk var */
 			var = makeWholeRowVar(rt_fetch(rc->rti, range_table),
 								  rc->rti,
 								  0,

src/backend/optimizer/prep/prepunion.c

@@ -1389,9 +1389,14 @@ expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte, Index rti)
 			newrc->prti = rti;
 			newrc->rowmarkId = oldrc->rowmarkId;
 			newrc->markType = oldrc->markType;
+			newrc->allMarkTypes = (1 << newrc->markType);
+			newrc->strength = oldrc->strength;
 			newrc->waitPolicy = oldrc->waitPolicy;
 			newrc->isParent = false;
 
+			/* Include child's rowmark type in parent's allMarkTypes */
+			oldrc->allMarkTypes |= newrc->allMarkTypes;
+
 			root->rowMarks = lappend(root->rowMarks, newrc);
 		}
 

src/backend/parser/analyze.c

@@ -2254,11 +2254,18 @@ transformCreateTableAsStmt(ParseState *pstate, CreateTableAsStmt *stmt)
 }
 
 
-char *
+/*
+ * Produce a string representation of a LockClauseStrength value.
+ * This should only be applied to valid values (not LCS_NONE).
+ */
+const char *
 LCS_asString(LockClauseStrength strength)
 {
 	switch (strength)
 	{
+		case LCS_NONE:
+			Assert(false);
+			break;
 		case LCS_FORKEYSHARE:
 			return "FOR KEY SHARE";
 		case LCS_FORSHARE:
@@ -2279,6 +2286,8 @@ LCS_asString(LockClauseStrength strength)
 void
 CheckSelectLocking(Query *qry, LockClauseStrength strength)
 {
+	Assert(strength != LCS_NONE);		/* else caller error */
+
 	if (qry->setOperations)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -2498,6 +2507,8 @@ applyLockingClause(Query *qry, Index rtindex,
 {
 	RowMarkClause *rc;
 
+	Assert(strength != LCS_NONE);		/* else caller error */
+
 	/* If it's an explicit clause, make sure hasForUpdate gets set */
 	if (!pushedDown)
 		qry->hasForUpdate = true;
@@ -2506,20 +2517,21 @@ applyLockingClause(Query *qry, Index rtindex,
 	if ((rc = get_parse_rowmark(qry, rtindex)) != NULL)
 	{
 		/*
-		 * If the same RTE is specified for more than one locking strength,
-		 * treat is as the strongest.  (Reasonable, since you can't take both
-		 * a shared and exclusive lock at the same time; it'll end up being
-		 * exclusive anyway.)
+		 * If the same RTE is specified with more than one locking strength,
+		 * use the strongest.  (Reasonable, since you can't take both a shared
+		 * and exclusive lock at the same time; it'll end up being exclusive
+		 * anyway.)
 		 *
-		 * Similarly, if the same RTE is specified with more than one lock wait
-		 * policy, consider that NOWAIT wins over SKIP LOCKED, which in turn
-		 * wins over waiting for the lock (the default).  This is a bit more
-		 * debatable but raising an error doesn't seem helpful.  (Consider for
-		 * instance SELECT FOR UPDATE NOWAIT from a view that internally
+		 * Similarly, if the same RTE is specified with more than one lock
+		 * wait policy, consider that NOWAIT wins over SKIP LOCKED, which in
+		 * turn wins over waiting for the lock (the default).  This is a bit
+		 * more debatable but raising an error doesn't seem helpful. (Consider
+		 * for instance SELECT FOR UPDATE NOWAIT from a view that internally
 		 * contains a plain FOR UPDATE spec.)  Having NOWAIT win over SKIP
 		 * LOCKED is reasonable since the former throws an error in case of
-		 * coming across a locked tuple, which may be undesirable in some cases
-		 * but it seems better than silently returning inconsistent results.
+		 * coming across a locked tuple, which may be undesirable in some
+		 * cases but it seems better than silently returning inconsistent
+		 * results.
 		 *
 		 * And of course pushedDown becomes false if any clause is explicit.
 		 */

src/backend/tcop/utility.c

@@ -2395,26 +2395,22 @@ CreateCommandTag(Node *parsetree)
 						else if (stmt->rowMarks != NIL)
 						{
 							/* not 100% but probably close enough */
-							switch (((PlanRowMark *) linitial(stmt->rowMarks))->markType)
+							switch (((PlanRowMark *) linitial(stmt->rowMarks))->strength)
 							{
-								case ROW_MARK_EXCLUSIVE:
-									tag = "SELECT FOR UPDATE";
-									break;
-								case ROW_MARK_NOKEYEXCLUSIVE:
-									tag = "SELECT FOR NO KEY UPDATE";
+								case LCS_FORKEYSHARE:
+									tag = "SELECT FOR KEY SHARE";
 									break;
-								case ROW_MARK_SHARE:
+								case LCS_FORSHARE:
 									tag = "SELECT FOR SHARE";
 									break;
-								case ROW_MARK_KEYSHARE:
-									tag = "SELECT FOR KEY SHARE";
+								case LCS_FORNOKEYUPDATE:
+									tag = "SELECT FOR NO KEY UPDATE";
 									break;
-								case ROW_MARK_REFERENCE:
-								case ROW_MARK_COPY:
-									tag = "SELECT";
+								case LCS_FORUPDATE:
+									tag = "SELECT FOR UPDATE";
 									break;
 								default:
-									tag = "???";
+									tag = "SELECT";
 									break;
 							}
 						}

src/backend/utils/adt/ruleutils.c

@@ -4453,6 +4453,11 @@ get_select_query_def(Query *query, deparse_context *context,
 
 			switch (rc->strength)
 			{
+				case LCS_NONE:
+					/* we intentionally throw an error for LCS_NONE */
+					elog(ERROR, "unrecognized LockClauseStrength %d",
+						 (int) rc->strength);
+					break;
 				case LCS_FORKEYSHARE:
 					appendContextKeyword(context, " FOR KEY SHARE",
 									 -PRETTYINDENT_STD, PRETTYINDENT_STD, 0);

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201503061
+#define CATALOG_VERSION_NO	201503151
 
 #endif

src/include/nodes/lockoptions.h

@@ -20,6 +20,7 @@
  */
 typedef enum LockClauseStrength
 {
+	LCS_NONE,					/* no such clause - only used in PlanRowMark */
 	LCS_FORKEYSHARE,			/* FOR KEY SHARE */
 	LCS_FORSHARE,				/* FOR SHARE */
 	LCS_FORNOKEYUPDATE,			/* FOR NO KEY UPDATE */

src/include/nodes/plannodes.h

@@ -820,7 +820,7 @@ typedef enum RowMarkType
 	ROW_MARK_NOKEYEXCLUSIVE,	/* obtain no-key exclusive tuple lock */
 	ROW_MARK_SHARE,				/* obtain shared tuple lock */
 	ROW_MARK_KEYSHARE,			/* obtain keyshare tuple lock */
-	ROW_MARK_REFERENCE,			/* just fetch the TID */
+	ROW_MARK_REFERENCE,			/* just fetch the TID, don't lock it */
 	ROW_MARK_COPY				/* physically copy the row value */
 } RowMarkType;
 
@@ -841,7 +841,9 @@ typedef enum RowMarkType
  * list for each child relation (including the target rel itself in its role
  * as a child).  The child entries have rti == child rel's RT index and
  * prti == parent's RT index, and can therefore be recognized as children by
- * the fact that prti != rti.
+ * the fact that prti != rti.  The parent's allMarkTypes field gets the OR
+ * of (1<<markType) across all its children (this definition allows children
+ * to use different markTypes).
  *
  * The planner also adds resjunk output columns to the plan that carry
  * information sufficient to identify the locked or fetched rows.  For
@@ -851,6 +853,8 @@ typedef enum RowMarkType
  * The tableoid column is only present for an inheritance hierarchy.
  * When markType == ROW_MARK_COPY, there is instead a single column named
  *		wholerow%u			whole-row value of relation
+ * (An inheritance hierarchy could have all three resjunk output columns,
+ * if some children use a different markType than others.)
  * In all three cases, %u represents the rowmark ID number (rowmarkId).
  * This number is unique within a plan tree, except that child relation
  * entries copy their parent's rowmarkId.  (Assigning unique numbers
@@ -867,6 +871,8 @@ typedef struct PlanRowMark
 	Index		prti;			/* range table index of parent relation */
 	Index		rowmarkId;		/* unique identifier for resjunk columns */
 	RowMarkType markType;		/* see enum above */
+	int			allMarkTypes;	/* OR of (1<<markType) for all children */
+	LockClauseStrength strength;	/* LockingClause's strength, or LCS_NONE */
 	LockWaitPolicy waitPolicy;	/* NOWAIT and SKIP LOCKED options */
 	bool		isParent;		/* true if this is a "dummy" parent entry */
 } PlanRowMark;

src/include/parser/analyze.h

@@ -36,7 +36,7 @@ extern Query *transformStmt(ParseState *pstate, Node *parseTree);
 
 extern bool analyze_requires_snapshot(Node *parseTree);
 
-extern char *LCS_asString(LockClauseStrength strength);
+extern const char *LCS_asString(LockClauseStrength strength);
 extern void CheckSelectLocking(Query *qry, LockClauseStrength strength);
 extern void applyLockingClause(Query *qry, Index rtindex,
 				   LockClauseStrength strength,