Refactor ON CONFLICT index inference parse tree representation.

Defer lookup of opfamily and input type of a of a user specified opclass
until the optimizer selects among available unique indexes; and store
the opclass in the parse analyzed tree instead.  The primary reason for
doing this is that for rule deparsing it's easier to use the opclass
than the previous representation.

While at it also rename a variable in the inference code to better fit
it's purpose.

This is separate from the actual fixes for deparsing to make review
easier.

7 files changed, 30 insertions, 33 deletions

diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index d36be3c806..2d9bf419bd 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -1839,8 +1839,7 @@ _copyInferenceElem(const InferenceElem *from)
 
 	COPY_NODE_FIELD(expr);
 	COPY_SCALAR_FIELD(infercollid);
-	COPY_SCALAR_FIELD(inferopfamily);
-	COPY_SCALAR_FIELD(inferopcinputtype);
+	COPY_SCALAR_FIELD(inferopclass);
 
 	return newnode;
 }
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index d7928a9917..f19251e7c4 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -702,8 +702,7 @@ _equalInferenceElem(const InferenceElem *a, const InferenceElem *b)
 {
 	COMPARE_NODE_FIELD(expr);
 	COMPARE_SCALAR_FIELD(infercollid);
-	COMPARE_SCALAR_FIELD(inferopfamily);
-	COMPARE_SCALAR_FIELD(inferopcinputtype);
+	COMPARE_SCALAR_FIELD(inferopclass);
 
 	return true;
 }
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index fdd6032b4c..54464f8c65 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -1474,8 +1474,7 @@ _outInferenceElem(StringInfo str, const InferenceElem *node)
 
 	WRITE_NODE_FIELD(expr);
 	WRITE_OID_FIELD(infercollid);
-	WRITE_OID_FIELD(inferopfamily);
-	WRITE_OID_FIELD(inferopcinputtype);
+	WRITE_OID_FIELD(inferopclass);
 }
 
 static void
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 6fd9d46ee7..f5a40fbfb4 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -1214,8 +1214,7 @@ _readInferenceElem(void)
 
 	READ_NODE_FIELD(expr);
 	READ_OID_FIELD(infercollid);
-	READ_OID_FIELD(inferopfamily);
-	READ_OID_FIELD(inferopcinputtype);
+	READ_OID_FIELD(inferopclass);
 
 	READ_DONE();
 }
diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index b425680f47..a857ba3526 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -438,8 +438,8 @@ infer_arbiter_indexes(PlannerInfo *root)
 	Bitmapset  *inferAttrs = NULL;
 	List	   *inferElems = NIL;
 
-	/* Result */
-	List	   *candidates = NIL;
+	/* Results */
+	List	   *results = NIL;
 
 	/*
 	 * Quickly return NIL for ON CONFLICT DO NOTHING without an inference
@@ -565,11 +565,11 @@ infer_arbiter_indexes(PlannerInfo *root)
 						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 						 errmsg("ON CONFLICT DO UPDATE not supported with exclusion constraints")));
 
-			candidates = lappend_oid(candidates, idxForm->indexrelid);
+			results = lappend_oid(results, idxForm->indexrelid);
 			list_free(indexList);
 			index_close(idxRel, NoLock);
 			heap_close(relation, NoLock);
-			return candidates;
+			return results;
 		}
 		else if (indexOidFromConstraint != InvalidOid)
 		{
@@ -633,7 +633,7 @@ infer_arbiter_indexes(PlannerInfo *root)
 			 * index definition.
 			 */
 			if (elem->infercollid != InvalidOid ||
-				elem->inferopfamily != InvalidOid ||
+				elem->inferopclass != InvalidOid ||
 				list_member(idxExprs, elem->expr))
 				continue;
 
@@ -660,7 +660,7 @@ infer_arbiter_indexes(PlannerInfo *root)
 		if (!predicate_implied_by(predExprs, whereExplicit))
 			goto next;
 
-		candidates = lappend_oid(candidates, idxForm->indexrelid);
+		results = lappend_oid(results, idxForm->indexrelid);
 next:
 		index_close(idxRel, NoLock);
 	}
@@ -668,12 +668,12 @@ next:
 	list_free(indexList);
 	heap_close(relation, NoLock);
 
-	if (candidates == NIL)
+	if (results == NIL)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
 				 errmsg("there is no unique or exclusion constraint matching the ON CONFLICT specification")));
 
-	return candidates;
+	return results;
 }
 
 /*
@@ -709,23 +709,33 @@ infer_collation_opclass_match(InferenceElem *elem, Relation idxRel,
 							  Bitmapset *inferAttrs, List *idxExprs)
 {
 	AttrNumber	natt;
+	Oid			inferopfamily = InvalidOid;		/* OID of att opfamily */
+	Oid			inferopcinputtype = InvalidOid;		/* OID of att opfamily */
 
 	/*
 	 * If inference specification element lacks collation/opclass, then no
 	 * need to check for exact match.
 	 */
-	if (elem->infercollid == InvalidOid && elem->inferopfamily == InvalidOid)
+	if (elem->infercollid == InvalidOid && elem->inferopclass == InvalidOid)
 		return true;
 
+	/*
+	 * Lookup opfamily and input type, for matching indexes
+	 */
+	if (elem->inferopclass)
+	{
+		inferopfamily = get_opclass_family(elem->inferopclass);
+		inferopcinputtype = get_opclass_input_type(elem->inferopclass);
+	}
+
 	for (natt = 1; natt <= idxRel->rd_att->natts; natt++)
 	{
 		Oid		opfamily = idxRel->rd_opfamily[natt - 1];
 		Oid		opcinputtype = idxRel->rd_opcintype[natt - 1];
 		Oid		collation = idxRel->rd_indcollation[natt - 1];
 
-		if (elem->inferopfamily != InvalidOid &&
-			(elem->inferopfamily != opfamily ||
-			 elem->inferopcinputtype != opcinputtype))
+		if (elem->inferopclass != InvalidOid &&
+			(inferopfamily != opfamily || inferopcinputtype != opcinputtype))
 		{
 			/* Attribute needed to match opclass, but didn't */
 			continue;
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index a90bcf40c9..c8af5ab1d0 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -2730,18 +2730,10 @@ resolve_unique_index_expr(ParseState *pstate, InferClause *infer,
 												  exprLocation(pInfer->expr));
 
 		if (!ielem->opclass)
-		{
-			pInfer->inferopfamily = InvalidOid;
-			pInfer->inferopcinputtype = InvalidOid;
-		}
+			pInfer->inferopclass = InvalidOid;
 		else
-		{
-			Oid		opclass = get_opclass_oid(BTREE_AM_OID, ielem->opclass,
-											  false);
-
-			pInfer->inferopfamily = get_opclass_family(opclass);
-			pInfer->inferopcinputtype = get_opclass_input_type(opclass);
-		}
+			pInfer->inferopclass = get_opclass_oid(BTREE_AM_OID,
+												   ielem->opclass, false);
 
 		result = lappend(result, pInfer);
 	}
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index a5467c5379..9f3a7267a2 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -1198,8 +1198,7 @@ typedef struct InferenceElem
 	Expr		xpr;
 	Node	   *expr;				/* expression to infer from, or NULL */
 	Oid			infercollid;		/* OID of collation, or InvalidOid */
-	Oid			inferopfamily;		/* OID of att opfamily, or InvalidOid */
-	Oid			inferopcinputtype;	/* OID of att input type, or InvalidOid */
+	Oid			inferopclass;		/* OID of att opclass, or InvalidOid */
 } InferenceElem;
 
 /*--------------------