[BABEL] Add hook to enable index matching through type casts (babelfish-for-postgresql#762)

Adding a hook in match_opclause_to_indexcol() that allows babelfish to
provide index clauses when the built-in logic cannot match an OpExpr to
an index column. This enables extensions to handle type-cast patterns
that prevent index usage due to operator family mismatches.

Extension PR: babelfish-for-postgresql/babelfish_extensions#4829

Issues Resolved
Task: BABEL-6814

Authored-by: Rucha Kulkarni ruchask@amazon.com

Author: RuchaSK1

src/backend/optimizer/path/indxpath.c

@@ -37,6 +37,8 @@
 #include "utils/lsyscache.h"
 #include "utils/selfuncs.h"
 
+/* Hook for extensions to provide index clauses for unmatched OpExpr */
+match_opclause_to_indexcol_hook_type match_opclause_to_indexcol_hook = NULL;
 
 /* XXX see PartCollMatchesExprColl */
 #define IndexCollMatchesExprColl(idxcollation, exprcollation) \
@@ -2963,12 +2965,17 @@ match_opclause_to_indexcol(PlannerInfo *root,
 		 * function for the operator's underlying function.
 		 */
 		set_opfuncid(clause);	/* make sure we have opfuncid */
-		return get_index_clause_from_support(root,
+		iclause = get_index_clause_from_support(root,
 											 rinfo,
 											 clause->opfuncid,
 											 0, /* indexarg on left */
 											 indexcol,
 											 index);
+		if (iclause)
+			return iclause;
+		if (match_opclause_to_indexcol_hook)
+			return match_opclause_to_indexcol_hook(root, rinfo, indexcol, index);
+		return NULL;
 	}
 
 	if (match_index_to_operand(rightop, indexcol, index) &&
@@ -3003,12 +3010,17 @@ match_opclause_to_indexcol(PlannerInfo *root,
 		 * function for the operator's underlying function.
 		 */
 		set_opfuncid(clause);	/* make sure we have opfuncid */
-		return get_index_clause_from_support(root,
+		iclause = get_index_clause_from_support(root,
 											 rinfo,
 											 clause->opfuncid,
 											 1, /* indexarg on right */
 											 indexcol,
 											 index);
+		if (iclause)
+			return iclause;
+		if (match_opclause_to_indexcol_hook)
+			return match_opclause_to_indexcol_hook(root, rinfo, indexcol, index);
+		return NULL;
 	}
 
 	return NULL;

src/include/optimizer/paths.h

@@ -48,6 +48,13 @@ typedef RelOptInfo *(*join_search_hook_type) (PlannerInfo *root,
 											  List *initial_rels);
 extern PGDLLIMPORT join_search_hook_type join_search_hook;
 
+/* Hook for plugins to provide index clauses for unmatched OpExpr */
+typedef IndexClause *(*match_opclause_to_indexcol_hook_type) (PlannerInfo *root,
+																	 RestrictInfo *rinfo,
+																	 int indexcol,
+																	 IndexOptInfo *index);
+extern PGDLLIMPORT match_opclause_to_indexcol_hook_type match_opclause_to_indexcol_hook;
+
 
 extern RelOptInfo *make_one_rel(PlannerInfo *root, List *joinlist);
 extern RelOptInfo *standard_join_search(PlannerInfo *root, int levels_needed,