Refactor parser's generation of Var nodes.

Instead of passing around a pointer to the RangeTblEntry that
provides the desired column, pass a pointer to the associated
ParseNamespaceItem.  The RTE is trivially reachable from the nsitem,
and having the ParseNamespaceItem allows access to additional
information.  As proof of concept for that, add the rangetable index
to ParseNamespaceItem, and use that to get rid of RTERangeTablePosn
searches.

(I have in mind to teach the parser to generate some different
representation for Vars that are nullable by outer joins, and
keeping the necessary information in ParseNamespaceItems seems
like a reasonable approach to that.  But whether that ever
happens or not, this seems like good cleanup.)

Also refactor the code around scanRTEForColumn so that the
"fuzzy match" stuff does not leak out of parse_relation.c.

Discussion: https://postgr.es/m/26144.1576858373@sss.pgh.pa.us

1 files changed, 13 insertions, 30 deletions

diff --git a/src/include/parser/parse_relation.h b/src/include/parser/parse_relation.h
index f7e078172de..b09a71ea69f 100644
--- a/src/include/parser/parse_relation.h
+++ b/src/include/parser/parse_relation.h
@@ -17,45 +17,28 @@
 #include "parser/parse_node.h"
 
 
-/*
- * Support for fuzzily matching column.
- *
- * This is for building diagnostic messages, where non-exact matching
- * attributes are suggested to the user.  The struct's fields may be facets of
- * a particular RTE, or of an entire range table, depending on context.
- */
-typedef struct
-{
-	int			distance;		/* Weighted distance (lowest so far) */
-	RangeTblEntry *rfirst;		/* RTE of first */
-	AttrNumber	first;			/* Closest attribute so far */
-	RangeTblEntry *rsecond;		/* RTE of second */
-	AttrNumber	second;			/* Second closest attribute so far */
-} FuzzyAttrMatchState;
-
-
-extern RangeTblEntry *refnameRangeTblEntry(ParseState *pstate,
-										   const char *schemaname,
-										   const char *refname,
-										   int location,
-										   int *sublevels_up);
+extern ParseNamespaceItem *refnameNamespaceItem(ParseState *pstate,
+												const char *schemaname,
+												const char *refname,
+												int location,
+												int *sublevels_up);
 extern CommonTableExpr *scanNameSpaceForCTE(ParseState *pstate,
 											const char *refname,
 											Index *ctelevelsup);
 extern bool scanNameSpaceForENR(ParseState *pstate, const char *refname);
 extern void checkNameSpaceConflicts(ParseState *pstate, List *namespace1,
 									List *namespace2);
-extern int	RTERangeTablePosn(ParseState *pstate,
-							  RangeTblEntry *rte,
-							  int *sublevels_up);
+extern ParseNamespaceItem *GetNSItemByRangeTablePosn(ParseState *pstate,
+													 int varno,
+													 int sublevels_up);
 extern RangeTblEntry *GetRTEByRangeTablePosn(ParseState *pstate,
 											 int varno,
 											 int sublevels_up);
 extern CommonTableExpr *GetCTEForRTE(ParseState *pstate, RangeTblEntry *rte,
 									 int rtelevelsup);
-extern Node *scanRTEForColumn(ParseState *pstate, RangeTblEntry *rte,
-							  const char *colname, int location,
-							  int fuzzy_rte_penalty, FuzzyAttrMatchState *fuzzystate);
+extern Node *scanNSItemForColumn(ParseState *pstate, ParseNamespaceItem *nsitem,
+								 int sublevels_up, const char *colname,
+								 int location);
 extern Node *colNameToVar(ParseState *pstate, const char *colname, bool localonly,
 						  int location);
 extern void markVarForSelectPriv(ParseState *pstate, Var *var,
@@ -122,8 +105,8 @@ extern void errorMissingColumn(ParseState *pstate,
 extern void expandRTE(RangeTblEntry *rte, int rtindex, int sublevels_up,
 					  int location, bool include_dropped,
 					  List **colnames, List **colvars);
-extern List *expandRelAttrs(ParseState *pstate, RangeTblEntry *rte,
-							int rtindex, int sublevels_up, int location);
+extern List *expandNSItemAttrs(ParseState *pstate, ParseNamespaceItem *nsitem,
+							   int sublevels_up, int location);
 extern int	attnameAttNum(Relation rd, const char *attname, bool sysColOK);
 extern const NameData *attnumAttName(Relation rd, int attid);
 extern Oid	attnumTypeId(Relation rd, int attid);