When index recurses to a partition, map columns numbers

Two out of three code paths were mapping column numbers correctly if a
partition had different column numbers than parent table, but the most
commonly used one (recursing in CREATE INDEX to a new index on a
partition) failed to map attribute numbers in expressions.  Oddly
enough, attnums in WHERE clauses are already handled correctly
everywhere.

Reported-by: Amit Langote
Author: Amit Langote
Discussion: https://postgr.es/m/dce1fda4-e0f0-94c9-6abb-f5956a98c057@lab.ntt.co.jp
Reviewed-by: Álvaro Herrera

src/backend/commands/indexcmds.c

@@ -993,7 +993,32 @@ DefineIndex(Oid relationId,
 				{
 					IndexStmt  *childStmt = copyObject(stmt);
 					bool		found_whole_row;
+					ListCell   *lc;
 
+					/*
+					 * Adjust any Vars (both in expressions and in the index's
+					 * WHERE clause) to match the partition's column numbering
+					 * in case it's different from the parent's.
+					 */
+					foreach(lc, childStmt->indexParams)
+					{
+						IndexElem *ielem = lfirst(lc);
+
+						/*
+						 * If the index parameter is an expression, we must
+						 * translate it to contain child Vars.
+						 */
+						if (ielem->expr)
+						{
+							ielem->expr =
+								map_variable_attnos((Node *) ielem->expr,
+													1, 0, attmap, maplen,
+													InvalidOid,
+													&found_whole_row);
+							if (found_whole_row)
+								elog(ERROR, "cannot convert whole-row table reference");
+						}
+					}
 					childStmt->whereClause =
 						map_variable_attnos(stmt->whereClause, 1, 0,
 											attmap, maplen,

src/test/regress/expected/indexing.out

@@ -631,17 +631,21 @@ alter table idxpart2 drop column col1, drop column col2;
 create index on idxpart2 (abs(b));
 alter table idxpart attach partition idxpart2 for values from (0) to (1);
 create index on idxpart (abs(b));
+create index on idxpart ((b + 1));
 alter table idxpart attach partition idxpart1 for values from (1) to (2);
 select c.relname, pg_get_indexdef(indexrelid)
   from pg_class c join pg_index i on c.oid = i.indexrelid
   where indrelid::regclass::text like 'idxpart%'
   order by indexrelid::regclass::text collate "C";
       relname      |                               pg_get_indexdef                                
-------------------+--------------------------------------------------------------------------
+-------------------+------------------------------------------------------------------------------
  idxpart1_abs_idx  | CREATE INDEX idxpart1_abs_idx ON public.idxpart1 USING btree (abs(b))
+ idxpart1_expr_idx | CREATE INDEX idxpart1_expr_idx ON public.idxpart1 USING btree (((b + 1)))
  idxpart2_abs_idx  | CREATE INDEX idxpart2_abs_idx ON public.idxpart2 USING btree (abs(b))
+ idxpart2_expr_idx | CREATE INDEX idxpart2_expr_idx ON public.idxpart2 USING btree (((b + 1)))
  idxpart_abs_idx   | CREATE INDEX idxpart_abs_idx ON ONLY public.idxpart USING btree (abs(b))
-(3 rows)
+ idxpart_expr_idx  | CREATE INDEX idxpart_expr_idx ON ONLY public.idxpart USING btree (((b + 1)))
+(6 rows)
 
 drop table idxpart;
 -- Verify that columns are mapped correctly for WHERE in a partial index

src/test/regress/sql/indexing.sql

@@ -326,6 +326,7 @@ alter table idxpart2 drop column col1, drop column col2;
 create index on idxpart2 (abs(b));
 alter table idxpart attach partition idxpart2 for values from (0) to (1);
 create index on idxpart (abs(b));
+create index on idxpart ((b + 1));
 alter table idxpart attach partition idxpart1 for values from (1) to (2);
 select c.relname, pg_get_indexdef(indexrelid)
   from pg_class c join pg_index i on c.oid = i.indexrelid