[#21892] YSQL: Fix index tuple width estimation in cost model

Summary:
The YB base scans cost model calculates the index tuple width to estimate the
cost of fetching the index from the disk to memory. This change fixes a bug in
the index tuple width calculation.
Jira: DB-10792

Test Plan: ./yb_build.sh --java-test 'org.yb.pgsql.TestPgRegressTAQO#testPgRegressTAQO'

Reviewers: tverona, tnayak

Reviewed By: tnayak

Subscribers: yql

Differential Revision: https://phorge.dev.yugabyte.com/D33947

src/postgres/src/backend/optimizer/path/costsize.c

@@ -6342,7 +6342,8 @@ yb_get_index_tuple_width(IndexOptInfo *index, Oid baserel_oid,
 		/* Aggregate the width of the columns in the secondary index */
 		for (int i = 0; i < index->ncolumns; i++)
 		{
-			index_tuple_width += index->rel->attr_widths[index->indexkeys[i]];
+			index_tuple_width += 
+				index->rel->attr_widths[index->indexkeys[i] - index->rel->min_attr];
 		}
 		index_tuple_width += HIDDEN_COLUMNS_SIZE;
 	}

src/postgres/src/test/regress/expected/yb_planner_taqo_tuning_tests.out

@@ -1218,26 +1218,26 @@ EXPLAIN (COSTS OFF) SELECT * FROM t_range_100k where v1 > 100000;
 
 -- Query Hash: d93f6e4d8c79ed9ff1777a8346135486
 EXPLAIN (COSTS OFF) SELECT v1 FROM t_range_100k where v1 > 0;
-                   QUERY PLAN
-------------------------------------------------
- Index Only Scan using tr100kv1 on t_range_100k
-   Index Cond: (v1 > 0)
+         QUERY PLAN
+----------------------------
+ Seq Scan on t_range_100k
+   Storage Filter: (v1 > 0)
 (2 rows)
 
 -- Query Hash: ad243137d04da666112652bc4daee5bb
 EXPLAIN (COSTS OFF) SELECT v1 FROM t_range_100k where v1 > 1;
-                   QUERY PLAN
-------------------------------------------------
- Index Only Scan using tr100kv1 on t_range_100k
-   Index Cond: (v1 > 1)
+         QUERY PLAN
+----------------------------
+ Seq Scan on t_range_100k
+   Storage Filter: (v1 > 1)
 (2 rows)
 
 -- Query Hash: bfeb69f5dd583f251a20785be7fff7f8
 EXPLAIN (COSTS OFF) SELECT v1 FROM t_range_100k where v1 > 10;
-                   QUERY PLAN
-------------------------------------------------
- Index Only Scan using tr100kv1 on t_range_100k
-   Index Cond: (v1 > 10)
+         QUERY PLAN
+-----------------------------
+ Seq Scan on t_range_100k
+   Storage Filter: (v1 > 10)
 (2 rows)
 
 -- Query Hash: 6c0176a4d1a4d77205315f39efea625c