Improve confusing variable names

The prototype calls the second argument of
pgstat_progress_update_multi_param() "index", and some callers name
their local variable that way.  But when the surrounding code deals
with index relations, this is confusing, and in at least one case
shadowed another variable that is referring to an index relation.
Adjust those call sites to have clearer local variable naming, similar
to existing callers in indexcmds.c.

src/backend/access/nbtree/nbtsort.c

@@ -486,17 +486,17 @@ _bt_spools_heapscan(Relation heap, Relation index, BTBuildState *buildstate,
 	 * values set by table_index_build_scan
 	 */
 	{
-		const int	index[] = {
+		const int	progress_index[] = {
 			PROGRESS_CREATEIDX_TUPLES_TOTAL,
 			PROGRESS_SCAN_BLOCKS_TOTAL,
 			PROGRESS_SCAN_BLOCKS_DONE
 		};
-		const int64 val[] = {
+		const int64 progress_vals[] = {
 			buildstate->indtuples,
 			0, 0
 		};
 
-		pgstat_progress_update_multi_param(3, index, val);
+		pgstat_progress_update_multi_param(3, progress_index, progress_vals);
 	}
 
 	/* okay, all heap tuples are spooled */

src/backend/catalog/index.c

@@ -3045,7 +3045,7 @@ index_build(Relation heapRelation,
 
 	/* Set up initial progress report status */
 	{
-		const int	index[] = {
+		const int	progress_index[] = {
 			PROGRESS_CREATEIDX_PHASE,
 			PROGRESS_CREATEIDX_SUBPHASE,
 			PROGRESS_CREATEIDX_TUPLES_DONE,
@@ -3053,13 +3053,13 @@ index_build(Relation heapRelation,
 			PROGRESS_SCAN_BLOCKS_DONE,
 			PROGRESS_SCAN_BLOCKS_TOTAL
 		};
-		const int64 val[] = {
+		const int64 progress_vals[] = {
 			PROGRESS_CREATEIDX_PHASE_BUILD,
 			PROGRESS_CREATEIDX_SUBPHASE_INITIALIZE,
 			0, 0, 0, 0
 		};
 
-		pgstat_progress_update_multi_param(6, index, val);
+		pgstat_progress_update_multi_param(6, progress_index, progress_vals);
 	}
 
 	/*
@@ -3351,19 +3351,19 @@ validate_index(Oid heapId, Oid indexId, Snapshot snapshot)
 	int			save_nestlevel;
 
 	{
-		const int	index[] = {
+		const int	progress_index[] = {
 			PROGRESS_CREATEIDX_PHASE,
 			PROGRESS_CREATEIDX_TUPLES_DONE,
 			PROGRESS_CREATEIDX_TUPLES_TOTAL,
 			PROGRESS_SCAN_BLOCKS_DONE,
 			PROGRESS_SCAN_BLOCKS_TOTAL
 		};
-		const int64 val[] = {
+		const int64 progress_vals[] = {
 			PROGRESS_CREATEIDX_PHASE_VALIDATE_IDXSCAN,
 			0, 0, 0, 0
 		};
 
-		pgstat_progress_update_multi_param(5, index, val);
+		pgstat_progress_update_multi_param(5, progress_index, progress_vals);
 	}
 
 	/* Open and lock the parent heap relation */
@@ -3420,17 +3420,17 @@ validate_index(Oid heapId, Oid indexId, Snapshot snapshot)
 
 	/* Execute the sort */
 	{
-		const int	index[] = {
+		const int	progress_index[] = {
 			PROGRESS_CREATEIDX_PHASE,
 			PROGRESS_SCAN_BLOCKS_DONE,
 			PROGRESS_SCAN_BLOCKS_TOTAL
 		};
-		const int64 val[] = {
+		const int64 progress_vals[] = {
 			PROGRESS_CREATEIDX_PHASE_VALIDATE_SORT,
 			0, 0
 		};
 
-		pgstat_progress_update_multi_param(3, index, val);
+		pgstat_progress_update_multi_param(3, progress_index, progress_vals);
 	}
 	tuplesort_performsort(state.tuplesort);