Add const decorations

in index.c and indexcmds.c and some adjacent places.  This especially
makes it easier to understand for some complicated function signatures
which are the input and the output arguments.

Discussion: https://www.postgresql.org/message-id/flat/5ed89c69-f4e6-5dab-4003-63bde7460e5e%40eisentraut.org

src/backend/catalog/index.c

@@ -106,20 +106,20 @@ typedef struct
 /* non-export function prototypes */
 static bool relationHasPrimaryKey(Relation rel);
 static TupleDesc ConstructTupleDescriptor(Relation heapRelation,
-										  IndexInfo *indexInfo,
-										  List *indexColNames,
+										  const IndexInfo *indexInfo,
+										  const List *indexColNames,
 										  Oid accessMethodObjectId,
-										  Oid *collationObjectId,
-										  Oid *classObjectId);
+										  const Oid *collationObjectId,
+										  const Oid *classObjectId);
 static void InitializeAttributeOids(Relation indexRelation,
 									int numatts, Oid indexoid);
-static void AppendAttributeTuples(Relation indexRelation, Datum *attopts);
+static void AppendAttributeTuples(Relation indexRelation, const Datum *attopts);
 static void UpdateIndexRelation(Oid indexoid, Oid heapoid,
 								Oid parentIndexId,
-								IndexInfo *indexInfo,
-								Oid *collationOids,
-								Oid *classOids,
-								int16 *coloptions,
+								const IndexInfo *indexInfo,
+								const Oid *collationOids,
+								const Oid *classOids,
+								const int16 *coloptions,
 								bool primary,
 								bool isexclusion,
 								bool immediate,
@@ -205,9 +205,9 @@ relationHasPrimaryKey(Relation rel)
  */
 void
 index_check_primary_key(Relation heapRel,
-						IndexInfo *indexInfo,
+						const IndexInfo *indexInfo,
 						bool is_alter_table,
-						IndexStmt *stmt)
+						const IndexStmt *stmt)
 {
 	int			i;
 
@@ -284,11 +284,11 @@ index_check_primary_key(Relation heapRel,
  */
 static TupleDesc
 ConstructTupleDescriptor(Relation heapRelation,
-						 IndexInfo *indexInfo,
-						 List *indexColNames,
+						 const IndexInfo *indexInfo,
+						 const List *indexColNames,
 						 Oid accessMethodObjectId,
-						 Oid *collationObjectId,
-						 Oid *classObjectId)
+						 const Oid *collationObjectId,
+						 const Oid *classObjectId)
 {
 	int			numatts = indexInfo->ii_NumIndexAttrs;
 	int			numkeyatts = indexInfo->ii_NumIndexKeyAttrs;
@@ -516,7 +516,7 @@ InitializeAttributeOids(Relation indexRelation,
  * ----------------------------------------------------------------
  */
 static void
-AppendAttributeTuples(Relation indexRelation, Datum *attopts)
+AppendAttributeTuples(Relation indexRelation, const Datum *attopts)
 {
 	Relation	pg_attribute;
 	CatalogIndexState indstate;
@@ -551,10 +551,10 @@ static void
 UpdateIndexRelation(Oid indexoid,
 					Oid heapoid,
 					Oid parentIndexId,
-					IndexInfo *indexInfo,
-					Oid *collationOids,
-					Oid *classOids,
-					int16 *coloptions,
+					const IndexInfo *indexInfo,
+					const Oid *collationOids,
+					const Oid *classOids,
+					const int16 *coloptions,
 					bool primary,
 					bool isexclusion,
 					bool immediate,
@@ -718,12 +718,12 @@ index_create(Relation heapRelation,
 			 Oid parentConstraintId,
 			 RelFileNumber relFileNumber,
 			 IndexInfo *indexInfo,
-			 List *indexColNames,
+			 const List *indexColNames,
 			 Oid accessMethodObjectId,
 			 Oid tableSpaceId,
-			 Oid *collationObjectId,
-			 Oid *classObjectId,
-			 int16 *coloptions,
+			 const Oid *collationObjectId,
+			 const Oid *classObjectId,
+			 const int16 *coloptions,
 			 Datum reloptions,
 			 bits16 flags,
 			 bits16 constr_flags,
@@ -1908,7 +1908,7 @@ ObjectAddress
 index_constraint_create(Relation heapRelation,
 						Oid indexRelationId,
 						Oid parentConstraintId,
-						IndexInfo *indexInfo,
+						const IndexInfo *indexInfo,
 						const char *constraintName,
 						char constraintType,
 						bits16 constr_flags,
@@ -2537,10 +2537,10 @@ BuildDummyIndexInfo(Relation index)
  * Use build_attrmap_by_name(index2, index1) to build the attmap.
  */
 bool
-CompareIndexInfo(IndexInfo *info1, IndexInfo *info2,
-				 Oid *collations1, Oid *collations2,
-				 Oid *opfamilies1, Oid *opfamilies2,
-				 AttrMap *attmap)
+CompareIndexInfo(const IndexInfo *info1, const IndexInfo *info2,
+				 const Oid *collations1, const Oid *collations2,
+				 const Oid *opfamilies1, const Oid *opfamilies2,
+				 const AttrMap *attmap)
 {
 	int			i;
 
@@ -3559,7 +3559,7 @@ IndexGetRelation(Oid indexId, bool missing_ok)
  */
 void
 reindex_index(Oid indexId, bool skip_constraint_checks, char persistence,
-			  ReindexParams *params)
+			  const ReindexParams *params)
 {
 	Relation	iRel,
 				heapRelation;
@@ -3872,7 +3872,7 @@ reindex_index(Oid indexId, bool skip_constraint_checks, char persistence,
  * index rebuild.
  */
 bool
-reindex_relation(Oid relid, int flags, ReindexParams *params)
+reindex_relation(Oid relid, int flags, const ReindexParams *params)
 {
 	Relation	rel;
 	Oid			toast_relid;
@@ -4177,9 +4177,9 @@ SerializeReindexState(Size maxsize, char *start_address)
  *		Restore reindex state in a parallel worker.
  */
 void
-RestoreReindexState(void *reindexstate)
+RestoreReindexState(const void *reindexstate)
 {
-	SerializedReindexState *sistate = (SerializedReindexState *) reindexstate;
+	const SerializedReindexState *sistate = (const SerializedReindexState *) reindexstate;
 	int			c = 0;
 	MemoryContext oldcontext;