Remove no-op GiST support functions in the core GiST opclasses.

The preceding patch allowed us to remove useless GiST support functions.
This patch actually does that for all the no-op cases in the core GiST
code.  This buys us whatever performance gain is to be had, and more
importantly exercises the preceding patch.

There remain no-op functions in the contrib GiST opclasses, but those
will take more work to remove.

Discussion: https://postgr.es/m/CAJEAwVELVx9gYscpE=Be6iJxvdW5unZ_LkcAaVNSeOwvdwtD=A@mail.gmail.com

4 files changed, 15 insertions, 39 deletions

diff --git a/src/backend/utils/adt/network_gist.c b/src/backend/utils/adt/network_gist.c
index a0097dae9c5..0e36b7685de 100644
--- a/src/backend/utils/adt/network_gist.c
+++ b/src/backend/utils/adt/network_gist.c
@@ -576,17 +576,9 @@ inet_gist_compress(PG_FUNCTION_ARGS)
 }
 
 /*
- * The GiST decompress function
- *
- * do not do anything --- we just use the stored GistInetKey as-is.
+ * We do not need a decompress function, because the other GiST inet
+ * support functions work with the GistInetKey representation.
  */
-Datum
-inet_gist_decompress(PG_FUNCTION_ARGS)
-{
-	GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
-
-	PG_RETURN_POINTER(entry);
-}
 
 /*
  * The GiST fetch function
diff --git a/src/backend/utils/adt/rangetypes_gist.c b/src/backend/utils/adt/rangetypes_gist.c
index cb2d5a3b73a..29fa1ae325b 100644
--- a/src/backend/utils/adt/rangetypes_gist.c
+++ b/src/backend/utils/adt/rangetypes_gist.c
@@ -216,30 +216,11 @@ range_gist_union(PG_FUNCTION_ARGS)
 	PG_RETURN_RANGE_P(result_range);
 }
 
-/* compress, decompress, fetch are no-ops */
-Datum
-range_gist_compress(PG_FUNCTION_ARGS)
-{
-	GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
-
-	PG_RETURN_POINTER(entry);
-}
-
-Datum
-range_gist_decompress(PG_FUNCTION_ARGS)
-{
-	GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
-
-	PG_RETURN_POINTER(entry);
-}
-
-Datum
-range_gist_fetch(PG_FUNCTION_ARGS)
-{
-	GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
-
-	PG_RETURN_POINTER(entry);
-}
+/*
+ * We store ranges as ranges in GiST indexes, so we do not need
+ * compress, decompress, or fetch functions.  Note this implies a limit
+ * on the size of range values that can be indexed.
+ */
 
 /*
  * GiST page split penalty function.
diff --git a/src/backend/utils/adt/tsgistidx.c b/src/backend/utils/adt/tsgistidx.c
index 732d87f22ff..578af5d5126 100644
--- a/src/backend/utils/adt/tsgistidx.c
+++ b/src/backend/utils/adt/tsgistidx.c
@@ -272,6 +272,10 @@ gtsvector_compress(PG_FUNCTION_ARGS)
 Datum
 gtsvector_decompress(PG_FUNCTION_ARGS)
 {
+	/*
+	 * We need to detoast the stored value, because the other gtsvector
+	 * support functions don't cope with toasted values.
+	 */
 	GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
 	SignTSVector *key = (SignTSVector *) PG_DETOAST_DATUM(entry->key);
 
diff --git a/src/backend/utils/adt/tsquery_gist.c b/src/backend/utils/adt/tsquery_gist.c
index 85518dc7d9f..05bc0d6adb3 100644
--- a/src/backend/utils/adt/tsquery_gist.c
+++ b/src/backend/utils/adt/tsquery_gist.c
@@ -43,11 +43,10 @@ gtsquery_compress(PG_FUNCTION_ARGS)
 	PG_RETURN_POINTER(retval);
 }
 
-Datum
-gtsquery_decompress(PG_FUNCTION_ARGS)
-{
-	PG_RETURN_DATUM(PG_GETARG_DATUM(0));
-}
+/*
+ * We do not need a decompress function, because the other gtsquery
+ * support functions work with the compressed representation.
+ */
 
 Datum
 gtsquery_consistent(PG_FUNCTION_ARGS)