Mark function arguments of type "Datum *" as "const Datum *" where possible

Several functions in the codebase accept "Datum *" parameters but do
not modify the pointed-to data.  These have been updated to take
"const Datum *" instead, improving type safety and making the
interfaces clearer about their intent.  This change helps the compiler
catch accidental modifications and better documents immutability of
arguments.

Most of "Datum *" parameters have a pairing "bool *isnull" parameter,
they are constified as well.

No functional behavior is changed by this patch.

Author: Chao Li <lic@highgo.com>
Discussion: https://www.postgresql.org/message-id/flat/CAEoWx2msfT0knvzUa72ZBwu9LR_RLY4on85w2a9YpE-o2By5HQ@mail.gmail.com

1 files changed, 24 insertions, 24 deletions

diff --git a/src/backend/utils/adt/array_selfuncs.c b/src/backend/utils/adt/array_selfuncs.c
index cf6fbf8652c..4dab35b0057 100644
--- a/src/backend/utils/adt/array_selfuncs.c
+++ b/src/backend/utils/adt/array_selfuncs.c
@@ -39,25 +39,25 @@
 
 static Selectivity calc_arraycontsel(VariableStatData *vardata, Datum constval,
 									 Oid elemtype, Oid operator);
-static Selectivity mcelem_array_selec(ArrayType *array,
+static Selectivity mcelem_array_selec(const ArrayType *array,
 									  TypeCacheEntry *typentry,
-									  Datum *mcelem, int nmcelem,
-									  float4 *numbers, int nnumbers,
-									  float4 *hist, int nhist,
+									  const Datum *mcelem, int nmcelem,
+									  const float4 *numbers, int nnumbers,
+									  const float4 *hist, int nhist,
 									  Oid operator);
-static Selectivity mcelem_array_contain_overlap_selec(Datum *mcelem, int nmcelem,
-													  float4 *numbers, int nnumbers,
-													  Datum *array_data, int nitems,
+static Selectivity mcelem_array_contain_overlap_selec(const Datum *mcelem, int nmcelem,
+													  const float4 *numbers, int nnumbers,
+													  const Datum *array_data, int nitems,
 													  Oid operator, TypeCacheEntry *typentry);
-static Selectivity mcelem_array_contained_selec(Datum *mcelem, int nmcelem,
-												float4 *numbers, int nnumbers,
-												Datum *array_data, int nitems,
-												float4 *hist, int nhist,
+static Selectivity mcelem_array_contained_selec(const Datum *mcelem, int nmcelem,
+												const float4 *numbers, int nnumbers,
+												const Datum *array_data, int nitems,
+												const float4 *hist, int nhist,
 												Oid operator, TypeCacheEntry *typentry);
 static float *calc_hist(const float4 *hist, int nhist, int n);
 static float *calc_distr(const float *p, int n, int m, float rest);
 static int	floor_log2(uint32 n);
-static bool find_next_mcelem(Datum *mcelem, int nmcelem, Datum value,
+static bool find_next_mcelem(const Datum *mcelem, int nmcelem, Datum value,
 							 int *index, TypeCacheEntry *typentry);
 static int	element_compare(const void *key1, const void *key2, void *arg);
 static int	float_compare_desc(const void *key1, const void *key2);
@@ -425,10 +425,10 @@ calc_arraycontsel(VariableStatData *vardata, Datum constval,
  * mcelem_array_contained_selec depending on the operator.
  */
 static Selectivity
-mcelem_array_selec(ArrayType *array, TypeCacheEntry *typentry,
-				   Datum *mcelem, int nmcelem,
-				   float4 *numbers, int nnumbers,
-				   float4 *hist, int nhist,
+mcelem_array_selec(const ArrayType *array, TypeCacheEntry *typentry,
+				   const Datum *mcelem, int nmcelem,
+				   const float4 *numbers, int nnumbers,
+				   const float4 *hist, int nhist,
 				   Oid operator)
 {
 	Selectivity selec;
@@ -518,9 +518,9 @@ mcelem_array_selec(ArrayType *array, TypeCacheEntry *typentry,
  * fraction of nonempty arrays in the column.
  */
 static Selectivity
-mcelem_array_contain_overlap_selec(Datum *mcelem, int nmcelem,
-								   float4 *numbers, int nnumbers,
-								   Datum *array_data, int nitems,
+mcelem_array_contain_overlap_selec(const Datum *mcelem, int nmcelem,
+								   const float4 *numbers, int nnumbers,
+								   const Datum *array_data, int nitems,
 								   Oid operator, TypeCacheEntry *typentry)
 {
 	Selectivity selec,
@@ -699,10 +699,10 @@ mcelem_array_contain_overlap_selec(Datum *mcelem, int nmcelem,
  * ... * fn^on * (1 - fn)^(1 - on), o1, o2, ..., on) | o1 + o2 + .. on = m
  */
 static Selectivity
-mcelem_array_contained_selec(Datum *mcelem, int nmcelem,
-							 float4 *numbers, int nnumbers,
-							 Datum *array_data, int nitems,
-							 float4 *hist, int nhist,
+mcelem_array_contained_selec(const Datum *mcelem, int nmcelem,
+							 const float4 *numbers, int nnumbers,
+							 const Datum *array_data, int nitems,
+							 const float4 *hist, int nhist,
 							 Oid operator, TypeCacheEntry *typentry)
 {
 	int			mcelem_index,
@@ -1136,7 +1136,7 @@ floor_log2(uint32 n)
  * exact match.)
  */
 static bool
-find_next_mcelem(Datum *mcelem, int nmcelem, Datum value, int *index,
+find_next_mcelem(const Datum *mcelem, int nmcelem, Datum value, int *index,
 				 TypeCacheEntry *typentry)
 {
 	int			l = *index,