Move code specific to pg_dependencies to new file

This new file is named pg_dependencies.c and includes all the code
directly related to the data type pg_dependencies, extracted from the
extended statistics code.

Some patches are under discussion to change its input and output
functions, and this separation makes the follow-up changes cleaner by
separating the logic related to the data type and the functional
dependencies statistics core logic in dependencies.c.

Author: Corey Huinker <corey.huinker@gmail.com>
Co-authored-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/aQ2k8--a0FfwSwX9@paquier.xyz

src/backend/statistics/dependencies.c

@@ -16,23 +16,17 @@
 #include "access/htup_details.h"
 #include "catalog/pg_statistic_ext.h"
 #include "catalog/pg_statistic_ext_data.h"
-#include "lib/stringinfo.h"
 #include "nodes/nodeFuncs.h"
-#include "nodes/nodes.h"
-#include "nodes/pathnodes.h"
 #include "optimizer/clauses.h"
 #include "optimizer/optimizer.h"
 #include "parser/parsetree.h"
 #include "statistics/extended_stats_internal.h"
-#include "statistics/statistics.h"
 #include "utils/fmgroids.h"
-#include "utils/fmgrprotos.h"
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/selfuncs.h"
 #include "utils/syscache.h"
 #include "utils/typcache.h"
-#include "varatt.h"
 
 /* size of the struct header fields (magic, type, ndeps) */
 #define SizeOfHeader		(3 * sizeof(uint32))
@@ -643,91 +637,6 @@ statext_dependencies_load(Oid mvoid, bool inh)
 	return result;
 }
 
-/*
- * pg_dependencies_in		- input routine for type pg_dependencies.
- *
- * pg_dependencies is real enough to be a table column, but it has no operations
- * of its own, and disallows input too
- */
-Datum
-pg_dependencies_in(PG_FUNCTION_ARGS)
-{
-	/*
-	 * pg_node_list stores the data in binary form and parsing text input is
-	 * not needed, so disallow this.
-	 */
-	ereport(ERROR,
-			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-			 errmsg("cannot accept a value of type %s", "pg_dependencies")));
-
-	PG_RETURN_VOID();			/* keep compiler quiet */
-}
-
-/*
- * pg_dependencies		- output routine for type pg_dependencies.
- */
-Datum
-pg_dependencies_out(PG_FUNCTION_ARGS)
-{
-	bytea	   *data = PG_GETARG_BYTEA_PP(0);
-	MVDependencies *dependencies = statext_dependencies_deserialize(data);
-	int			i,
-				j;
-	StringInfoData str;
-
-	initStringInfo(&str);
-	appendStringInfoChar(&str, '{');
-
-	for (i = 0; i < dependencies->ndeps; i++)
-	{
-		MVDependency *dependency = dependencies->deps[i];
-
-		if (i > 0)
-			appendStringInfoString(&str, ", ");
-
-		appendStringInfoChar(&str, '"');
-		for (j = 0; j < dependency->nattributes; j++)
-		{
-			if (j == dependency->nattributes - 1)
-				appendStringInfoString(&str, " => ");
-			else if (j > 0)
-				appendStringInfoString(&str, ", ");
-
-			appendStringInfo(&str, "%d", dependency->attributes[j]);
-		}
-		appendStringInfo(&str, "\": %f", dependency->degree);
-	}
-
-	appendStringInfoChar(&str, '}');
-
-	PG_RETURN_CSTRING(str.data);
-}
-
-/*
- * pg_dependencies_recv		- binary input routine for type pg_dependencies.
- */
-Datum
-pg_dependencies_recv(PG_FUNCTION_ARGS)
-{
-	ereport(ERROR,
-			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-			 errmsg("cannot accept a value of type %s", "pg_dependencies")));
-
-	PG_RETURN_VOID();			/* keep compiler quiet */
-}
-
-/*
- * pg_dependencies_send		- binary output routine for type pg_dependencies.
- *
- * Functional dependencies are serialized in a bytea value (although the type
- * is named differently), so let's just send that.
- */
-Datum
-pg_dependencies_send(PG_FUNCTION_ARGS)
-{
-	return byteasend(fcinfo);
-}
-
 /*
  * dependency_is_compatible_clause
  *		Determines if the clause is compatible with functional dependencies

src/backend/utils/adt/Makefile

@@ -80,6 +80,7 @@ OBJS = \
 	oracle_compat.o \
 	orderedsetaggs.o \
 	partitionfuncs.o \
+	pg_dependencies.o \
 	pg_locale.o \
 	pg_locale_builtin.o \
 	pg_locale_icu.o \

src/backend/utils/adt/meson.build

@@ -76,6 +76,7 @@ backend_sources += files(
   'oracle_compat.c',
   'orderedsetaggs.c',
   'partitionfuncs.c',
+  'pg_dependencies.c',
   'pg_locale.c',
   'pg_locale_builtin.c',
   'pg_locale_icu.c',

src/backend/utils/adt/pg_dependencies.c

@@ -0,0 +1,104 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_dependencies.c
+ *		pg_dependencies data type support.
+ *
+ * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/adt/pg_dependencies.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "lib/stringinfo.h"
+#include "statistics/extended_stats_internal.h"
+#include "utils/fmgrprotos.h"
+
+/*
+ * pg_dependencies_in		- input routine for type pg_dependencies.
+ *
+ * pg_dependencies is real enough to be a table column, but it has no operations
+ * of its own, and disallows input too
+ */
+Datum
+pg_dependencies_in(PG_FUNCTION_ARGS)
+{
+	/*
+	 * pg_node_list stores the data in binary form and parsing text input is
+	 * not needed, so disallow this.
+	 */
+	ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("cannot accept a value of type %s", "pg_dependencies")));
+
+	PG_RETURN_VOID();			/* keep compiler quiet */
+}
+
+/*
+ * pg_dependencies		- output routine for type pg_dependencies.
+ */
+Datum
+pg_dependencies_out(PG_FUNCTION_ARGS)
+{
+	bytea	   *data = PG_GETARG_BYTEA_PP(0);
+	MVDependencies *dependencies = statext_dependencies_deserialize(data);
+	int			i,
+				j;
+	StringInfoData str;
+
+	initStringInfo(&str);
+	appendStringInfoChar(&str, '{');
+
+	for (i = 0; i < dependencies->ndeps; i++)
+	{
+		MVDependency *dependency = dependencies->deps[i];
+
+		if (i > 0)
+			appendStringInfoString(&str, ", ");
+
+		appendStringInfoChar(&str, '"');
+		for (j = 0; j < dependency->nattributes; j++)
+		{
+			if (j == dependency->nattributes - 1)
+				appendStringInfoString(&str, " => ");
+			else if (j > 0)
+				appendStringInfoString(&str, ", ");
+
+			appendStringInfo(&str, "%d", dependency->attributes[j]);
+		}
+		appendStringInfo(&str, "\": %f", dependency->degree);
+	}
+
+	appendStringInfoChar(&str, '}');
+
+	PG_RETURN_CSTRING(str.data);
+}
+
+/*
+ * pg_dependencies_recv		- binary input routine for type pg_dependencies.
+ */
+Datum
+pg_dependencies_recv(PG_FUNCTION_ARGS)
+{
+	ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("cannot accept a value of type %s", "pg_dependencies")));
+
+	PG_RETURN_VOID();			/* keep compiler quiet */
+}
+
+/*
+ * pg_dependencies_send		- binary output routine for type pg_dependencies.
+ *
+ * Functional dependencies are serialized in a bytea value (although the type
+ * is named differently), so let's just send that.
+ */
+Datum
+pg_dependencies_send(PG_FUNCTION_ARGS)
+{
+	return byteasend(fcinfo);
+}