Make Bitmapsets be valid Nodes.

Add a NodeTag field to struct Bitmapset.  This is free because of
alignment considerations on 64-bit hardware.  While it adds some
space on 32-bit machines, we aren't optimizing for that case anymore.
The advantage is that data structures such as Lists of Bitmapsets
are now first-class objects to the Node infrastructure, and don't
require special-case code to handle.

This patch includes removal of one such special case, in indxpath.c:
bms_equal_any() can now be replaced by list_member().  There may be
more existing code that could be simplified, but I didn't look very
hard.  We also get to drop the read_write_ignore annotations on a
couple of RelOptInfo fields.

The outfuncs/readfuncs support is arranged so that nothing changes
in the string representation of a Bitmapset field; therefore, this
doesn't need a catversion bump.

Amit Langote and Tom Lane

Discussion: https://postgr.es/m/109089.1668197158@sss.pgh.pa.us

src/backend/nodes/Makefile

@@ -52,6 +52,7 @@ node_headers = \
 	commands/trigger.h \
 	executor/tuptable.h \
 	foreign/fdwapi.h \
+	nodes/bitmapset.h \
 	nodes/extensible.h \
 	nodes/lockoptions.h \
 	nodes/replnodes.h \

src/backend/nodes/bitmapset.c

@@ -194,6 +194,7 @@ bms_make_singleton(int x)
 	wordnum = WORDNUM(x);
 	bitnum = BITNUM(x);
 	result = (Bitmapset *) palloc0(BITMAPSET_SIZE(wordnum + 1));
+	result->type = T_Bitmapset;
 	result->nwords = wordnum + 1;
 	result->words[wordnum] = ((bitmapword) 1 << bitnum);
 	return result;
@@ -852,6 +853,7 @@ bms_add_range(Bitmapset *a, int lower, int upper)
 	if (a == NULL)
 	{
 		a = (Bitmapset *) palloc0(BITMAPSET_SIZE(uwordnum + 1));
+		a->type = T_Bitmapset;
 		a->nwords = uwordnum + 1;
 	}
 	else if (uwordnum >= a->nwords)

src/backend/nodes/copyfuncs.c

@@ -160,6 +160,12 @@ _copyExtensibleNode(const ExtensibleNode *from)
 	return newnode;
 }
 
+static Bitmapset *
+_copyBitmapset(const Bitmapset *from)
+{
+	return bms_copy(from);
+}
+
 
 /*
  * copyObjectImpl -- implementation of copyObject(); see nodes/nodes.h

src/backend/nodes/equalfuncs.c

@@ -145,6 +145,12 @@ _equalA_Const(const A_Const *a, const A_Const *b)
 	return true;
 }
 
+static bool
+_equalBitmapset(const Bitmapset *a, const Bitmapset *b)
+{
+	return bms_equal(a, b);
+}
+
 /*
  * Lists are handled specially
  */

src/backend/nodes/gen_node_support.pl

@@ -65,6 +65,7 @@ my @all_input_files = qw(
   commands/trigger.h
   executor/tuptable.h
   foreign/fdwapi.h
+  nodes/bitmapset.h
   nodes/extensible.h
   nodes/lockoptions.h
   nodes/replnodes.h

src/backend/nodes/outfuncs.c

@@ -314,6 +314,9 @@ _outList(StringInfo str, const List *node)
  *	   converts a bitmap set of integers
  *
  * Note: the output format is "(b int int ...)", similar to an integer List.
+ *
+ * We export this function for use by extensions that define extensible nodes.
+ * That's somewhat historical, though, because calling outNode() will work.
  */
 void
 outBitmapset(StringInfo str, const Bitmapset *bms)
@@ -844,6 +847,8 @@ outNode(StringInfo str, const void *obj)
 		_outString(str, (String *) obj);
 	else if (IsA(obj, BitString))
 		_outBitString(str, (BitString *) obj);
+	else if (IsA(obj, Bitmapset))
+		outBitmapset(str, (Bitmapset *) obj);
 	else
 	{
 		appendStringInfoChar(str, '{');

src/backend/nodes/read.c

@@ -22,6 +22,7 @@
 #include <ctype.h>
 
 #include "common/string.h"
+#include "nodes/bitmapset.h"
 #include "nodes/pg_list.h"
 #include "nodes/readfuncs.h"
 #include "nodes/value.h"
@@ -347,6 +348,7 @@ nodeRead(const char *token, int tok_len)
 				 * Could be an integer list:	(i int int ...)
 				 * or an OID list:				(o int int ...)
 				 * or an XID list:				(x int int ...)
+				 * or a bitmapset:				(b int int ...)
 				 * or a list of nodes/values:	(node node ...)
 				 *----------
 				 */
@@ -372,6 +374,7 @@ nodeRead(const char *token, int tok_len)
 								 tok_len, token);
 						l = lappend_int(l, val);
 					}
+					result = (Node *) l;
 				}
 				else if (tok_len == 1 && token[0] == 'o')
 				{
@@ -392,6 +395,7 @@ nodeRead(const char *token, int tok_len)
 								 tok_len, token);
 						l = lappend_oid(l, val);
 					}
+					result = (Node *) l;
 				}
 				else if (tok_len == 1 && token[0] == 'x')
 				{
@@ -412,6 +416,30 @@ nodeRead(const char *token, int tok_len)
 								 tok_len, token);
 						l = lappend_xid(l, val);
 					}
+					result = (Node *) l;
+				}
+				else if (tok_len == 1 && token[0] == 'b')
+				{
+					/* Bitmapset -- see also _readBitmapset() */
+					Bitmapset  *bms = NULL;
+
+					for (;;)
+					{
+						int			val;
+						char	   *endptr;
+
+						token = pg_strtok(&tok_len);
+						if (token == NULL)
+							elog(ERROR, "unterminated Bitmapset structure");
+						if (tok_len == 1 && token[0] == ')')
+							break;
+						val = (int) strtol(token, &endptr, 10);
+						if (endptr != token + tok_len)
+							elog(ERROR, "unrecognized integer: \"%.*s\"",
+								 tok_len, token);
+						bms = bms_add_member(bms, val);
+					}
+					result = (Node *) bms;
 				}
 				else
 				{
@@ -426,8 +454,8 @@ nodeRead(const char *token, int tok_len)
 						if (token == NULL)
 							elog(ERROR, "unterminated List structure");
 					}
+					result = (Node *) l;
 				}
-				result = (Node *) l;
 				break;
 			}
 		case RIGHT_PAREN:

src/backend/nodes/readfuncs.c

@@ -194,6 +194,10 @@ nullable_string(const char *token, int length)
 
 /*
  * _readBitmapset
+ *
+ * Note: this code is used in contexts where we know that a Bitmapset
+ * is expected.  There is equivalent code in nodeRead() that can read a
+ * Bitmapset when we come across one in other contexts.
  */
 static Bitmapset *
 _readBitmapset(void)
@@ -234,7 +238,8 @@ _readBitmapset(void)
 }
 
 /*
- * for use by extensions which define extensible nodes
+ * We export this function for use by extensions that define extensible nodes.
+ * That's somewhat historical, though, because calling nodeRead() will work.
  */
 Bitmapset *
 readBitmapset(void)

src/backend/optimizer/path/indxpath.c

@@ -99,7 +99,6 @@ static void get_join_index_paths(PlannerInfo *root, RelOptInfo *rel,
 								 List **considered_relids);
 static bool eclass_already_used(EquivalenceClass *parent_ec, Relids oldrelids,
 								List *indexjoinclauses);
-static bool bms_equal_any(Relids relids, List *relids_list);
 static void get_index_paths(PlannerInfo *root, RelOptInfo *rel,
 							IndexOptInfo *index, IndexClauseSet *clauses,
 							List **bitindexpaths);
@@ -370,8 +369,8 @@ create_index_paths(PlannerInfo *root, RelOptInfo *rel)
 			Path	   *path = (Path *) lfirst(lc);
 			Relids		required_outer = PATH_REQ_OUTER(path);
 
-			if (!bms_equal_any(required_outer, all_path_outers))
+			all_path_outers = list_append_unique(all_path_outers,
-				all_path_outers = lappend(all_path_outers, required_outer);
+												 required_outer);
 		}
 
 		/* Now, for each distinct parameterization set ... */
@@ -517,7 +516,7 @@ consider_index_join_outer_rels(PlannerInfo *root, RelOptInfo *rel,
 		int			num_considered_relids;
 
 		/* If we already tried its relids set, no need to do so again */
-		if (bms_equal_any(clause_relids, *considered_relids))
+		if (list_member(*considered_relids, clause_relids))
 			continue;
 
 		/*
@@ -612,7 +611,7 @@ get_join_index_paths(PlannerInfo *root, RelOptInfo *rel,
 	int			indexcol;
 
 	/* If we already considered this relids set, don't repeat the work */
-	if (bms_equal_any(relids, *considered_relids))
+	if (list_member(*considered_relids, relids))
 		return;
 
 	/* Identify indexclauses usable with this relids set */
@@ -694,25 +693,6 @@ eclass_already_used(EquivalenceClass *parent_ec, Relids oldrelids,
 	return false;
 }
 
-/*
- * bms_equal_any
- *		True if relids is bms_equal to any member of relids_list
- *
- * Perhaps this should be in bitmapset.c someday.
- */
-static bool
-bms_equal_any(Relids relids, List *relids_list)
-{
-	ListCell   *lc;
-
-	foreach(lc, relids_list)
-	{
-		if (bms_equal(relids, (Relids) lfirst(lc)))
-			return true;
-	}
-	return false;
-}
-
 
 /*
  * get_index_paths

src/include/nodes/bitmapset.h

@@ -20,6 +20,8 @@
 #ifndef BITMAPSET_H
 #define BITMAPSET_H
 
+#include "nodes/nodes.h"
+
 /*
  * Forward decl to save including pg_list.h
  */
@@ -48,6 +50,9 @@ typedef int32 signedbitmapword; /* must be the matching signed type */
 
 typedef struct Bitmapset
 {
+	pg_node_attr(custom_copy_equal, special_read_write)
+
+	NodeTag		type;
 	int			nwords;			/* number of words in array */
 	bitmapword	words[FLEXIBLE_ARRAY_MEMBER];	/* really [nwords] */
 } Bitmapset;

src/include/nodes/meson.build

@@ -13,6 +13,7 @@ node_support_input_i = [
   'commands/trigger.h',
   'executor/tuptable.h',
   'foreign/fdwapi.h',
+  'nodes/bitmapset.h',
   'nodes/extensible.h',
   'nodes/lockoptions.h',
   'nodes/replnodes.h',

src/include/nodes/pathnodes.h

@@ -911,13 +911,11 @@ typedef struct RelOptInfo
 
 	/*
 	 * cache space for remembering if we have proven this relation unique
-	 *
-	 * can't print unique_for_rels/non_unique_for_rels; BMSes aren't Nodes
 	 */
 	/* known unique for these other relid set(s) */
-	List	   *unique_for_rels pg_node_attr(read_write_ignore);
+	List	   *unique_for_rels;
 	/* known not unique for these set(s) */
-	List	   *non_unique_for_rels pg_node_attr(read_write_ignore);
+	List	   *non_unique_for_rels;
 
 	/*
 	 * used by various scans and joins: