Add COMMENT ON CONSTRAINT facility (from Rod Taylor's pg_constraint patch).

Fix comment.c to not depend on parser token values, per discussion awhile
back.

src/backend/commands/comment.c

@@ -7,7 +7,7 @@
  * Copyright (c) 1996-2001, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/comment.c,v 1.50 2002/07/12 18:43:15 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/comment.c,v 1.51 2002/07/14 23:38:13 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -19,6 +19,7 @@
 #include "catalog/catname.h"
 #include "catalog/indexing.h"
 #include "catalog/namespace.h"
+#include "catalog/pg_constraint.h"
 #include "catalog/pg_database.h"
 #include "catalog/pg_description.h"
 #include "catalog/pg_namespace.h"
@@ -30,7 +31,6 @@
 #include "parser/parse_func.h"
 #include "parser/parse_oper.h"
 #include "parser/parse_type.h"
-#include "parser/parse.h"
 #include "utils/acl.h"
 #include "utils/builtins.h"
 #include "utils/fmgroids.h"
@@ -57,6 +57,7 @@ static void CommentAggregate(List *aggregate, List *arguments, char *comment);
 static void CommentProc(List *function, List *arguments, char *comment);
 static void CommentOperator(List *opername, List *arguments, char *comment);
 static void CommentTrigger(List *qualname, char *comment);
+static void CommentConstraint(List *qualname, char *comment);
 
 
 /*
@@ -70,39 +71,42 @@ CommentObject(CommentStmt *stmt)
 {
 	switch (stmt->objtype)
 	{
-		case INDEX:
-		case SEQUENCE:
-		case TABLE:
-		case VIEW:
+		case COMMENT_ON_INDEX:
+		case COMMENT_ON_SEQUENCE:
+		case COMMENT_ON_TABLE:
+		case COMMENT_ON_VIEW:
 			CommentRelation(stmt->objtype, stmt->objname, stmt->comment);
 			break;
-		case COLUMN:
+		case COMMENT_ON_COLUMN:
 			CommentAttribute(stmt->objname, stmt->comment);
 			break;
-		case DATABASE:
+		case COMMENT_ON_DATABASE:
 			CommentDatabase(stmt->objname, stmt->comment);
 			break;
-		case RULE:
+		case COMMENT_ON_RULE:
 			CommentRule(stmt->objname, stmt->comment);
 			break;
-		case TYPE_P:
+		case COMMENT_ON_TYPE:
 			CommentType(stmt->objname, stmt->comment);
 			break;
-		case AGGREGATE:
+		case COMMENT_ON_AGGREGATE:
 			CommentAggregate(stmt->objname, stmt->objargs, stmt->comment);
 			break;
-		case FUNCTION:
+		case COMMENT_ON_FUNCTION:
 			CommentProc(stmt->objname, stmt->objargs, stmt->comment);
 			break;
-		case OPERATOR:
+		case COMMENT_ON_OPERATOR:
 			CommentOperator(stmt->objname, stmt->objargs, stmt->comment);
 			break;
-		case TRIGGER:
+		case COMMENT_ON_TRIGGER:
 			CommentTrigger(stmt->objname, stmt->comment);
 			break;
-		case SCHEMA:
+		case COMMENT_ON_SCHEMA:
 			CommentNamespace(stmt->objname, stmt->comment);
 			break;
+		case COMMENT_ON_CONSTRAINT:
+			CommentConstraint(stmt->objname, stmt->comment);
+			break;
 		default:
 			elog(ERROR, "An attempt was made to comment on a unknown type: %d",
 				 stmt->objtype);
@@ -309,26 +313,26 @@ CommentRelation(int objtype, List *relname, char *comment)
 
 	switch (objtype)
 	{
-		case INDEX:
+		case COMMENT_ON_INDEX:
 			if (relation->rd_rel->relkind != RELKIND_INDEX)
 				elog(ERROR, "relation \"%s\" is not an index",
 					 RelationGetRelationName(relation));
 			break;
-		case TABLE:
+		case COMMENT_ON_SEQUENCE:
+			if (relation->rd_rel->relkind != RELKIND_SEQUENCE)
+				elog(ERROR, "relation \"%s\" is not a sequence",
+					 RelationGetRelationName(relation));
+			break;
+		case COMMENT_ON_TABLE:
 			if (relation->rd_rel->relkind != RELKIND_RELATION)
 				elog(ERROR, "relation \"%s\" is not a table",
 					 RelationGetRelationName(relation));
 			break;
-		case VIEW:
+		case COMMENT_ON_VIEW:
 			if (relation->rd_rel->relkind != RELKIND_VIEW)
 				elog(ERROR, "relation \"%s\" is not a view",
 					 RelationGetRelationName(relation));
 			break;
-		case SEQUENCE:
-			if (relation->rd_rel->relkind != RELKIND_SEQUENCE)
-				elog(ERROR, "relation \"%s\" is not a sequence",
-					 RelationGetRelationName(relation));
-			break;
 	}
 
 	/* Create the comment using the relation's oid */
@@ -439,7 +443,7 @@ CommentDatabase(List *qualname, char *comment)
 		elog(ERROR, "you are not permitted to comment on database \"%s\"",
 			 database);
 
-	/* Create the comments with the pg_database oid */
+	/* Create the comment with the pg_database oid */
 
 	CreateComments(oid, RelOid_pg_database, 0, comment);
 
@@ -805,7 +809,7 @@ CommentTrigger(List *qualname, char *comment)
 
 	systable_endscan(scan);
 
-	/* Create the comments with the pg_trigger oid */
+	/* Create the comment with the pg_trigger oid */
 
 	CreateComments(oid, RelationGetRelid(pg_trigger), 0, comment);
 
@@ -814,3 +818,83 @@ CommentTrigger(List *qualname, char *comment)
 	heap_close(pg_trigger, AccessShareLock);
 	heap_close(relation, NoLock);
 }
+
+
+/*
+ * CommentConstraint --
+ *
+ * Enable commenting on constraints held within the pg_constraint
+ * table.  A qualified name is required as constraint names are
+ * unique per relation.
+ */
+static void
+CommentConstraint(List *qualname, char *comment)
+{
+	int			nnames;
+	List	   *relName;
+	char	   *conName;
+	RangeVar   *rel;
+	Relation	pg_constraint,
+				relation;
+	HeapTuple	tuple;
+	SysScanDesc	scan;
+	ScanKeyData skey[1];
+	Oid			conOid = InvalidOid;
+
+	/* Separate relname and constraint name */
+	nnames = length(qualname);
+	if (nnames < 2)
+		elog(ERROR, "CommentConstraint: must specify relation and constraint");
+	relName = ltruncate(nnames-1, listCopy(qualname));
+	conName = strVal(nth(nnames-1, qualname));
+
+	/* Open the owning relation to ensure it won't go away meanwhile */
+	rel = makeRangeVarFromNameList(relName);
+	relation = heap_openrv(rel, AccessShareLock);
+
+	/* Check object security */
+
+	if (!pg_class_ownercheck(RelationGetRelid(relation), GetUserId()))
+		aclcheck_error(ACLCHECK_NOT_OWNER, RelationGetRelationName(relation));
+
+	/*
+	 * Fetch the constraint tuple from pg_constraint.  There may be more than
+	 * one match, because constraints are not required to have unique names;
+	 * if so, error out.
+	 */
+	pg_constraint = heap_openr(ConstraintRelationName, AccessShareLock);
+
+	ScanKeyEntryInitialize(&skey[0], 0x0,
+						   Anum_pg_constraint_conrelid, F_OIDEQ,
+						   ObjectIdGetDatum(RelationGetRelid(relation)));
+
+	scan = systable_beginscan(pg_constraint, ConstraintRelidIndex, true,
+							  SnapshotNow, 1, skey);
+
+	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
+	{
+		Form_pg_constraint	con = (Form_pg_constraint) GETSTRUCT(tuple);
+
+		if (strcmp(NameStr(con->conname), conName) == 0)
+		{
+			if (OidIsValid(conOid))
+				elog(ERROR, "Relation \"%s\" has multiple constraints named \"%s\"",
+					 RelationGetRelationName(relation), conName);
+			conOid = tuple->t_data->t_oid;
+		}
+	}
+
+	systable_endscan(scan);
+
+	/* If no constraint exists for the relation specified, notify user */
+	if (!OidIsValid(conOid))
+		elog(ERROR, "constraint \"%s\" for relation \"%s\" does not exist",
+			 conName, RelationGetRelationName(relation));
+
+	/* Create the comment with the pg_constraint oid */
+	CreateComments(conOid, RelationGetRelid(pg_constraint), 0, comment);
+
+	/* Done, but hold lock on relation */
+	heap_close(pg_constraint, AccessShareLock);
+	heap_close(relation, NoLock);
+}

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.339 2002/07/12 18:43:17 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.340 2002/07/14 23:38:13 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -2364,7 +2364,7 @@ CommentStmt:
 			IS comment_text
 				{
 					CommentStmt *n = makeNode(CommentStmt);
-					n->objtype = AGGREGATE;
+					n->objtype = COMMENT_ON_AGGREGATE;
 					n->objname = $4;
 					n->objargs = makeList1($6);
 					n->comment = $9;
@@ -2373,7 +2373,7 @@ CommentStmt:
 			| COMMENT ON FUNCTION func_name func_args IS comment_text
 				{
 					CommentStmt *n = makeNode(CommentStmt);
-					n->objtype = FUNCTION;
+					n->objtype = COMMENT_ON_FUNCTION;
 					n->objname = $4;
 					n->objargs = $5;
 					n->comment = $7;
@@ -2383,16 +2383,16 @@ CommentStmt:
 			IS comment_text
 				{
 					CommentStmt *n = makeNode(CommentStmt);
-					n->objtype = OPERATOR;
+					n->objtype = COMMENT_ON_OPERATOR;
 					n->objname = $4;
 					n->objargs = $6;
 					n->comment = $9;
 					$$ = (Node *) n;
 				}
-			| COMMENT ON TRIGGER name ON any_name IS comment_text
+			| COMMENT ON CONSTRAINT name ON any_name IS comment_text
 				{
 					CommentStmt *n = makeNode(CommentStmt);
-					n->objtype = TRIGGER;
+					n->objtype = COMMENT_ON_CONSTRAINT;
 					n->objname = lappend($6, makeString($4));
 					n->objargs = NIL;
 					n->comment = $8;
@@ -2401,7 +2401,7 @@ CommentStmt:
 			| COMMENT ON RULE name ON any_name IS comment_text
 				{
 					CommentStmt *n = makeNode(CommentStmt);
-					n->objtype = RULE;
+					n->objtype = COMMENT_ON_RULE;
 					n->objname = lappend($6, makeString($4));
 					n->objargs = NIL;
 					n->comment = $8;
@@ -2411,29 +2411,38 @@ CommentStmt:
 				{
 					/* Obsolete syntax supported for awhile for compatibility */
 					CommentStmt *n = makeNode(CommentStmt);
-					n->objtype = RULE;
+					n->objtype = COMMENT_ON_RULE;
 					n->objname = makeList1(makeString($4));
 					n->objargs = NIL;
 					n->comment = $6;
 					$$ = (Node *) n;
 				}
+			| COMMENT ON TRIGGER name ON any_name IS comment_text
+				{
+					CommentStmt *n = makeNode(CommentStmt);
+					n->objtype = COMMENT_ON_TRIGGER;
+					n->objname = lappend($6, makeString($4));
+					n->objargs = NIL;
+					n->comment = $8;
+					$$ = (Node *) n;
+				}
 		;
 
 comment_type:
-			COLUMN									{ $$ = COLUMN; }
-			| DATABASE								{ $$ = DATABASE; }
-			| SCHEMA								{ $$ = SCHEMA; }
-			| INDEX									{ $$ = INDEX; }
-			| SEQUENCE								{ $$ = SEQUENCE; }
-			| TABLE									{ $$ = TABLE; }
-			| DOMAIN_P								{ $$ = TYPE_P; }
-			| TYPE_P								{ $$ = TYPE_P; }
-			| VIEW									{ $$ = VIEW; }
+			COLUMN								{ $$ = COMMENT_ON_COLUMN; }
+			| DATABASE							{ $$ = COMMENT_ON_DATABASE; }
+			| SCHEMA							{ $$ = COMMENT_ON_SCHEMA; }
+			| INDEX								{ $$ = COMMENT_ON_INDEX; }
+			| SEQUENCE							{ $$ = COMMENT_ON_SEQUENCE; }
+			| TABLE								{ $$ = COMMENT_ON_TABLE; }
+			| DOMAIN_P							{ $$ = COMMENT_ON_TYPE; }
+			| TYPE_P							{ $$ = COMMENT_ON_TYPE; }
+			| VIEW								{ $$ = COMMENT_ON_VIEW; }
 		;
 
 comment_text:
-			Sconst									{ $$ = $1; }
-			| NULL_P								{ $$ = NULL; }
+			Sconst								{ $$ = $1; }
+			| NULL_P							{ $$ = NULL; }
 		;
 
 /*****************************************************************************

src/include/nodes/parsenodes.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: parsenodes.h,v 1.185 2002/07/12 18:43:19 tgl Exp $
+ * $Id: parsenodes.h,v 1.186 2002/07/14 23:38:13 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1165,10 +1165,25 @@ typedef struct TruncateStmt
  *				Comment On Statement
  * ----------------------
  */
+#define COMMENT_ON_AGGREGATE	100
+#define COMMENT_ON_COLUMN		101
+#define COMMENT_ON_CONSTRAINT	102
+#define COMMENT_ON_DATABASE		103
+#define COMMENT_ON_FUNCTION		104
+#define COMMENT_ON_INDEX		105
+#define COMMENT_ON_OPERATOR		106
+#define COMMENT_ON_RULE			107
+#define COMMENT_ON_SCHEMA		108
+#define COMMENT_ON_SEQUENCE		109
+#define COMMENT_ON_TABLE		110
+#define COMMENT_ON_TRIGGER		111
+#define COMMENT_ON_TYPE			112
+#define COMMENT_ON_VIEW			113
+
 typedef struct CommentStmt
 {
 	NodeTag		type;
-	int			objtype;		/* Object's type */
+	int			objtype;		/* Object's type, see codes above */
 	List	   *objname;		/* Qualified name of the object */
 	List	   *objargs;		/* Arguments if needed (eg, for functions) */
 	char	   *comment;		/* Comment to insert, or NULL to remove */