Implement SQL-standard WITH clauses, including WITH RECURSIVE.

There are some unimplemented aspects: recursive queries must use UNION ALL
(should allow UNION too), and we don't have SEARCH or CYCLE clauses.
These might or might not get done for 8.4, but even without them it's a
pretty useful feature.

There are also a couple of small loose ends and definitional quibbles,
which I'll send a memo about to pgsql-hackers shortly.  But let's land
the patch now so we can get on with other development.

Yoshiyuki Asaba, with lots of help from Tatsuo Ishii and Tom Lane

1 files changed, 102 insertions, 6 deletions

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 71fea45ddd0..fd21152b495 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.284 2008/09/06 20:18:08 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.285 2008/10/04 21:56:54 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -145,6 +145,7 @@ static void make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 static void get_query_def(Query *query, StringInfo buf, List *parentnamespace,
 			  TupleDesc resultDesc, int prettyFlags, int startIndent);
 static void get_values_def(List *values_lists, deparse_context *context);
+static void get_with_clause(Query *query, deparse_context *context);
 static void get_select_query_def(Query *query, deparse_context *context,
 					 TupleDesc resultDesc);
 static void get_insert_query_def(Query *query, deparse_context *context);
@@ -2205,6 +2206,73 @@ get_values_def(List *values_lists, deparse_context *context)
 }
 
 /* ----------
+ * get_with_clause			- Parse back a WITH clause
+ * ----------
+ */
+static void
+get_with_clause(Query *query, deparse_context *context)
+{
+	StringInfo	buf = context->buf;
+	const char	*sep;
+	ListCell	*l;
+
+	if (query->cteList == NIL)
+		return;
+
+	if (PRETTY_INDENT(context))
+	{
+		context->indentLevel += PRETTYINDENT_STD;
+		appendStringInfoChar(buf, ' ');
+	}
+
+	if (query->hasRecursive)
+		sep = "WITH RECURSIVE ";
+	else
+		sep = "WITH ";
+	foreach(l, query->cteList)
+	{
+		CommonTableExpr *cte = (CommonTableExpr *) lfirst(l);
+
+		appendStringInfoString(buf, sep);
+		appendStringInfoString(buf, quote_identifier(cte->ctename));
+		if (cte->aliascolnames)
+		{
+			bool		first = true;
+			ListCell   *col;
+
+			appendStringInfoChar(buf, '(');
+			foreach(col, cte->aliascolnames)
+			{
+				if (first)
+					first = false;
+				else
+					appendStringInfoString(buf, ", ");
+				appendStringInfoString(buf,
+									   quote_identifier(strVal(lfirst(col))));
+			}
+			appendStringInfoChar(buf, ')');
+		}
+		appendStringInfoString(buf, " AS (");
+		if (PRETTY_INDENT(context))
+			appendContextKeyword(context, "", 0, 0, 0);
+		get_query_def((Query *) cte->ctequery, buf, context->namespaces, NULL,
+					  context->prettyFlags, context->indentLevel);
+		if (PRETTY_INDENT(context))
+			appendContextKeyword(context, "", 0, 0, 0);
+		appendStringInfoChar(buf, ')');
+		sep = ", ";
+	}
+
+	if (PRETTY_INDENT(context))
+	{
+		context->indentLevel -= PRETTYINDENT_STD;
+		appendContextKeyword(context, "", 0, 0, 0);
+	}
+	else
+		appendStringInfoChar(buf, ' ');
+}
+
+/* ----------
  * get_select_query_def			- Parse back a SELECT parsetree
  * ----------
  */
@@ -2214,13 +2282,16 @@ get_select_query_def(Query *query, deparse_context *context,
 {
 	StringInfo	buf = context->buf;
 	bool		force_colno;
-	char	   *sep;
+	const char *sep;
 	ListCell   *l;
 
+	/* Insert the WITH clause if given */
+	get_with_clause(query, context);
+
 	/*
 	 * If the Query node has a setOperations tree, then it's the top level of
-	 * a UNION/INTERSECT/EXCEPT query; only the ORDER BY and LIMIT fields are
-	 * interesting in the top query itself.
+	 * a UNION/INTERSECT/EXCEPT query; only the WITH, ORDER BY and LIMIT
+	 * fields are interesting in the top query itself.
 	 */
 	if (query->setOperations)
 	{
@@ -2507,8 +2578,9 @@ get_setop_query(Node *setOp, Query *query, deparse_context *context,
 
 		Assert(subquery != NULL);
 		Assert(subquery->setOperations == NULL);
-		/* Need parens if ORDER BY, FOR UPDATE, or LIMIT; see gram.y */
-		need_paren = (subquery->sortClause ||
+		/* Need parens if WITH, ORDER BY, FOR UPDATE, or LIMIT; see gram.y */
+		need_paren = (subquery->cteList ||
+					  subquery->sortClause ||
 					  subquery->rowMarks ||
 					  subquery->limitOffset ||
 					  subquery->limitCount);
@@ -2523,6 +2595,12 @@ get_setop_query(Node *setOp, Query *query, deparse_context *context,
 	{
 		SetOperationStmt *op = (SetOperationStmt *) setOp;
 
+		if (PRETTY_INDENT(context))
+		{
+			context->indentLevel += PRETTYINDENT_STD;
+			appendStringInfoSpaces(buf, PRETTYINDENT_STD);
+		}
+
 		/*
 		 * We force parens whenever nesting two SetOperationStmts. There are
 		 * some cases in which parens are needed around a leaf query too, but
@@ -2570,6 +2648,9 @@ get_setop_query(Node *setOp, Query *query, deparse_context *context,
 		get_setop_query(op->rarg, query, context, resultDesc);
 		if (need_paren)
 			appendStringInfoChar(buf, ')');
+
+		if (PRETTY_INDENT(context))
+			context->indentLevel -= PRETTYINDENT_STD;
 	}
 	else
 	{
@@ -2730,11 +2811,15 @@ get_insert_query_def(Query *query, deparse_context *context)
 	}
 	else if (values_rte)
 	{
+		/* A WITH clause is possible here */
+		get_with_clause(query, context);
 		/* Add the multi-VALUES expression lists */
 		get_values_def(values_rte->values_lists, context);
 	}
 	else
 	{
+		/* A WITH clause is possible here */
+		get_with_clause(query, context);
 		/* Add the single-VALUES expression list */
 		appendContextKeyword(context, "VALUES (",
 							 -PRETTYINDENT_STD, PRETTYINDENT_STD, 2);
@@ -3360,6 +3445,13 @@ get_name_for_var_field(Var *var, int fieldno,
 			 * its result columns as RECORD, which is not allowed.
 			 */
 			break;
+		case RTE_CTE:
+			/*
+			 * XXX not implemented yet, we need more infrastructure in
+			 * deparse_namespace and explain.c.
+			 */
+			elog(ERROR, "deparsing field references to whole-row vars from WITH queries not implemented yet");
+			break;
 	}
 
 	/*
@@ -5029,6 +5121,7 @@ get_sublink_expr(SubLink *sublink, deparse_context *context)
 			need_paren = false;
 			break;
 
+		case CTE_SUBLINK:		/* shouldn't occur in a SubLink */
 		default:
 			elog(ERROR, "unrecognized sublink type: %d",
 				 (int) sublink->subLinkType);
@@ -5130,6 +5223,9 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 				/* Values list RTE */
 				get_values_def(rte->values_lists, context);
 				break;
+			case RTE_CTE:
+				appendStringInfoString(buf, quote_identifier(rte->ctename));
+				break;
 			default:
 				elog(ERROR, "unrecognized RTE kind: %d", (int) rte->rtekind);
 				break;