Adjust creation/destruction of TupleDesc data structure to reduce the

number of palloc calls.  This has a salutory impact on plpgsql operations
with record variables (which create and destroy tupdescs constantly)
and probably helps a bit in some other cases too.

1 files changed, 12 insertions, 8 deletions

diff --git a/src/include/access/tupdesc.h b/src/include/access/tupdesc.h
index 8ffb2e70c85..f9b89ed253c 100644
--- a/src/include/access/tupdesc.h
+++ b/src/include/access/tupdesc.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/tupdesc.h,v 1.46 2004/12/31 22:03:21 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/access/tupdesc.h,v 1.47 2005/03/07 04:42:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -42,13 +42,17 @@ typedef struct tupleConstr
 } TupleConstr;
 
 /*
- * This structure contains all information (i.e. from Classes
- * pg_attribute, pg_attrdef, pg_constraint) for the structure of a tuple.
+ * This struct is passed around within the backend to describe the structure
+ * of tuples.  For tuples coming from on-disk relations, the information is
+ * collected from the pg_attribute, pg_attrdef, and pg_constraint catalogs.
+ * Transient row types (such as the result of a join query) have anonymous
+ * TupleDesc structs that generally omit any constraint info; therefore the
+ * structure is designed to let the constraints be omitted efficiently.
  *
  * Note that only user attributes, not system attributes, are mentioned in
  * TupleDesc; with the exception that tdhasoid indicates if OID is present.
  *
- * If the tuple is known to correspond to a named rowtype (such as a table's
+ * If the tupdesc is known to correspond to a named rowtype (such as a table's
  * rowtype) then tdtypeid identifies that type and tdtypmod is -1.	Otherwise
  * tdtypeid is RECORDOID, and tdtypmod can be either -1 for a fully anonymous
  * row type, or a value >= 0 to allow the rowtype to be looked up in the
@@ -56,13 +60,13 @@ typedef struct tupleConstr
  */
 typedef struct tupleDesc
 {
-	int			natts;			/* Number of attributes in the tuple */
+	int			natts;			/* number of attributes in the tuple */
 	Form_pg_attribute *attrs;
-	/* attrs[N] is a pointer to the description of Attribute Number N+1.  */
-	TupleConstr *constr;
+	/* attrs[N] is a pointer to the description of Attribute Number N+1 */
+	TupleConstr *constr;		/* constraints, or NULL if none */
 	Oid			tdtypeid;		/* composite type ID for tuple type */
 	int32		tdtypmod;		/* typmod for tuple type */
-	bool		tdhasoid;		/* Tuple has oid attribute in its header */
+	bool		tdhasoid;		/* tuple has oid attribute in its header */
 }	*TupleDesc;