From cf835f97fc67a6b189c80c62239135238ede5b13 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sat, 31 Jul 1999 19:07:25 +0000
Subject: [PATCH] Add comments for attdisbursion field --- NO code change.
---
src/include/catalog/pg_attribute.h | 33 +++++++++++++++---------------
1 file changed, 17 insertions(+), 16 deletions(-)
diff --git a/src/include/catalog/pg_attribute.h b/src/include/catalog/pg_attribute.h
index 466a0a2215b..35f76c3a61f 100644
--- a/src/include/catalog/pg_attribute.h
+++ b/src/include/catalog/pg_attribute.h
@@ -7,7 +7,7 @@
*
* Copyright (c) 1994, Regents of the University of California
*
- * $Id: pg_attribute.h,v 1.47 1999/05/25 16:13:42 momjian Exp $
+ * $Id: pg_attribute.h,v 1.48 1999/07/31 19:07:25 tgl Exp $
*
* NOTES
* the genbki.sh script reads this file and generates .bki
@@ -40,10 +40,9 @@
*/
CATALOG(pg_attribute) BOOTSTRAP
{
- Oid attrelid;
+ Oid attrelid; /* OID of relation containing this attribute */
NameData attname;
Oid atttypid;
-
/*
* atttypid is the OID of the instance in Catalog Class pg_type that
* defines the data type of this attribute (e.g. int4). Information
@@ -51,16 +50,21 @@ CATALOG(pg_attribute) BOOTSTRAP
* attalign attributes of this instance, so they had better match or
* Postgres will fail.
*/
+
float4 attdisbursion;
- int2 attlen;
+ /*
+ * attdisbursion is the disbursion statistic of the column, or zero if
+ * the statistic has not been calculated.
+ */
+ int2 attlen;
/*
* attlen is a copy of the typlen field from pg_type for this
* attribute. See atttypid above. See struct Form_pg_type for
* definition.
*/
- int2 attnum;
+ int2 attnum;
/*
* attnum is the "attribute number" for the attribute: A value that
* uniquely identifies this attribute within its class. For user
@@ -74,28 +78,27 @@ CATALOG(pg_attribute) BOOTSTRAP
*
* Note that (attnum - 1) is often used as the index to an array.
*/
- int4 attnelems;
- int4 attcacheoff;
+ int4 attnelems; /* number of dimensions, if an array type */
+ int4 attcacheoff;
/*
* fastgetattr() uses attcacheoff to cache byte offsets of attributes
- * in heap tuples. The data actually stored in pg_attribute (-1)
+ * in heap tuples. The value actually stored in pg_attribute (-1)
* indicates no cached value. But when we copy these tuples into a
* tuple descriptor, we may then update attcacheoff in the copies.
* This speeds up the attribute walking process.
*/
int4 atttypmod;
-
/*
- * atttypmod records type-specific modifications supplied at table
- * creation time, and passes it to input and output functions as the
- * third argument.
+ * atttypmod records type-specific data supplied at table creation time
+ * (for example, the max length of a varchar field). It is passed to
+ * type-specific input and output functions as the third argument.
+ * The value will generally be -1 for types that do not need typmod.
*/
bool attbyval;
-
/*
* attbyval is a copy of the typbyval field from pg_type for this
* attribute. See atttypid above. See struct Form_pg_type for
@@ -103,17 +106,15 @@ CATALOG(pg_attribute) BOOTSTRAP
*/
bool attisset;
char attalign;
-
/*
* attalign is a copy of the typalign field from pg_type for this
* attribute. See atttypid above. See struct Form_pg_type for
* definition.
*/
- bool attnotnull;
+ bool attnotnull;
/* This flag represents the "NOT NULL" constraint */
bool atthasdef;
-
/* Has DEFAULT value or not */
} FormData_pg_attribute;
--
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