Add comments for attdisbursion field --- NO code change.

diff --git a/src/include/catalog/pg_attribute.h b/src/include/catalog/pg_attribute.h
index 466a0a2215b9a6d353ae1ae93643235bee764370..35f76c3a61f7e869f6a47857c2e43d37676a6317 100644 (file)
--- 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;