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;