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Add comments defining "typelem" column of pg_type.

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Bryan Henderson
1996-12-09 01:23:51 +00:00
parent b36e3042e7
commit 79729c0e5e
1 changed files with 11 additions and 7 deletions
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18
src/include/catalog/pg_type.h
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@@ -7,7 +7,7 @@
* *
* Copyright (c) 1994, Regents of the University of California * Copyright (c) 1994, Regents of the University of California
* *
* $Id: pg_type.h,v 1.4 1996/11/13 20:51:06 scrappy Exp $ * $Id: pg_type.h,v 1.5 1996/12/09 01:23:51 bryanh Exp $
* *
* NOTES * NOTES
* the genbki.sh script reads this file and generates .bki * the genbki.sh script reads this file and generates .bki
@@ -43,17 +43,17 @@ CATALOG(pg_type) BOOTSTRAP {
int2 typlen; int2 typlen;
/* typlen is the number of bytes we use to represent a value of /* typlen is the number of bytes we use to represent a value of
this type, e.g. 4 for an int4. But for a variable length this type, e.g. 4 for an int4. But for a variable length
attribute, typlen is -1. type, typlen is -1.
*/ */
int2 typprtlen; int2 typprtlen;
bool typbyval; bool typbyval;
/* typbyval determines whether internal Postgres routines pass a value /* typbyval determines whether internal Postgres routines pass a value
of this type by value or by reference. Postgres uses a 4 byte of this type by value or by reference. Postgres uses a 4 byte
area for passing class data, so if the value is not 1, 2, area for passing a field value info, so if the value is not 1, 2,
or 4 bytes long, Postgres does not have the option of passing by or 4 bytes long, Postgres does not have the option of passing by
value and ignores typbyval. value and ignores typbyval.
(I don't understand why this attribute exists. The above description (I don't understand why this column exists. The above description
may be an oversimplification. Also, there appear to be bugs in which may be an oversimplification. Also, there appear to be bugs in which
Postgres doesn't ignore typbyval when it should, but I'm Postgres doesn't ignore typbyval when it should, but I'm
afraid to change them until I see proof of damage. -BRYANH 96.08). afraid to change them until I see proof of damage. -BRYANH 96.08).
@@ -63,6 +63,10 @@ CATALOG(pg_type) BOOTSTRAP {
char typdelim; char typdelim;
Oid typrelid; Oid typrelid;
Oid typelem; Oid typelem;
/* typelem is NULL if this is not an array type. If this is an array
type, typelem is the OID of the type of the elements of the array
(it identifies another row in Table pg_type).
*/
regproc typinput; regproc typinput;
regproc typoutput; regproc typoutput;
regproc typreceive; regproc typreceive;
@@ -71,7 +75,7 @@ CATALOG(pg_type) BOOTSTRAP {
/* typalign is the alignment required when storing a value of this /* typalign is the alignment required when storing a value of this
type. It applies to storage on disk as well as most representations type. It applies to storage on disk as well as most representations
of the value inside Postgres. When multiple values are stored of the value inside Postgres. When multiple values are stored
consecutively, such as in the representation of a complete tuple consecutively, such as in the representation of a complete row
on disk, padding is inserted before a datum of this type so that it on disk, padding is inserted before a datum of this type so that it
begins on the specified boundary. The alignment reference is the begins on the specified boundary. The alignment reference is the
beginning of the first datum in the sequence. beginning of the first datum in the sequence.
@@ -88,7 +92,7 @@ CATALOG(pg_type) BOOTSTRAP {
} TypeTupleFormData; } TypeTupleFormData;
/* ---------------- /* ----------------
* Form_pg_type corresponds to a pointer to a tuple with * Form_pg_type corresponds to a pointer to a row with
* the format of pg_type relation. * the format of pg_type relation.
* ---------------- * ----------------
*/ */
@@ -153,7 +157,7 @@ DATA(insert OID = 22 ( int28 PGUID 16 50 f b t \054 0 21 int28in int28ou
* go away someday. until that happens, there is a case (in the * go away someday. until that happens, there is a case (in the
* catalog cache management code) where we need to step gingerly * catalog cache management code) where we need to step gingerly
* over piles of int28's on the sidewalk. in order to do so, we * over piles of int28's on the sidewalk. in order to do so, we
* need the OID of the int28 tuple from pg_type. * need the OID of the int28 row from pg_type.
*/ */
#define INT28OID 22 #define INT28OID 22