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Improve comment: add note that grotty special case in mdread() is

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required by hash index implementation.
This commit is contained in:
Tom Lane
2002-11-12 15:26:30 +00:00
parent 90a06dba16
commit 6929a1e6ad
1 changed files with 7 additions and 3 deletions
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10
src/backend/storage/smgr/md.c
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@@ -8,7 +8,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/smgr/md.c,v 1.92 2002/08/06 02:36:34 tgl Exp $ * $Header: /cvsroot/pgsql/src/backend/storage/smgr/md.c,v 1.93 2002/11/12 15:26:30 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@@ -434,8 +434,12 @@ mdread(Relation reln, BlockNumber blocknum, char *buffer)
if ((nbytes = FileRead(v->mdfd_vfd, buffer, BLCKSZ)) != BLCKSZ) if ((nbytes = FileRead(v->mdfd_vfd, buffer, BLCKSZ)) != BLCKSZ)
{ {
/* /*
* If we are at EOF, return zeroes without complaining. (XXX Is * If we are at or past EOF, return zeroes without complaining.
* this still necessary/a good idea??) * Also substitute zeroes if we found a partial block at EOF.
*
* XXX this is really ugly, bad design. However the current
* implementation of hash indexes requires it, because hash index
* pages are initialized out-of-order.
*/ */
if (nbytes == 0 || if (nbytes == 0 ||
(nbytes > 0 && mdnblocks(reln) == blocknum)) (nbytes > 0 && mdnblocks(reln) == blocknum))