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Adjust btree index build procedure so that the btree metapage looks

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invalid (has the wrong magic number) until the build is entirely
complete.  This turns out to cost no additional writes in the normal
case, since we were rewriting the metapage at the end of the process
anyway.  In normal scenarios there's no real gain in security, because
a failed index build would roll back the transaction leaving an unused
index file, but for rebuilding shared system indexes this seems to add
some useful protection.
This commit is contained in:
Tom Lane
2003-09-29 23:40:26 +00:00
parent 6b4caf53e6
commit e33f205a94
6 changed files with 71 additions and 28 deletions
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18
src/backend/access/nbtree/nbtpage.c
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@@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtpage.c,v 1.71 2003/09/25 06:57:57 petere Exp $
* $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtpage.c,v 1.72 2003/09/29 23:40:26 tgl Exp $
*
* NOTES
* Postgres btree pages look like ordinary relation pages. The opaque
@@ -31,12 +31,16 @@
/*
* _bt_metapinit() -- Initialize the metadata page of a new btree.
*
* If markvalid is true, the index is immediately marked valid, else it
* will be invalid until _bt_metaproot() is called.
*
* Note: there's no real need for any locking here. Since the transaction
* creating the index hasn't committed yet, no one else can even see the index
* much less be trying to use it.
* much less be trying to use it. (In a REINDEX-in-place scenario, that's
* not true, but we assume the caller holds sufficient locks on the index.)
*/
void
_bt_metapinit(Relation rel)
_bt_metapinit(Relation rel, bool markvalid)
{
Buffer buf;
Page pg;
@@ -57,7 +61,7 @@ _bt_metapinit(Relation rel)
_bt_pageinit(pg, BufferGetPageSize(buf));
metad = BTPageGetMeta(pg);
metad->btm_magic = BTREE_MAGIC;
metad->btm_magic = markvalid ? BTREE_MAGIC : 0;
metad->btm_version = BTREE_VERSION;
metad->btm_root = P_NONE;
metad->btm_level = 0;
@@ -85,7 +89,9 @@ _bt_metapinit(Relation rel)
rdata[0].len = SizeOfBtreeNewmeta;
rdata[0].next = NULL;
recptr = XLogInsert(RM_BTREE_ID, XLOG_BTREE_NEWMETA, rdata);
recptr = XLogInsert(RM_BTREE_ID,
markvalid ? XLOG_BTREE_NEWMETA : XLOG_BTREE_INVALIDMETA,
rdata);
PageSetLSN(pg, recptr);
PageSetSUI(pg, ThisStartUpID);
@@ -611,6 +617,8 @@ _bt_metaproot(Relation rel, BlockNumber rootbknum, uint32 level)
START_CRIT_SECTION();
metad = BTPageGetMeta(metap);
Assert(metad->btm_magic == BTREE_MAGIC || metad->btm_magic == 0);
metad->btm_magic = BTREE_MAGIC; /* it's valid now for sure */
metad->btm_root = rootbknum;
metad->btm_level = level;
metad->btm_fastroot = rootbknum;