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branches/innodb+: ibuf_insert_low(): Remove a race condition related to

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buf_pool_watch_occurred() and add explaining comments.
This commit is contained in:
marko 2008-12-04 08:09:40 +00:00
parent 13ee04a24c
commit 8b4a0686a8
1 changed files with 23 additions and 13 deletions
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36
ibuf/ibuf0ibuf.c
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@ -3249,14 +3249,6 @@ ibuf_insert_low(
btr_pcur_open(ibuf->index, ibuf_entry, PAGE_CUR_LE, mode, &pcur, &mtr);
/* Don't buffer deletes if the page has been read in to the buffer
pool. */
if (op == IBUF_OP_DELETE && buf_pool_watch_occurred(space, page_no)) {
err = DB_STRONG_FAIL;
goto function_exit;
}
/* Find out the volume of already buffered inserts for the same index
page */
min_n_recs = 0;
@ -3265,12 +3257,30 @@ ibuf_insert_low(
? &min_n_recs
: NULL, &mtr);
if (op == IBUF_OP_DELETE && min_n_recs < 2) {
/* The page could become empty after the record is
deleted. Refuse to buffer the operation. */
err = DB_STRONG_FAIL;
if (op == IBUF_OP_DELETE) {
if (min_n_recs < 2
|| buf_pool_watch_occurred(space, page_no)) {
/* The page could become empty after the
record is deleted, or the page has been read
in to the buffer pool. Refuse to buffer the
operation. */
err = DB_STRONG_FAIL;
goto function_exit;
goto function_exit;
}
/* The buffer pool watch is needed for IBUF_OP_DELETE
because of latching order considerations. We can
check buf_pool_watch_occurred() only after latching
the insert buffer B-tree pages that contain buffered
changes for the page. We never buffer IBUF_OP_DELETE,
unless some IBUF_OP_INSERT or IBUF_OP_DELETE_MARK have
been previously buffered for the page. Because there
are buffered operations for the page, the insert
buffer B-tree page latches held by mtr will guarantee
that no changes for the user page will be merged
before mtr_commit(&mtr). We must not mtr_commit(&mtr)
until after the IBUF_OP_DELETE has been buffered. */
}
#ifdef UNIV_IBUF_COUNT_DEBUG