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MDEV-20117: Fix another scenario

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Thanks to Eugene Kosov for noting that the fix is incomplete.
It turns out that on instant DROP/reorder column (MDEV-15562),
we must always write the metadata record, even though the table
was empty. Alternatively, we should guarantee that all undo
log records for the table have been purged. (Attempting to do
that by updating table_id leads to other problems; see
commit 1b31d8852c00b4bab6e6fe179b97db45ccb8d535.)

It would be tempting to remove dict_index_t::clear_instant_alter()
altogether, but it turns that we need that when the instant ALTER TABLE
operation of a first-time DROP COLUMN is being rolled back.

innobase_instant_try(): Clarify a comment. Purge never calls
dict_index_t::clear_instant_alter(), but it may invoke
dict_index_t::clear_instant_add(). On first-time instant DROP/reorder,
always write a metadata record, even if the table is empty.
This commit is contained in:
Marko Mäkelä 2019-09-27 16:01:55 +03:00
parent 1f4ee3fa5a
commit ea2b19dee6
3 changed files with 42 additions and 3 deletions
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15
mysql-test/suite/innodb/r/instant_alter_bugs.result
View file

@ -1,3 +1,5 @@
SET @save_frequency= @@GLOBAL.innodb_purge_rseg_truncate_frequency;
SET GLOBAL innodb_purge_rseg_truncate_frequency=1;
#
# MDEV-17821 Assertion `!page_rec_is_supremum(rec)' failed
# in btr_pcur_store_position
@ -295,3 +297,16 @@ ALTER TABLE t DROP COLUMN c, ALGORITHM=INSTANT;
SELECT * FROM t;
a b
DROP TABLE t;
CREATE TABLE t1 (a INT PRIMARY KEY, b INT, c INT, d INT, e INT) ENGINE=InnoDB;
INSERT INTO t1 SET a=1;
INSERT INTO t1 SET a=2;
BEGIN;
UPDATE t1 SET b=1;
DELETE FROM t1;
COMMIT;
ALTER TABLE t1 DROP b, DROP c, DROP d, DROP e;
InnoDB 0 transactions not purged
SELECT * FROM t1;
a
DROP TABLE t1;
SET GLOBAL innodb_purge_rseg_truncate_frequency=@save_frequency;

21
mysql-test/suite/innodb/t/instant_alter_bugs.test
View file

@ -1,5 +1,8 @@
--source include/have_innodb.inc
SET @save_frequency= @@GLOBAL.innodb_purge_rseg_truncate_frequency;
SET GLOBAL innodb_purge_rseg_truncate_frequency=1;
--echo #
--echo # MDEV-17821 Assertion `!page_rec_is_supremum(rec)' failed
--echo # in btr_pcur_store_position
@ -313,3 +316,21 @@ ALTER TABLE t ADD COLUMN c INT, ALGORITHM=INSTANT;
ALTER TABLE t DROP COLUMN c, ALGORITHM=INSTANT;
SELECT * FROM t;
DROP TABLE t;
# The following is nondeterministically repeating the bug in a
# different scenario: the table is empty at the time the ALTER TABLE
# is invoked, apparently because purge already processed the records
# for the DELETE, but not the record for the UPDATE.
CREATE TABLE t1 (a INT PRIMARY KEY, b INT, c INT, d INT, e INT) ENGINE=InnoDB;
INSERT INTO t1 SET a=1;
INSERT INTO t1 SET a=2;
BEGIN;
UPDATE t1 SET b=1;
DELETE FROM t1;
COMMIT;
ALTER TABLE t1 DROP b, DROP c, DROP d, DROP e;
--source include/wait_all_purged.inc
SELECT * FROM t1;
DROP TABLE t1;
SET GLOBAL innodb_purge_rseg_truncate_frequency=@save_frequency;

9
storage/innobase/handler/handler0alter.cc
View file

@ -5630,7 +5630,7 @@ static bool innobase_instant_try(
dict_index_t* index = dict_table_get_first_index(user_table);
mtr_t mtr;
mtr.start();
/* Prevent purge from calling dict_index_t::clear_instant_alter(),
/* Prevent purge from calling dict_index_t::clear_instant_add(),
to protect index->n_core_fields, index->table->instant and others
from changing during ctx->instant_column(). */
instant_metadata_lock(*index, mtr);
@ -5821,6 +5821,7 @@ add_all_virtual:
if (rec_is_metadata(rec, *index)) {
ut_ad(page_rec_is_user_rec(rec));
if (!rec_is_alter_metadata(rec, *index)
&& !index->table->instant
&& !page_has_next(block->frame)
&& page_rec_is_last(rec, block->frame)) {
goto empty_table;
@ -5902,7 +5903,7 @@ add_all_virtual:
}
btr_pcur_close(&pcur);
goto func_exit;
} else if (page_rec_is_supremum(rec)) {
} else if (page_rec_is_supremum(rec) && !index->table->instant) {
empty_table:
/* The table is empty. */
ut_ad(fil_page_index_page_check(block->frame));
@ -5910,7 +5911,9 @@ empty_table:
ut_ad(block->page.id.page_no() == index->page);
/* MDEV-17383: free metadata BLOBs! */
btr_page_empty(block, NULL, index, 0, &mtr);
index->clear_instant_alter();
if (index->is_instant()) {
index->clear_instant_add();
}
goto func_exit;
} else if (!user_table->is_instant()) {
ut_ad(!user_table->not_redundant());