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Commit fd7a1118 authored by Marko Mäkelä's avatar Marko Mäkelä
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Merge Bug #54358 comment corrections from mysql-5.1-innodb: 

------------------------------------------------------------
revno: 3533
revision-id: marko.makela@oracle.com-20100630093149-wmc37t128gic933v
parent: marko.makela@oracle.com-20100629131219-pjbkpk5rsqztmw27
committer: Marko Mäkelä <marko.makela@oracle.com>
branch nick: 5.1-innodb
timestamp: Wed 2010-06-30 12:31:49 +0300
message:
  Correct some comments that were added in the fix of Bug #54358
  (READ UNCOMMITTED access failure of off-page DYNAMIC or COMPRESSED columns).

  Records that lack incompletely written externally stored columns may
  be accessed by READ UNCOMMITTED transaction even without involving a
  crash during an INSERT or UPDATE operation. I verified this as follows.

  (1) added a delay after the mini-transaction for writing the clustered
  index 'stub' record was committed (patch attached)
  (2) started mysqld in gdb, setting breakpoints to the where the
  assertions about READ UNCOMMITTED were added in the bug fix
  (3) invoked ibtest3 --create-options=key_block_size=2
  to create BLOBs in a COMPRESSED table
  (4) invoked the following:
  yes 'set transaction isolation level read uncommitted;
  checksum table blobt3;select sleep(1);'|mysql -uroot test
  (5) noted that one of the breakpoints was triggered
  (return(NULL) in btr_rec_copy_externally_stored_field())

  === modified file 'storage/innodb_plugin/row/row0ins.c'
  --- storage/innodb_plugin/row/row0ins.c	2010-06-30 08:17:25 +0000
  +++ storage/innodb_plugin/row/row0ins.c	2010-06-30 08:17:25 +0000
  @@ -2120,6 +2120,7 @@ function_exit:
   		rec_t*	rec;
   		ulint*	offsets;
   		mtr_start(&mtr);
  +		os_thread_sleep(5000000);
   
   		btr_cur_search_to_nth_level(index, 0, entry, PAGE_CUR_LE,
   					    BTR_MODIFY_TREE, &cursor, 0,
  
  === modified file 'storage/innodb_plugin/row/row0upd.c'
  --- storage/innodb_plugin/row/row0upd.c	2010-06-30 08:11:55 +0000
  +++ storage/innodb_plugin/row/row0upd.c	2010-06-30 08:11:55 +0000
  @@ -1763,6 +1763,7 @@ row_upd_clust_rec(
   		rec_offs_init(offsets_);
   
   		mtr_start(mtr);
  +		os_thread_sleep(5000000);
   
   		ut_a(btr_pcur_restore_position(BTR_MODIFY_TREE, pcur, mtr));
   		rec = btr_cur_get_rec(btr_cur);
parent aab20dd8
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Showing with 19 additions and 48 deletions
storage/innobase/btr/btr0cur.c
View file @ fd7a1118
......@@ -4969,20 +4969,10 @@ btr_rec_copy_externally_stored_field(
if (UNIV_UNLIKELY
(!memcmp(data + local_len - BTR_EXTERN_FIELD_REF_SIZE,
field_ref_zero, BTR_EXTERN_FIELD_REF_SIZE))) {
/* The externally stored field was not written
yet. This is only a valid condition when the server
crashed after the time a record stub was freshly
inserted but before all its columns were written. This
record should only be seen by
/* The externally stored field was not written yet.
This record should only be seen by
recv_recovery_rollback_active() or any
TRX_ISO_READ_UNCOMMITTED transactions. */
/* TODO: assert that there is an owner_trx with
owner_trx->id == DB_TRX_ID and owner_trx->is_recovered */
/* TODO: assert that for the current transaction trx,
either (trx == owner_trx && trx_is_recv(trx)) or
trx->isolation_level == TRX_ISO_READ_UNCOMMITTED. */
return(NULL);
}
......
storage/innobase/row/row0sel.c
View file @ fd7a1118
......@@ -425,11 +425,7 @@ row_sel_fetch_columns(
/* data == NULL means that the
externally stored field was not
written yet. This is only a valid
condition when the server crashed
after the time a record stub was
freshly inserted but before all its
columns were written. This record
written yet. This record
should only be seen by
recv_recovery_rollback_active() or any
TRX_ISO_READ_UNCOMMITTED
......@@ -2736,12 +2732,7 @@ row_sel_store_mysql_rec(
if (UNIV_UNLIKELY(!data)) {
/* The externally stored field
was not written yet. This is
only a valid condition when
the server crashed after the
time a record stub was freshly
inserted but before all its
columns were written. This
was not written yet. This
record should only be seen by
recv_recovery_rollback_active()
or any TRX_ISO_READ_UNCOMMITTED
......@@ -3615,8 +3606,7 @@ row_search_for_mysql(
if (!row_sel_store_mysql_rec(buf, prebuilt,
rec, offsets)) {
/* Only fresh inserts at
server crash time may contain
/* Only fresh inserts may contain
incomplete externally stored
columns. Pretend that such
records do not exist. Such
......@@ -3628,10 +3618,6 @@ row_search_for_mysql(
at a lower level, not here. */
ut_a(trx->isolation_level
== TRX_ISO_READ_UNCOMMITTED);
/* TODO: assert that there is
an owner_trx with
owner_trx->id == DB_TRX_ID and
owner_trx->is_recovered */
err = DB_TOO_BIG_RECORD;
......@@ -4414,16 +4400,14 @@ row_search_for_mysql(
if (!row_sel_push_cache_row_for_mysql(prebuilt, result_rec,
offsets)) {
/* Only fresh inserts at server crash time may contain
incomplete externally stored columns. Pretend that
such records do not exist. Such records may only be
accessed at the READ UNCOMMITTED isolation level or
when rolling back a recovered transaction. Rollback
happens at a lower level, not here. */
/* Only fresh inserts may contain incomplete
externally stored columns. Pretend that such
records do not exist. Such records may only be
accessed at the READ UNCOMMITTED isolation
level or when rolling back a recovered
transaction. Rollback happens at a lower
level, not here. */
ut_a(trx->isolation_level == TRX_ISO_READ_UNCOMMITTED);
/* TODO: assert that there is an owner_trx
with owner_trx->id == DB_TRX_ID and
owner_trx->is_recovered */
} else if (prebuilt->n_fetch_cached
== MYSQL_FETCH_CACHE_SIZE) {
......@@ -4441,19 +4425,16 @@ row_search_for_mysql(
} else {
if (!row_sel_store_mysql_rec(buf, prebuilt,
result_rec, offsets)) {
/* Only fresh inserts at server crash
time may contain incomplete externally
stored columns. Pretend that such
records do not exist. Such records may
only be accessed at the READ UNCOMMITTED
/* Only fresh inserts may contain
incomplete externally stored
columns. Pretend that such records do
not exist. Such records may only be
accessed at the READ UNCOMMITTED
isolation level or when rolling back a
recovered transaction. Rollback happens
at a lower level, not here. */
recovered transaction. Rollback
happens at a lower level, not here. */
ut_a(trx->isolation_level
== TRX_ISO_READ_UNCOMMITTED);
/* TODO: assert that there is an owner_trx
with owner_trx->id == DB_TRX_ID and
owner_trx->is_recovered */
goto next_rec;
}
}
......
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