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Fix for bug #35732: read-only blocks SELECT statements in InnoDB

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Problem: SELECTs prohibited for a transactional SE in autocommit mode
if read_only is set.

Fix: allow them.


mysql-test/r/read_only_innodb.result:
  Fix for bug #35732: read-only blocks SELECT statements in InnoDB
    - test result.
mysql-test/t/read_only_innodb.test:
  Fix for bug #35732: read-only blocks SELECT statements in InnoDB
    - test case.
sql/handler.cc:
  Fix for bug #35732: read-only blocks SELECT statements in InnoDB
    - in autocommit mode thd->transaction.all list is empty thus 
      is_real_trans set to TRUE for any SELECTs, so using it in the
      "read_only" check is insufficient.
      ha_check_and_coalesce_trx_read_only() changed to return number
      of engines with read-write changes. This value is used in the
      "read-only" check and checks for GLOBAL READ LOCK.
sql/lock.cc:
  Fix for bug #35732: read-only blocks SELECT statements in InnoDB
    - added assert(protect_against_global_read_lock) before decreasing,
      in order to catch (uint) 0 - 1 situation due to wrong 
      wait_if_global_read_lock()/start_waiting_global_read_lock() call
      sequence.
This commit is contained in:
unknown
2008-04-08 10:20:58 +05:00
parent ccd31e9dd4
commit 9fd89afca0
4 changed files with 110 additions and 29 deletions
Download Patch File Download Diff File Expand all files Collapse all files

66
sql/handler.cc
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@@ -952,16 +952,21 @@ int ha_prepare(THD *thd)
A helper function to evaluate if two-phase commit is mandatory.
As a side effect, propagates the read-only/read-write flags
of the statement transaction to its enclosing normal transaction.
If we have at least two engines with read-write changes we must
run a two-phase commit. Otherwise we can run several independent
commits as the only transactional engine has read-write changes
and others are read-only.
@retval TRUE we must run a two-phase commit. Returned
if we have at least two engines with read-write changes.
@retval FALSE Don't need two-phase commit. Even if we have two
transactional engines, we can run two independent
commits if changes in one of the engines are read-only.
@retval 0 All engines are read-only.
@retval 1 We have the only engine with read-write changes.
@retval >1 More than one engine have read-write changes.
Note: return value might NOT be the exact number of
engines with read-write changes.
*/
static
bool
uint
ha_check_and_coalesce_trx_read_only(THD *thd, Ha_trx_info *ha_list,
bool all)
{
@@ -998,7 +1003,7 @@ ha_check_and_coalesce_trx_read_only(THD *thd, Ha_trx_info *ha_list,
break;
}
}
return rw_ha_count > 1;
return rw_ha_count;
}
@@ -1061,25 +1066,8 @@ int ha_commit_trans(THD *thd, bool all)
#ifdef USING_TRANSACTIONS
if (ha_info)
{
bool must_2pc;
if (is_real_trans && wait_if_global_read_lock(thd, 0, 0))
{
ha_rollback_trans(thd, all);
DBUG_RETURN(1);
}
if ( is_real_trans
&& opt_readonly
&& ! (thd->security_ctx->master_access & SUPER_ACL)
&& ! thd->slave_thread
)
{
my_error(ER_OPTION_PREVENTS_STATEMENT, MYF(0), "--read-only");
ha_rollback_trans(thd, all);
error= 1;
goto end;
}
uint rw_ha_count;
bool rw_trans;
DBUG_EXECUTE_IF("crash_commit_before", abort(););
@@ -1087,9 +1075,29 @@ int ha_commit_trans(THD *thd, bool all)
if (is_real_trans) /* not a statement commit */
thd->stmt_map.close_transient_cursors();
must_2pc= ha_check_and_coalesce_trx_read_only(thd, ha_info, all);
rw_ha_count= ha_check_and_coalesce_trx_read_only(thd, ha_info, all);
/* rw_trans is TRUE when we in a transaction changing data */
rw_trans= is_real_trans && (rw_ha_count > 0);
if (!trans->no_2pc && must_2pc)
if (rw_trans &&
wait_if_global_read_lock(thd, 0, 0))
{
ha_rollback_trans(thd, all);
DBUG_RETURN(1);
}
if (rw_trans &&
opt_readonly &&
!(thd->security_ctx->master_access & SUPER_ACL) &&
!thd->slave_thread)
{
my_error(ER_OPTION_PREVENTS_STATEMENT, MYF(0), "--read-only");
ha_rollback_trans(thd, all);
error= 1;
goto end;
}
if (!trans->no_2pc && (rw_ha_count > 1))
{
for (; ha_info && !error; ha_info= ha_info->next())
{
@@ -1129,7 +1137,7 @@ int ha_commit_trans(THD *thd, bool all)
tc_log->unlog(cookie, xid);
DBUG_EXECUTE_IF("crash_commit_after", abort(););
end:
if (is_real_trans)
if (rw_trans)
start_waiting_global_read_lock(thd);
}
#endif /* USING_TRANSACTIONS */