This patch fills a serious flaw in the implementation of common table
expressions. Before this patch an attempt to prepare a statement from
a query with a parameter marker in a CTE that was used more than once
in the query ended up with a bogus error message. Similarly if a statement
in a stored procedure contained a CTE whose specification used a
local variables and this CTE was referred to more than once in the
statement then the server failed to execute the stored procedure returning
a bogus error message on a non-existing field.
The problems appeared due to incorrect handling of parameter markers /
local variables in CTEs that were referred more than once.
This patch fixes the problems by differentiating between the original
occurrences of a parameter marker / local variable used in the
specification of a CTE and the corresponding occurrences used
in copies of this specification. These copies are substituted
instead of non-first references to the CTE.
The idea of the fix and even some code were taken from the MySQL
implementation of the common table expressions.
materialized derived table/view that uses aliases is done
The problem appears when a column alias inside the materialized derived
table/view t1 definition coincides with the column name used in the
GROUP BY clause of t1. If the condition that can be pushed into t1
uses that ambiguous column name this column is determined as a column that
is used in the GROUP BY clause instead of the alias used in the projection
list of t1. That causes wrong result.
To prevent it resolve_ref_in_select_and_group() was changed.
The current code does not support recursive CTEs whose specifications
contain a mix of ALL UNION and DISTINCT UNION operations.
This patch catches such specifications and reports errors for them.
In this issue we hit the assert because we are adding addition fields to the field JOIN::all_fields list. This
is done because HEAP tables can't index BIT fields so we need to use an additional hidden field for grouping because later it will be
converted to a LONG field. Original field will remain of the BIT type and will be returned. This happens when we convert DISTINCT to
GROUP BY.
The solution is to take into account the number of such hidden fields that would be added to the field
JOIN::all_fields list while calculating the size of the ref_pointer_array.
Counter for select numbering made stored with the statement (before was global)
So now it does have always accurate value which does not depend on
interruption of statement prepare by errors like lack of table in
a view definition.
for a query that uses CTE
The first reference to a CTE in the processed query uses the unit
built by the parser for the CTE specification. This unit is
considered as the specification of the derived table created for
the first reference of the CTE. This requires some transformation of
the original query tree: the unit of the specification must be moved
to a new position as a slave of the select where the first reference
to the CTE occurs. The transformation is performed by the function
st_select_lex_node::move_as_slave(). There was an obvious bug in this
function. As a result of this bug in many cases the moved unit turned
out to be lost in the query tree. This could cause different problems.
In particular the prepared statements for queries that used CTEs could
miss cleanup for some selects that was performed at the end of the
preparation/execution of the PSs. If such cleanup is not done for a PS
the next execution of the PS causes an assertion abort or a crash.
Issue:
------
VALUES doesn't have a type() function and is considered a
Item_field.
Solution for 5.7:
-----------------
Add a new type() function for Item_values_insert.
On 8.0 and trunk it was fixed by Mithun's Bug#19601973.
Solution for 5.6:
-----------------
Additionally Bug#17458914 is backported.
This will address the problem of using VALUES() in
INSERT ... ON DUPLICATE KEY UPDATE. Create a field object
only if it is in the UPDATE clause, else return a NULL
item.
This will also address the problems mentioned in
Bug#14789787 and Bug#16756402.
Solution for 5.5:
-----------------
As mentioned above Bug#17458914 is backported.
Additionally Bug#14786324 is also backported.
When VALUES() is detected outside its meaningful place,
it should be treated as NULL and is thus replaced with a
Field_null object, with the same name as the original
field.
Fields with type NULL are generally not handled well inside
the server (e.g Innodb will not accept them and it is
impossible to create them in regular tables). So create a
new const NULL item instead.
As reported in MDEV-11969 "there's no way to ditch knowledge" about some
domain that is no longer updated on a server. Besides being of annoyance to
clutter output in DBA console stale domains can prevent the slave
to connect the master as MDEV-12012 witnesses.
What domain is obsolete must be evaluated by the user (DBA) according
to whether the domain info is still relevant and will the domain ever
receive any update.
This patch introduces a method to discard obsolete gtid domains from
the server binlog state. The removal requires no event group from such
domain present in existing binlog files though. If there are any the
containing logs must be first PURGEd in order for
FLUSH BINARY LOGS DELETE_DOMAIN_ID=(list-of-domains)
succeed. Otherwise the command returns an error.
The list of obsolete domains can be computed through
intersecting two sets - the earliest (first) binlog's Gtid_list
and the current value of @@global.gtid_binlog_state - and extracting
the domain id components from the intersection list items.
The new DELETE_DOMAIN_ID featured FLUSH continues to rotate binlog
omitting the deleted domains from the active binlog file's Gtid_list.
Notice though when the command is ineffective - that none of requested to delete
domain exists in the binlog state - rotation does not occur.
Obsolete domain deletion is not harmful for connected slaves as long
as master side binlog files *purge* is synchronized with FLUSH-DELETE_DOMAIN_ID.
The slaves must have the last event from purged files processed as usual,
in order not to bump later into requesting a gtid from a file which
was already gone.
While the command is not replicated (as ordinary FLUSH BINLOG LOGS is)
slaves, even though having extra domains, won't suffer from reconnection errors
thanks to master-slave gtid connection protocol allowing the master
to be ignorant about a gtid domain.
Should at failover such slave to be promoted into master role it may run
the ex-master's
FLUSH BINARY LOGS DELETE_DOMAIN_ID=(list-of-domains)
to clean its own binlog state.
NOTES.
suite/perfschema/r/start_server_low_digest.result
is re-recorded as consequence of internal parser codes changes.
A reference to a CTE may occur not in the master of the CTE
specification. In this case if the reference to the CTE is
the first one the specification should be detached from its
master and attached to the referencing select.
Also fixed the TYPE column in the lines of the EXPLAIN output
created for CTE tables.
- Fix win64 pointer truncation warnings
(usually coming from misusing 0x%lx and long cast in DBUG)
- Also fix printf-format warnings
Make the above mentioned warnings fatal.
- fix pthread_join on Windows to set return value.
Make st_select_lex::set_explain_type() take into account that JOIN_TABs
it is traversing may be also post-join aggregation JOIN_TABs (which
have pos_in_table_list=NULL, etc).
This patch fills in a serious flaw in the
code that supports condition pushdown into
materialized views / derived tables.
If a predicate happened to contain a reference
to a mergeable view / derived table and it does
not depended directly on the target materialized
view / derived table then the predicate was not
considered as a subject to pusdown to this view
/ derived table.
Significantly reduce the amount of InnoDB, XtraDB and Mariabackup
code changes by defining pfs_os_file_t as something that is
transparently compatible with os_file_t.
Do not silence uncertain cases, or fix any bugs.
The only functional change should be that ha_federated::extra()
is not calling DBUG_PRINT to report an unhandled case for
HA_EXTRA_PREPARE_FOR_DROP.
Do not silence uncertain cases, or fix any bugs.
The only functional change should be that ha_federated::extra()
is not calling DBUG_PRINT to report an unhandled case for
HA_EXTRA_PREPARE_FOR_DROP.
At some conditions the function opt_sum_query() can apply MIN/MAX
optimizations to to Item_sum objects of a select These optimizations
becomes invalid if this select is the subquery of an IN subquery
predicate that is converted to a EXISTS subquery. Thus in this case
the MIX/MAX optimizations that have been applied in opt_sum_query()
must be rolled back.
This bug appeared in 5.3 when the code for the cost base choice between
materialization and in-to-exists transformation of non-correlated
IN subqueries was introduced. Before this code in-to-exists
transformations were always performed before the call of opt_sum_query().
Cherry-pick: f4a0af070ce49abae60040f6f32e1074309c27fb
Author: Dmitry Lenev <dmitry.lenev@oracle.com>
Date: Mon Jul 25 16:06:52 2016 +0300
Fix for bug #16672723 "CAN'T FIND TEMPORARY TABLE".
Attempt to execute prepared CREATE TABLE SELECT statement which used
temporary table in the subquery in FROM clause and stored function
failed with unwarranted ER_NO_SUCH_TABLE error. The same happened
when such statement was used in stored procedure and this procedure
was re-executed.
The problem occurred because execution of such prepared statement/its
re-execution as part of stored procedure incorrectly set
Query_table_list::query_tables_own_last marker, indicating the last
table which is directly used by statement. As result temporary table
used in the subquery was treated as indirectly used/belonging to
prelocking list and was not pre-opened by open_temporary_tables()
call before statement execution. Thus causing ER_NO_SUCH_TABLE errors
since our code assumes that temporary tables need to be correctly
pre-opened before statement execution.
This problem became visible only in version 5.6 after patches related to
bug 11746602/27480 "EXTEND CREATE TEMPORARY TABLES PRIVILEGE TO ALLOW
TEMP TABLE OPERATIONS" since they have introduced pre-opening of temporary
tables for statements.
Incorrect setting of Query_table_list::query_tables_own_last happened
in LEX::first_lists_tables_same() method which is called by CREATE TABLE
SELECT implementation as part of LEX::unlink_first_table(), which temporary
excludes table list element for table being created from the query table
list before handling SELECT part.
LEX::first_lists_tables_same() tries to ensure that global table list of
the statement starts with the first table list element from the first
statement select. To do this it moves such table list element to the head
of the global table list. If this table happens to be last directly-used
table for the statement, query_tables_own_last marker is pointing to it.
Since this marker was not updated when table list element was moved we
ended up with all tables except the first table separated by it as if
they were not directly used by statement (i.e. belonged to prelocked
tables list).
This fix changes code of LEX::first_lists_tables_same() to update
query_tables_own_last marker in cases when it points to the table
being moved. It is set to the table which precedes table being moved
in this case.
