MDEV-8938 Server Crash on Update with joins
Make unique table check after setup_fields of update because unique table can materialize table and we do not need field resolving after materialization.
When CHANGE MASTER was executed as a PS, its attributes were wrongly
getting reset toward the end of PREPARE. As a result, the subsequent
executions had no effect. Fixed by making sure that the CHANGE MASTER
attributes are preserved during the lifetime of the PS.
Problem was in rewriting left expression which had 2 references on it. Solved with making subselect reference main.
Item_in_optimized can have not Item_in_subselect reference in left part so type casting with no check is dangerous.
Item::cols() should be checked after Item::fix_fields().
PROBLEMS
Description:- Server variable "--lower_case_tables_names"
when set to "0" on windows platform which does not support
case sensitive file operations leads to problems. A warning
message is printed in the error log while starting the
server with "--lower_case_tables_names=0". Also according to
the documentation, seting "lower_case_tables_names" to "0"
on a case-insensitive filesystem might lead to index
corruption.
Analysis:- The problem reported in the bug is:-
Creating an INNODB table 'a' and executing a query, "INSERT
INTO a SELECT a FROM A;" on a server started with
"--lower_case_tables_names=0" and running on a
case-insensitive filesystem leads innodb to flat spin.
Optimizer thinks that "a" and "A" are two different tables
as the variable "lower_case_table_names" is set to "0". As a
result, optimizer comes up with a plan which does not need a
temporary table. If the same table is used in select and
insert, a temporary table is needed. This incorrect
optimizer plan leads to infinite insertions.
Fix:- If the server is started with
"--lower_case_tables_names" set to 0 on a case-insensitive
filesystem, an error, "The server option
'lower_case_table_names'is configured to use case sensitive
table names but the data directory is on a case-insensitive
file system which is an unsupported combination. Please
consider either using a case sensitive file system for your
data directory or switching to a case-insensitive table name
mode.", is printed in the server error log and the server
exits.
DESCRIPTION
===========
Inability of mysql LOAD XML command to handle empty XML
tags i.e. <row><tag/></row>. Also the behaviour is wrong
and (different than above) when there is a space in empty
tag i.e. <row><tag /></row>
ANALYSIS
========
In read_xml() the case where we encounter a close tag ('/')
we're decreasing the 'level' blindly which is wrong.
Actually when its an without-space-empty-tag (succeeding
char is '>'), we need to skip the decrement. In other words
whenever we hit a close tag ('/'), decrease the 'level'
only when (i) It's not an (without space) empty tag i.e.
<tag/> or, (ii) It is of format <row col="val" .../>
FIX
===
The switch case for '/' is modified. We've removed the
blind decrement of 'level'. We do it only when its not an
without-space-empty-tag. Also we are setting 'in_tag' to
false to let program know that we're done reading current
tag (required in the case of format <row col="val" .../>)
VIEW
It appears that the code refactoring done as part of the
patch for the MySQL BUG#11749859 fixed this issue. This
issue is not reproducible on MySQL 5.5+ versions now.
As part of this patch, the test file "mysqldump.test" has
been updated to remove the comment which was referring to
the bug and also the line which suppresses the warning.
Analysis :
==========
During JOIN::prepare of sub-query which creates the
derived tables we call setup_procedure. Here we call
fix_fields for parameters of procedure clause. Calling
setup_procedure at this point may cause issue. If
sub-query is one of parameter being fixed it might
lead to complicated dependencies on derived tables
being prepared.
SOLUTION :
==========
In 5.6 with WL#6242, we have made procedure clause
parameters can only be NUM, so sub-queries are not
allowed as parameters. So in 5.5 we can block
sub-queries in procedure clause parameters.
This eliminates above conflicting dependencies.
THD::>save_prep_leaf_list was set to true by multi-table update
statements with mergeable selects and never reset.
Make every statement reset it at start.
Alternative fix that doesn't cause view.test crash in --ps:
Remember when Item_ref was fixed right in the constructor
and did not have a full Item_ref::fix_fields() call. Later
in PS/SP, after Item_ref::cleanup, we use this knowledge
to avoid doing full fix_fields() for items that were never
supposed to be fix_field'ed.
Simplify the test case.
execution of PS
GROUP_CONCAT() with ORDER BY column position may crash server on PS reexecution.
The problem was that arguments array of GROUP_CONCAT() was adjusted to point to
temporary elements (resolved ORDER BY fields) during first execution.
This patch expands rev. 08763096cb to restore original arguments array as well.
IS REJECTED.
Analysis
========
View creation with named columns over UNION is rejected.
Consider the following view definition:
CREATE VIEW v1 (fld1, fld2) AS SELECT 1 AS a, 2 AS b
UNION ALL SELECT 1 AS a, 1 AS a;
A 'duplicate column' error was reported due to the duplicate
alias name in the secondary SELECT. The VIEW column names
are either explicitly specified or determined from the
first SELECT (which can be auto generated if not specified).
Since a duplicate column name check was performed even
for the secondary SELECTs, an error was reported.
Fix
====
Check for duplicate column names only for the named
columns if specified or only for the first SELECT.
Analysis: At check_trx_exists function InnoDB allocates
a new trx if no trx is found from thd but this newly
allocated trx is not registered to thd. This is unsafe,
because nothing prevents InnoDB plugin from being uninstalled
while there's active transaction. This can cause crashes, hang
and any other odd behavior. It may also corrupt stack, as
functions pointers are not available after dlclose.
Fix: The fix is to use thd_set_ha_data() when
manipulating per-connection handler data. It does appropriate
plugin locking.
INCORRECT RESULTS
Issue:
-----
Updating varchar and text fields in the same update
statement can produce incorrect results. When a varchar
field is assigned to the text field and the varchar field
is then set to a different value, the text field's result
contains the varchar field's new value.
SOLUTION:
---------
Currently the blob type does not allocate space for the
string to be stored. Instead it contains a pointer to the
varchar string. So when the varchar field is changed as
part of the update statement, the value contained in the
blob also changes.
The fix would be to actually store the value by allocating
space for the blob's string. We can avoid allocating this
space when the varchar field is not being written into.
MULTIPLE THREADS
Description:- The utility "mysqlimport" does not use
multiple threads for the execution with option
"--use-threads". "mysqlimport" while importing multiple
files and multiple tables, uses a single thread even if the
number of threads are specified with "--use-threads" option.
Analysis:- This utility uses ifdef HAVE_LIBPTHREAD to check
for libpthread library and if defined uses libpthread
library for mutlithreaing. Since HAVE_LIBPTHREAD is not
defined anywhere in the source, "--use-threads" option is
silently ignored.
Fix:- "-DTHREADS" is set to the COMPILE_FLAGS which will
enable pthreads. HAVE_LIBPTHREAD macro is removed.
SELECT ... WHERE XX IN (SELECT YY)
this was transformed to something like:
SELECT ... WHERE IF_EXISTS(SELECT ... HAVING XX=YY)
The bug was that for normal execution XX was fixed in the original outer SELECT context while in PS it was fixed in the sub query context and this confused the optimizer.
Fixed by ensuring that XX is always fixed in the outer context.
This is MDEV-7601, including it's sub tasks MDEV-7594, MDEV-7555, MDEV-7590, MDEV-7581, MDEV-7589
The problem was that select_lex->non_agg_fields was not properly reset for re-execution and this caused an overwrite of a random memory position.
The fix was move non_agg_fields from select_lext to JOIN, which is properly reset.
Problem :
---------
Issue-1: The root cause for the issues is that (col1 > 1) is not a
valid partition function and we should have thrown error at much early
stage [partition_info::check_partition_info]. We are not checking
sub-partition expression when partition expression is NULL.
Issue-2: Potential issue for future if any partition function needs to
change item tree during open/fix_fields. We should release changed
items, if any, before doing closefrm when we open the partitioned table
during creation in create_table_impl.
Solution :
----------
1.check_partition_info() - Check for sub-partition expression even if no
partition expression.
[partition by ... columns(...) subpartition by hash(<expr>)]
2.create_table_impl() - Assert that the change list is empty before doing
closefrm for partitioned table. Currently no supported partition function
seems to be changing item tree during open.
Reviewed-by: Mattias Jonsson <mattias.jonsson@oracle.com>
RB: 9345
* add a test when server certificate is verified successfully
* one test with two combinations (instead of two tests)
* verbose tets: make it print what it is doing
* fix the test to work with yassl and no-ssl builds
"Range Checked for Each Record" should be only employed when the other
option would be cross-product join (i.e. the other option is so bad that
we hardly risk anything).
Previous logic was: use RCfER if there are no possible quick selects, or
quick select would read > 100 rows. Also, it didn't always work as
expected due to range optimizer changing table->quick_keys and us
looking at sel->quick_keys.
Another angle is that recent versions have enabled use of Join Buffering
in e.g. outer joins. This further reduces the range of cases where RCfER
should be used.
We are still unable to estimate the cost of RCfER with any precision, so
now changing the condition of "no quick select or quick->records> 100"
to a hopefully better condition "no quick select or quick would cost more
than full table scan".
Server may crash if sanity checks of COLUMN_GET() fail.
COLUMN_GET() description generator expects parent CAST item, which may not have
been created due to failure of sanity checks. Then further attempt to report
an error may crash the server.
Fixed COLUMN_GET() description generator to handle such case.
Factory timezone is supposed "For companies who don't want to put time zone
specification in their installation procedures. When users run date, they'll get
the message. Also useful for the "comp.sources" version."
This "message" is exposed as timezone abbreviation, which is supposed to be
short and thus may cause generated INSERT statements to fail.
Do not attempt to load Factory timezone.
