Bug #20662 "Infinite loop in CREATE TABLE IF NOT EXISTS ... SELECT
with locked tables"
Bug #20903 "Crash when using CREATE TABLE .. SELECT and triggers"
Bug #24738 "CREATE TABLE ... SELECT is not isolated properly"
Bug #24508 "Inconsistent results of CREATE TABLE ... SELECT when
temporary table exists"
Deadlock occured when one tried to execute CREATE TABLE IF NOT
EXISTS ... SELECT statement under LOCK TABLES which held
read lock on target table.
Attempt to execute the same statement for already existing
target table with triggers caused server crashes.
Also concurrent execution of CREATE TABLE ... SELECT statement
and other statements involving target table suffered from
various races (some of which might've led to deadlocks).
Finally, attempt to execute CREATE TABLE ... SELECT in case
when a temporary table with same name was already present
led to the insertion of data into this temporary table and
creation of empty non-temporary table.
All above problems stemmed from the old implementation of CREATE
TABLE ... SELECT in which we created, opened and locked target
table without any special protection in a separate step and not
with the rest of tables used by this statement.
This underminded deadlock-avoidance approach used in server
and created window for races. It also excluded target table
from prelocking causing problems with trigger execution.
The patch solves these problems by implementing new approach to
handling of CREATE TABLE ... SELECT for base tables.
We try to open and lock table to be created at the same time as
the rest of tables used by this statement. If such table does not
exist at this moment we create and place in the table cache special
placeholder for it which prevents its creation or any other usage
by other threads.
We still use old approach for creation of temporary tables.
Note that we have separate fix for 5.0 since there we use slightly
different less intrusive approach.
Bug #20662 "Infinite loop in CREATE TABLE IF NOT EXISTS ... SELECT
with locked tables"
Bug #20903 "Crash when using CREATE TABLE .. SELECT and triggers"
Bug #24738 "CREATE TABLE ... SELECT is not isolated properly"
Bug #24508 "Inconsistent results of CREATE TABLE ... SELECT when
temporary table exists"
Deadlock occured when one tried to execute CREATE TABLE IF NOT
EXISTS ... SELECT statement under LOCK TABLES which held
read lock on target table.
Attempt to execute the same statement for already existing
target table with triggers caused server crashes.
Also concurrent execution of CREATE TABLE ... SELECT statement
and other statements involving target table suffered from
various races (some of which might've led to deadlocks).
Finally, attempt to execute CREATE TABLE ... SELECT in case
when a temporary table with same name was already present
led to the insertion of data into this temporary table and
creation of empty non-temporary table.
All above problems stemmed from the old implementation of CREATE
TABLE ... SELECT in which we created, opened and locked target
table without any special protection in a separate step and not
with the rest of tables used by this statement.
This underminded deadlock-avoidance approach used in server
and created window for races. It also excluded target table
from prelocking causing problems with trigger execution.
The patch solves these problems by implementing new approach to
handling of CREATE TABLE ... SELECT for base tables.
We try to open and lock table to be created at the same time as
the rest of tables used by this statement. If such table does not
exist at this moment we create and place in the table cache special
placeholder for it which prevents its creation or any other usage
by other threads.
We still use old approach for creation of temporary tables.
Also note that we decided to postpone introduction of some tests
for concurrent behaviour of CREATE TABLE ... SELECT till 5.1.
The main reason for this is absence in 5.0 ability to set @@debug
variable at runtime, which can be circumvented only by using several
test files with individual .opt files. Since the latter is likely
to slowdown test-suite unnecessary we chose not to push this tests
into 5.0, but run them manually for this version and later push
their optimized version into 5.1
When using GROUP_CONCAT with ORDER BY, a tree is used for the sorting, as
opposed to normal nested loops join used when there is no ORDER BY.
The tree traversal that generates the result counts the lines that have been
cut down. (as they get cut down to the field's max_size)
But the check of that count was before the tree traversal, so no
warning was generated if the output is truncated.
Fixed by moving the check to after the tree traversal.
Bug occurs in INSERT IGNORE ... SELECT ... ON DUPLICATE KEY UPDATE
statements, when SELECT returns duplicated values and UPDATE clause
tries to assign NULL values to NOT NULL fields.
NOTE: By current design MySQL server treats INSERT IGNORE ... ON
DUPLICATE statements as INSERT ... ON DUPLICATE with update of
duplicated records, but MySQL manual lacks this information.
After this fix such behaviour becomes legalized.
The write_record() function was returning error values even within
INSERT IGNORE, because ignore_errors parameter of
the fill_record_n_invoke_before_triggers() function call was
always set to FALSE. FALSE is replaced by info->ignore.
TIMESTAMP field when no value has been provided.
The LOAD DATA sets the current time in the TIMESTAMP field with
CURRENT_TIMESTAMP default value when the field is detected as a null.
But when the LOAD DATA command loads data from a file that doesn't contain
enough data for all fields then the rest of fields are simply set to null
without any check. This leads to no value being inserted to such TIMESTAMP
field.
Now the read_sep_field() and the read_fixed_length() functions set current
time to the TIMESTAMP field with CURRENT_TIMESTAMP default value in all cases
when a NULL value is loaded to the field.
