Pushbuild fixes:
- Make MAX_SEL_ARGS smaller (even 16K records_in_range() calls is
more than it makes sense to do in typical cases)
- Don't call sel_arg->test_use_count() if we've already allocated
more than MAX_SEL_ARGs elements. The test will succeed but will take
too much time for the test suite (and not provide much value).
- Added PARAM::alloced_sel_args where we count the # of SEL_ARGs
created by SEL_ARG tree cloning operations.
- Made the range analyzer to shortcut and not do any more cloning
if we've already created MAX_SEL_ARGS SEL_ARG objects in cloning.
- Added comments about space complexity of SEL_ARG-graph
representation.
To correctly decide which predicates can be evaluated with a given table
the optimizer must know the exact set of tables that a predicate depends
on. If that mask is too wide (refer to non-existing tables) the optimizer
can erroneously skip a predicate.
One such case of wrong table usage mask were the aggregate functions.
The have a all-1 mask (meaning depend on all tables, including non-existent
ones).
Fixed by making a real used_tables mask for the aggregates. The mask is
constructed in the following way :
1. OR the table dependency masks of all the arguments of the aggregate.
2. If all the arguments of the function are from the local name resolution
context and it is evaluated in the same name resolution
context where it is referenced all the tables from that name resolution
context are OR-ed to the dependency mask. This is to denote that an
aggregate function depends on the number of rows it processes.
3. Handle correctly the case of an aggregate function optimization (such that
the aggregate function can be pre-calculated and made a constant).
Made sure that an aggregate function is never a constant (unless subject of a
specific optimization and pre-calculation).
One other flaw was revealed and fixed in the process : references were
not calling the recalculation method for used_tables of their targets.
A wrong order of statements in QUICK_GROUP_MIN_MAX_SELECT::reset
caused a crash when a query with DISTINCT was executed by a loose scan
for an InnoDB table that had been emptied.
This performance degradation for UPDATEs could be observed in the update
statements for which the search key cannot be converted to any valid
value of the type of the search column, like for a the condition
int_fld=99999999999999999999999999, though it can be guaranteed here
that there is no row with such a key value.
The bug could cause choosing a sub-optimal execution plan for
a single-table query if a unique index with many null keys were
defined for the table.
It happened because the code of the check_quick_keys function
made an assumption that any key may occur in an unique index
only once. Yet this is not true for keys with nulls that may
have multiple occurrences in the index.
Corrected spelling in copyright text
Makefile.am:
Don't update the files from BitKeeper
Many files:
Removed "MySQL Finland AB & TCX DataKonsult AB" from copyright header
Adjusted year(s) in copyright header
Many files:
Added GPL copyright text
Removed files:
Docs/Support/colspec-fix.pl
Docs/Support/docbook-fixup.pl
Docs/Support/docbook-prefix.pl
Docs/Support/docbook-split
Docs/Support/make-docbook
Docs/Support/make-makefile
Docs/Support/test-make-manual
Docs/Support/test-make-manual-de
Docs/Support/xwf
repair it
Multi-table delete that is optimized with QUICK_RANGE reports table
corruption.
DELETE statement must not use KEYREAD optimization, and sets
table->no_keyread to 1. This was ignored in QUICK_RANGE optimization.
With this fix QUICK_RANGE optimization honors table->no_keyread
value and does not enable KEYREAD when it is requested.
- Removed not used variables and functions
- Added #ifdef around code that is not used
- Renamed variables and functions to avoid conflicts
- Removed some not used arguments
Fixed some class/struct warnings in ndb
Added define IS_LONGDATA() to simplify code in libmysql.c
I did run gcov on the changes and added 'purecov' comments on almost all lines that was not just variable name changes
Fixed compiler warnings (detected by VC++):
- Removed not used variables
- Added casts
- Fixed wrong assignments to bool
- Fixed wrong calls with bool arguments
- Added missing argument to store(longlong), which caused wrong store method to be called.
statements
Currently the optimizer evaluates loose index scan only for top-level SELECT
statements
Extend loose index scan applicability by :
- Test the applicability of loose scan for each sub-select, instead of the
whole query. This change enables loose index scan for sub-queries.
- allow non-select statements with SELECT parts (like, e.g.
CREATE TABLE .. SELECT ...) to use loose index scan.
(Mostly in DBUG_PRINT() and unused arguments)
Fixed bug in query cache when used with traceing (--with-debug)
Fixed memory leak in mysqldump
Removed warnings from mysqltest scripts (replaced -- with #)
We miss some records sometimes using RANGE method if we have
partial key segments.
Example:
Create table t1(a char(2), key(a(1)));
insert into t1 values ('a'), ('xx');
select a from t1 where a > 'x';
We call index_read() passing 'x' key and HA_READ_AFTER_KEY flag
in the handler::read_range_first() wich is wrong because we have
a partial key segment for the field and might miss records like 'xx'.
Fix: don't use open segments in such a case.
When using index for group by and range access the server isolates
a set of ranges based on the conditions over the key parts of the
index used. Then it uses only the ranges over the GROUP BY fields to
jump from one group to another. Since the GROUP BY fields may form a
prefix over the index, we may use only a prefix of the ranges produced
by the range optimizer.
Each range contains a notion on whether it includes its border values.
The problem is that when using a range prefix, the last range is open
because it assumes that there is a range on the next keypart. Thus when
we use a prefix range as it is, it excludes all border values.
The solution is when ignoring the suffix of the range conditions
(to jump over the GROUP BY prefix only) the server must change the
remaining intervals so they always contain their borders, e.g.
if the whole range was :
(1,-inf) <= (<group_by_col>,<min_max_arg_col>) < (1, 3) we must make
(1) <= (<group_by_col>) <= (1) because (a,b) < (c1,c2) means :
a < c1 OR (a = c1 AND b < c2).
this key does not stop" (version for 5.0 only).
UPDATE statement which WHERE clause used key and which invoked trigger
that modified field in this key worked indefinetely.
This problem occured because in cases when UPDATE statement was
executed in update-on-the-fly mode (in which row is updated right
during evaluation of select for WHERE clause) the new version of
the row became visible to select representing WHERE clause and was
updated again and again.
We already solve this problem for UPDATE statements which does not
invoke triggers by detecting the fact that we are going to update
field in key used for scanning and performing update in two steps,
during the first step we gather information about the rows to be
updated and then doing actual updates. We also do this for
MULTI-UPDATE and in its case we even detect situation when such
fields are updated in triggers (actually we simply assume that
we always update fields used in key if we have before update
trigger).
The fix simply extends this check which is done in check_if_key_used()/
QUICK_SELECT_I::check_if_keys_used() routine/method in such way that
it also detects cases when field used in key is updated in trigger.
As nice side-effect we have more precise and thus more optimal
perfomance-wise check for the MULTI-UPDATE.
Also check_if_key_used()/QUICK_SELECT_I::check_if_keys_used() were
renamed to is_key_used()/QUICK_SELECT_I::is_keys_used() in order to
better reflect that boolean predicate.
Note that this check is implemented in much more elegant way in 5.1
Only MyISAM tables locked with LOCK TABLES ... WRITE were affected.
A query that is optimized with index_merge doesn't reflect rows
inserted within LOCK TABLES.
MyISAM doesn't flush a state within LOCK TABLES. index_merge
optimization creates a copy of the handler, which thus gets
outdated MyISAM state.
New handler->clone() method is introduced to fix this problem.
For non-MyISAM storage engines it allocates a handler and opens
it with ha_open(). For MyISAM it additionally copies MyISAM state
pointer to cloned handler.
when a range condition use an invalid DATETIME constant.
Now we do not use invalid DATETIME constants to form end keys for
range intervals: range analysis just ignores predicates with such
constants.
