my_like_range*() can create longer keys than Field::char_length().
This caused warnings during print_range().
Fix:
Suppressing warnings in print_range().
When executing a statement of the form
SELECT AGGR_FN(DISTINCT c1, c2,..,cn) FROM t1,
where AGGR_FN is an aggregate function such as COUNT(), AVG() or SUM(),
and a unique index exists on table t1 covering some or all of the
columns (c1, c2,..,cn), the retrieved values are inherently unique.
Consequently, the need for de-duplication imposed by the DISTINCT
clause can be eliminated, leading to optimization of aggregation
operations.
This optimization applies under the following conditions:
- only one table involved in the join (not counting const tables)
- some arguments of the aggregate function are fields
(not functions/subqueries)
This optimization extends to queries of the form
SELECT AGGR_FN(c1, c2,..,cn) GROUP BY cx,..cy
when a unique index covers some or all of the columns
(c1, c2,..cn, cx,..cy)
This bug caused server crash when processing a multi-update statement that
used views if optimizer tracing was enabled.
The bug was introduced in the patch for MDEV-30539 that could incorrectly
detect the most top level selects of queries if views were used in them.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
EXPLAIN EXTENDED for an UPDATE/DELETE/INSERT/REPLACE statement did not
produce the warning containing the text representation of the query
obtained after the optimization phase. Such warning was produced for
SELECT statements, but not for DML statements.
The patch fixes this defect of EXPLAIN EXTENDED for DML statements.
MDEV-30668 Set function aggregated in outer select used in view definition
This patch fixes two bugs concerning views whose specifications contain
subqueries with set functions aggregated in outer selects.
Due to the first bug those such views that have implicit grouping were
considered as mergeable. This led to wrong result sets for selects from
these views.
Due to the second bug the aggregation select was determined incorrectly and
this led to bogus error messages.
The patch added several test cases for these two bugs and for four other
duplicate bugs.
The patch also enables view-protocol for many other test cases.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
(Patch from Monty, slightly amended)
Fix rowid filtering optimization in best_access_path():
== Ref access + rowid filtering ==
The cost computations compare #records and index-only scan cost
(keyread_tmp) to find out the per-record advantage one will get if
they skip reading full table record.
The computations produce wrong result when:
- the #records are "clipped down" with s->worst_seeks or
thd->variables.max_seeks_for_key. keyread_tmp is not clipped
this way so the numbers are not comparable.
- access_factor is negative. This means index_only read is
cheaper than non-index-only read.
This patch makes the optimizer not to consider Rowid Filtering in
such cases.
The decision is logged in the Optimizer Trace using
"rowid_filter_skipped" name.
== Range access + rowid filtering ==
when considering to use Rowid Filter with range access, do multiply
keyread_tmp by record_count. That way, it is comparable with the
range access's estimate, which is multiplied by record_count.
make_join_select() calls const_cond->val_int(). There are edge cases
where const_cond may have a not-yet optimized subquery.
(The subquery will have used_tables() covered by join->const_tables. It
will still have const_item()==false, so other parts of the optimizer
will not try to evaluate it. We should probably mark such subqueries
as constant but that is outside the scope of this MDEV)
This enables optimizer_trace output for the next SQL command.
Identical as if one would have done:
- Store value of @@optimizer_trace
- Set @optimizer_trace="enabled=on"
- Run query
- SELECT * from OPTIMIZER_TRACE
- Restore value of @@optimizer_trace
This is a great time saver when one wants to quickly check the optimizer
trace for a query in a mtr test.
if a query used no fields from an I_S table, we were creating a temp
table with one, first, field (as a table cannot have zero fields),
with its length truncated to 1.
Now - force also this dummy field to be a normal field, not a BLOB
Make sure to initialize members of TABLE::reginfo when TABLE::init is called. In this case the problem
was that table->reginfo.join_tab was set for the SELECT query and then was reused by the UPDATE query.
This case occurred only when the SELECT query had a degenerate join.
KEY_MULTI_RANGE::range_flag does not have correct flag bits for
per-endpoint flags (NEAR_MIN, NEAR_MAX, NO_MIN_RANGE, NO_MAX_RANGE).
It only has bits for flags that describe both endpoints.
So
- Document this.
- Switch optimizer trace to using {start|end}_key.flag values, instead.
This fixes the bug.
- Switch records_in_column_ranges() to doing that too. (This used to
work, because KEY_MULTI_RANGE::range_flag had correct flag value
for the last key component, and EITS only uses one-component
pseudo-indexes)
sprintf() format of double changed from '%lg' to '%-.11lg'
The change was to make it easier to read optimizer trace output
with tables that has millions of records.
