(Variant 3, initial variant was by Rex Jonston)
A LEFT JOIN with a constant as a column of the inner table produced wrong
query result if the optimizer had to write the inner table column into a
temp table. Query pattern:
SELECT ...
FROM (SELECT /*non-mergeable select*/
FROM t1 LEFT JOIN (SELECT 'Y' as Val) t2 ON ...) as tbl
Fixed this by adding Item_direct_view_ref::save_in_field() which follows
the pattern of Item_direct_view_ref's save_org_in_field(),
save_in_result_field() and val_XXX() functions:
* call check_null_ref() and handle NULL value
* if we didn't get a NULL-complemented row, call Item_direct_ref's function.
Starting from 10.3, the optimizer is able to detect that entire outer join
nests are constants (because of "Impossible ON") and remove them (see
mark_join_nest_as_const)
However, this was not properly accounted for in NESTED_JOIN structure
and the way check_interleaving_with_nj() uses its n_tables member to
check if the join prefix order is allowed.
(The result was that the optimizer could conclude that no join prefix is
allowed and fail an assertion)
- multi_range_read_info_const now uses the new records_in_range interface
- Added handler::avg_io_cost()
- Don't calculate avg_io_cost() in get_sweep_read_cost if avg_io_cost is
not 1.0. In this case we trust the avg_io_cost() from the handler.
- Changed test_quick_select to use TIME_FOR_COMPARE instead of
TIME_FOR_COMPARE_IDX to align this with the rest of the code.
- Fixed bug when using test_if_cheaper_ordering where we didn't use
keyread if index was changed
- Fixed a bug where we didn't use index only read when using order-by-index
- Added keyread_time() to HEAP.
The default keyread_time() was optimized for blocks and not suitable for
HEAP. The effect was the HEAP prefered table scans over ranges for btree
indexes.
- Fixed get_sweep_read_cost() for HEAP tables
- Ensure that range and ref have same cost for simple ranges
Added a small cost (MULTI_RANGE_READ_SETUP_COST) to ranges to ensure
we favior ref for range for simple queries.
- Fixed that matching_candidates_in_table() uses same number of records
as the rest of the optimizer
- Added avg_io_cost() to JT_EQ_REF cost. This helps calculate the cost for
HEAP and temporary tables better. A few tests changed because of this.
- heap::read_time() and heap::keyread_time() adjusted to not add +1.
This was to ensure that handler::keyread_time() doesn't give
higher cost for heap tables than for normal tables. One effect of
this is that heap and derived tables stored in heap will prefer
key access as this is now regarded as cheap.
- Changed cost for index read in sql_select.cc to match
multi_range_read_info_const(). All index cost calculation is now
done trough one function.
- 'ref' will now use quick_cost for keys if it exists. This is done
so that for '=' ranges, 'ref' is prefered over 'range'.
- scan_time() now takes avg_io_costs() into account
- get_delayed_table_estimates() uses block_size and avg_io_cost()
- Removed default argument to test_if_order_by_key(); simplifies code
Change the defaults:
-histogram_size=0
+histogram_size=254
-histogram_type=SINGLE_PREC_HB
+histogram_type=DOUBLE_PREC_HB
Adjust the testcases:
- Some have ignorable changes in EXPLAIN outputs and
more counter increments due to EITS table reads.
- Testcases that meaningfully depend on the old defaults
are changed to use the old values.
This patch contains a full implementation of the optimization
that allows to use in-memory rowid / primary filters built for range
conditions over indexes. In many cases usage of such filters reduce
the number of disk seeks spent for fetching table rows.
In this implementation the choice of what possible filter to be applied
(if any) is made purely on cost-based considerations.
This implementation re-achitectured the partial implementation of
the feature pushed by Galina Shalygina in the commit
8d5a11122c.
Besides this patch contains a better implementation of the generic
handler function handler::multi_range_read_info_const() that
takes into account gaps between ranges when calculating the cost of
range index scans. It also contains some corrections of the
implementation of the handler function records_in_range() for MyISAM.
This patch supports the feature for InnoDB and MyISAM.
