MDEV-17631 select_handler for a full query pushdown
Interfaces + Proof of Concept for federatedx with test cases.
The interfaces have been developed for integration of ColumnStore engine.
ANALYZE and ANALYZE FORMAT=JSON structures are changed in the way that they
show additional information when rowid filter is used:
- r_selectivity_pct - the observed filter selectivity
- r_buffer_size - the size of the rowid filter container buffer
- r_filling_time_ms - how long it took to fill rowid filter container
New class Rowid_filter_tracker was added. This class is needed to collect data
about how rowid filter is executed.
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.
Counter for select numbering made stored with the statement (before was global)
So now it does have always accurate value which does not depend on
interruption of statement prepare by errors like lack of table in
a view definition.
Most "new" failures fixed in the following files:
- sql_select.cc
- item.cc
- item_func.cc
- opt_subselect.cc
Other things:
- Allocate udf_handler strings in mem_root
- Required changes in sql_string.h
- Add mem_root as argument to some new [] calls
- Mark udf_handler strings as thread specific
- Removed some comment blocks with code
- Tabular EXPLAIN now prints "RECURSIVE UNION".
- There is a basic implementation of EXPLAIN FORMAT=JSON.
- it produces "recursive_union" JSON struct
- No other details or ANALYZE support, yet.
Fixes over the original patch:
- Fix variable/class/other names
- Fix the JSON output to be in line with the output of other JSON
constructs we produce
- Remove ANALYZE's timing code off the the execution path of regular
SELECTs.
- Improve the tracker that tracks counts/execution times of SELECTs or
DML statements:
= regular execution just increments counters
= ANALYZE will also collect timings.
Show total execution time (r_total_time_ms) for various parts of the
query:
1. time spent in SELECTs
2. time spent reading rows from storage engines
#2 currently gets the data from P_S.
