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Optimize performance of my_bitmap

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MDEV-33502 Slowdown when running nested statement with many partitions

This change was triggered to help some MariaDB users with close to
10000 bits in their bitmaps.

- Change underlaying storage to be 64 bit instead of 32bit.
  - This reduses number of loops to scan bitmaps.
  - This can cause some bitmaps to be 4 byte large.
- Ensure that all not used top-bits are always 0 (simplifes code as
  the last 64 bit storage is not a special case anymore).
- Use my_find_first_bit() to find the first set bit which is much faster
  than scanning trough things byte by byte and then bit by bit.

Other things:
- Added a bool to remember if my_bitmap_init() did allocate the bitmap
  array. my_bitmap_free() will only free arrays it did allocate.
  This allowed me to remove setting 'bitmap=0' before calling
  my_bitmap_free() for cases where the bitmap's where allocated externally.
- my_bitmap_init() sets bitmap to 0 in case of failure.
- Added 'universal' asserts to most bitmap functions.
- Change all remaining calls to bitmap_init() to my_bitmap_init().
  - To finish the change from 2014.
- Changed all usage of uint32 in my_bitmap.h to my_bitmap_map.
- Updated bitmap_copy() to handle bitmaps of different size.
- Removed const from bitmap_exists_intersection() as this caused casts
  on all usage.
- Removed not used function bitmap_set_above().
- Renamed create_last_word_mask() to create_last_bit_mask() (to match
  name changes in my_bitmap.cc)
- Extended bitmap-t with test for more bitmap functions.
This commit is contained in:
Monty
2024-02-18 17:30:01 +02:00
parent d4e1731fbc
commit b5d65fc105
18 changed files with 452 additions and 397 deletions
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4
sql/opt_range.cc
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@@ -3582,7 +3582,7 @@ bool calculate_cond_selectivity_for_table(THD *thd, TABLE *table, Item **cond)
table->reginfo.impossible_range= 0;
uint used_fields_buff_size= bitmap_buffer_size(table->s->fields);
uint32 *used_fields_buff= (uint32*)thd->alloc(used_fields_buff_size);
my_bitmap_map *used_fields_buff= (my_bitmap_map*)thd->alloc(used_fields_buff_size);
MY_BITMAP cols_for_indexes;
(void) my_bitmap_init(&cols_for_indexes, used_fields_buff, table->s->fields, 0);
bitmap_clear_all(&cols_for_indexes);
@@ -7439,7 +7439,7 @@ TRP_ROR_INTERSECT *get_best_covering_ror_intersect(PARAM *param,
(*scan)->used_fields_covered=
bitmap_bits_set(&(*scan)->covered_fields);
(*scan)->first_uncovered_field=
bitmap_get_first(&(*scan)->covered_fields);
bitmap_get_first_clear(&(*scan)->covered_fields);
}
my_qsort(ror_scan_mark, ror_scans_end-ror_scan_mark, sizeof(ROR_SCAN_INFO*),