Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

optimizer-fix-controls: Add optimizer fix control 47400 for controlling zero estRows #18587

Open
wants to merge 10 commits into
base: master
Choose a base branch
from
+8 −0
Open

optimizer-fix-controls: Add optimizer fix control 47400 for controlling zero estRows #18587

Changes from all commits
Commits
Show all changes
10 commits
Select commit Hold shift + click to select a range
fe72790
Add fix control 47400
terry1purcell Aug 14, 2024
efae2e4
change to 8.4
terry1purcell Aug 14, 2024
0c3329a
formatting error
terry1purcell Aug 14, 2024
54fb4dd
Merge branch 'pingcap:master' into minonerow
terry1purcell Aug 20, 2024
89a2f44
review comments1
terry1purcell Aug 20, 2024
603994a
review comments2
terry1purcell Aug 28, 2024
558826c
Update optimizer-fix-controls.md
terry1purcell Sep 9, 2024
7bc4e80
Merge branch 'pingcap:master' into minonerow
terry1purcell Sep 10, 2024
4f88dfb
align with Chinese
Oreoxmt Sep 12, 2024
b3da029
Apply suggestions from code review
Oreoxmt Sep 25, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
8 changes: 8 additions & 0 deletions optimizer-fix-controls.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,14 @@ SET SESSION tidb_opt_fix_control = '44262:ON,44389:ON';
- This variable sets the threshold for the optimizer's heuristic strategy to select access paths. If the estimated rows for an access path (such as `Index_A`) is much smaller than that of other access paths (default `1000` times), the optimizer skips the cost comparison and directly selects `Index_A`.
- `0` means to disable this heuristic strategy.

### [`47400`](https://github.com/pingcap/tidb/issues/47400) <span class="version-mark">New in v8.4.0</span>

- Default value: `ON`
- Possible values: `ON`, `OFF`
- Due to challenges in accurately estimating the number of qualified rows for each plan step in a query plan, the optimizer might estimate a smaller value for `estRows`. This variable controls whether to limit the minimum value of `estRows`.
- `ON`: limits the minimum value of `estRows` to 1, which is the new behavior introduced in v8.4.0 and is consistent with other databases, such as Oracle and DB2.
- `OFF`: disables the minimum row estimate limit, which maintains the behavior consistent with versions before v8.4.0. In this case, `estRows` might be zero.

### [`52869`](https://github.com/pingcap/tidb/issues/52869) <span class="version-mark">New in v8.1.0</span>

- Default value: `OFF`
Expand Down
Loading