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

Introduced 2 new variables #6159

Merged
merged 2 commits into from
Aug 20, 2021
Merged

Introduced 2 new variables #6159

Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
405b487
Introduced 2 new variables
hfxsd Aug 13, 2021
d9b686f
Apply suggestions from code review
hfxsd Aug 20, 2021
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
14 changes: 14 additions & 0 deletions system-variables.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -996,6 +996,20 @@ For a system upgraded to v5.0 from an earlier version, if you have not modified
- This variable is used to set whether the optimizer executes the optimization operation of pushing down the aggregate function to the position before Join, Projection, and UnionAll.
- When the aggregate operation is slow in query, you can set the variable value to ON.

### `tidb_opt_limit_push_down_threshold`
hfxsd marked this conversation as resolved.
Show resolved Hide resolved

- Scope: SESSION | GLOBAL
- Default value: `100`
- Range: `[0, 2147483647]`
- This variable is used to push down the Limit and TopN operators to the threshold in TiKV.
hfxsd marked this conversation as resolved.
Show resolved Hide resolved
- If the value of Limit or TopN is less than or equal to this threshold, then the Limit and TopN operators are forcibly pushed down to TiKV. This variable provides a solution when Limit or TopN cannot be pushed down due to estimation errors.
hfxsd marked this conversation as resolved.
Show resolved Hide resolved

### `tidb_opt_enable_correlation_adjustment`
hfxsd marked this conversation as resolved.
Show resolved Hide resolved

- Scope: SESSION | GLOBAL
- Default value: `ON`
- This variable is used for the optimizer whether to enable the method that estimates the number of rows based on column order correlation
hfxsd marked this conversation as resolved.
Show resolved Hide resolved

### tidb_opt_correlation_exp_factor

- Scope: SESSION | GLOBAL
Expand Down