*: fix the estimation error on normal column when collation enabled #18104
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
winoros
added
type/bugfix
winoros
requested review from
eurekaka,
wjhuang2016 and
lzmhhh123
and removed request for
a team
|
/rebuild |
Codecov Report
@@ Coverage Diff @@
## master #18104 +/- ##
===========================================
Coverage 79.5315% 79.5315%
===========================================
Files 535 535
Lines 144725 144725
===========================================
Hits 115102 115102
Misses 20353 20353
Partials 9270 9270 |
|
/run-integration-common-test tikv=pr/8105 |
|
/run-common-test |
|
/run-integration-common-test tikv=pr/8105 |
|
/merge |
|
/run-all-tests tikv=pr/8105 |
|
/run-integration-br-tests tikv=pr/8105 |
|
/run-integration-br-tests tikv=pr/8105 |
|
/run-integration-br-tests tikv=pr/8105 tiflash=master |
|
/run-unit-test |
|
/run-unit-test |
1 similar comment
|
/run-unit-test |
ti-srebot
pushed a commit
to ti-srebot/tidb
that referenced
this pull request
Jul 1, 2020
Signed-off-by: ti-srebot <ti-srebot@pingcap.com>
|
cherry pick to release-4.0 in PR #18311 |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
What problem does this PR solve?
Issue Number: close #14689
Problem Summary:
For index, its key is already generated by the sort key by the collation information. And when we query the index estimation, we also use
EncodeKeywhich will first convert the column value to sort key then encode it. So it's automatically correct for index without any additional change.But for a column, when sampling we use its original value thus when query it with count-min sketch or histogram. We'll get a wrong answer since the order information is lost.
What is changed and how it works?
What's Changed:
For tikv part, use the sort key generated by the collation as the sampling data. tikv/tikv#8105
And when querying, convert to sort key first.
How it Works:
Related changes
Check List
Tests
Side effects
Release note