Donot reserve memory for non-fixed type columns in decodeAndSquash (#7418)

[ti-chi-bot]

This is an automated cherry-pick of #7418

What problem does this PR solve?

Issue Number: close #7416

Problem Summary:

What is changed and how it works?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Fix the issue that the query might use much larger memories than actual needed when Join build side data is very large and contains many small-size string type columns. 

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• xzhangxian1008
• yibin87

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[yibin87]

LGTM

[yibin87]

/merge

[ti-chi-bot]

@yibin87: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

You only need to trigger /merge once, and if the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 449893e

[yibin87]

/run-integration-test

[ti-chi-bot]

@ti-chi-bot: Your PR was out of date, I have automatically updated it for you.

At the same time I will also trigger all tests for you:

/run-all-tests

trigger some heavy tests which will not run always when PR updated.

If the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.