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Displaying posts with tag: parser (reset)

MySQL 5.7: only_full_group_by Improved, Recognizing Functional Dependencies, Enabled by Default!
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Here’s an account of recent work which has kept me busy and excited for a few months. For those unfamiliar with the only_full_group_by sql mode, let me provide some context. I’ll use the world database, which can be downloaded from this MySQL Documentation page. You can find details on how to install the database on the same page. We have a table of countries and a table of languages spoken in each country. It’s a 1-to-N relationship: …

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The Query Rewrite Plugins
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Why Query Rewrites?

Now that the cost model project is progressing, most of you are going to notice execution plan changes. In the vast majority of the cases, the changes will be for the better, and some bugs with a long history will finally be closed. In some cases, however, you will notice that your queries run slower. This is inevitable: even if the MySQL optimizer is doing a much better job with the information it has, it may still be the case that the information was incomplete and that the best plan was, in fact, found by not trusting …

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SQL parser refactoring in 5.7.4 LAB release
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We are refactoring the SQL parser: the sql_yacc.yy file and friends.

Refactoring the parser consists of a base task that provides the common framework for refactoring, and several follow-up tasks to refactor individual types of SQL statements. We have already completed two follow-up tasks: one to refactor SELECT statements, and another to refactor SET …

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