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https://dev.mysql.com/doc/internals/en/mysql-test-directory.html
The directory has a README file which explains how to run the tests, how to make new tests (in files with the filename extension *.test), and how to report errors. Primarily these are SQL scripts which try out a feature, output a result, and compare ...
https://dev.mysql.com/doc/internals/en/netware-directory.html
(.def is a common filename extension for "definition".) The three *.sql files are short scripts of SQL statements used in testing.
https://dev.mysql.com/doc/internals/en/nicely-displaying-trace.html
Also, have the @@end_markers_in_json variable off: when it's on, the trace is more human readable but not JSON compliant. Looking at a trace in the mysql command-line client can be cumbersome (though the pager less command makes it better). An ...
https://dev.mysql.com/doc/internals/en/not-so-fast-path.html
client wants to login with sha256_password, but doesn't have a matching scramble in the preceding initial packet and sends an empty password: 9e 00 00 01 85 a6 3f 00 00 00 00 01 21 00 00 00 ......?.....!... If the servers default auth method ...
https://dev.mysql.com/doc/internals/en/optimizer-and-relations.html
Otherwise, since (both conditions are indexed and have equal join type) pick a driver based on the first index that was created. An ANDed search has the form condition1 AND condition2, as in this example: WHERE column1 = 'x' AND column2 = 'y' Here, ...
https://dev.mysql.com/doc/internals/en/optimizer-constants-constant-tables.html
Although many queries have no constant-table references, it should be kept in mind that whenever the word constant is mentioned hereafter, it refers either to a literal or to the contents of a constant table. A MySQL constant is something more than ...
https://dev.mysql.com/doc/internals/en/optimizer-determining-join-type.html
The “Good” Execution Plan: Via the index, look up the rows which have indexed_column = 5. When evaluating a conditional expression, MySQL decides what join type the expression has. (Again: despite the word “join”, this applies for all ...
https://dev.mysql.com/doc/internals/en/optimizer-early-nulls-filtering.html
Suppose we have a join order such as this one: ..., tblX, ..., tblY, ... Suppose further that table tblY is accessed via ref or eq_ref access on tblY.key_column = tblX.column or, in the case of ref access using multiple key parts, via ... Here the ...
https://dev.mysql.com/doc/internals/en/optimizer-index-merge-join-type.html
7.2.2.5.1 Overview Index Merge is used when table condition can be converted to form: cond_1 OR cond_2 ... OR cond_N The conditions for conversion are that each cond_i can be used for a range scan, and no pair (cond_i, cond_j) uses the same index.
https://dev.mysql.com/doc/internals/en/optimizer-late-nulls-filtering.html
Suppose we have a query plan with table tblX being accessed via the ref access method: tblX.key_part1 = expr1 AND tblX.key_part2 = expr2 AND ... Before performing an index lookup, we determine whether any of the expri values is NULL. If it is, we ...