Optimizer hints #3474
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Optimizer hints #3474
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- Lex_ident_cli* into a new file sql/lex_ident_cli.h - Lex_ident_sys* into a new file sql/lex_ident_sys.h - Well_formed_prefix into include/m_ctype.h This change is needed to the optimizer hint parser coming soon.
Implementing a recursive descent parser for optimizer hints.
This commit introduces:
- the infrastructure for optimizer hints;
- hints for join buffering: BNL(), NO_BNL(), BKA(), NO_BKA();
- NO_ICP() hint for disabling index condition pushdown;
- MRR(), MO_MRR() hint for multi-range reads control;
- NO_RANGE_OPTIMIZATION() for disabling range optimization;
- QB_NAME() for assigning names for query blocks.
- Using Lex_ident_sys to scan identifiers, like the SQL parser does.
This fixes handling of double-quote-delimited and backtick-delimited identifiers,
as well as handling of non-ASCII identifiers.
Unescaping and converting from the client character set to the system
character set is now done using Lex_ident_cli_st and Lex_ident_sys,
like it's done in the SQL tokenizer/parser.
Adding helper methods to_ident_cli() and to_ident_sys()
in Optimizer_hint_parser::Token.
- Fixing the hint parser to report a syntax error when an empty identifiers:
SELECT /*+ BKA(``) */ * FROM t1;
- Moving a part of the code from opt_hints_parser.h to opt_hints_parser.cc
Moving these method definitions:
- Optimizer_hint_tokenizer::find_keyword()
- Optimizer_hint_tokenizer::get_token()
to avoid huge pieces of the code in the header file.
- A Lex_ident_cli_st cleanup
Fixing a few Lex_ident_cli_st methods to return Lex_ident_cli_st &
instead of void, to use them easier in the caller code.
- Fixing the hint parser to display the correct line number
Adding a new data type Lex_comment_st
(a combination of LEX_CSTRING and a line number)
Using it in sql_yacc.yy
- Getting rid of redundant dependencies on sql_hints_parser.h
Moving void LEX::resolve_optimizer_hints() from sql_lex.h to sql_lex.cc
Adding a class Optimizer_hint_parser_output, deriving from
Optimizer_hint_parser::Hint_list. Fixing the hint parser to
return a pointer to an allocated instance of Optimizer_hint_parser_output
rather than an instance of Optimizer_hint_parser::Hint_list.
This allows to use a forward declaration of Optimizer_hint_parser_output
in sql_lex.h and thus avoid dependencies on sql_hints_parser.h.
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Forbid adding optimizer hints to view definitions. In the case when optimizer hints are added to the view definition at a `CREATE (OR REPLACE) VIEW`/`ALTER VIEW` statement, a warning is generated and the hints are ignored. This commit also disables ps-protocol for test cases where `Unresolved table/index name` warnings are generated. The reason for this is such warnings are generated during both PREPARE and EXECUTE stages. Since opt_hints.test has `--enable_prepare_warnings`, running it with `--ps-protocol` causes duplication of warning messages
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join_cache_level=0 disables join cache buffers, but the hint BNL() now allows to employ BNL(H) buffers for particular tables or query blocks. This commit also adds a number of test cases including OUTER JOINs to make sure hints do not break the rules of join buffers application
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Provide the possibility to add optimizer hints to statements in MySQL-compatible format:
Implemented so far:
Release Notes
TODO: What should the release notes say about this change?
Include any changed system variables, status variables or behaviour. Optionally list any https://mariadb.com/kb/ pages that need changing.
How can this PR be tested?
TODO: modify the automated test suite to verify that the PR causes MariaDB to behave as intended.
Consult the documentation on "Writing good test cases".
If the changes are not amenable to automated testing, please explain why not and carefully describe how to test manually.
Basing the PR against the correct MariaDB version
PR quality check