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MySQL Bypass Project Initial Change [non-RocksDB part]
Summary: MySQL bypass infrastructure change 1. Adds a new hton override `handlerton::handle_single_table_select` to allow hijacking of SELECT statement execution from any storage engine. 2. Add lex parsing for bypass hints in optimizer hint style /*+ bypass */ and /*+ no_bypass */ 3. MyRocks overrides handle_single_table_select but does nothing and simply fallback. This is a port from from bypass feature branch - change #1 of 3. I'm planning to port the changes in the following order: 1. MySQL lexer + SELECT hijacking (this one). 2. SELECT Statement parsing and checking 3. Execution of SELECT statement in bypass Reference Patch: facebook/mysql-5.6@2d19dc0 ----- Porting Notes: * The entry points have changed due to MySQL 8.0 refactoring to SELECT path, and now it is in `Sql_cmd_dml::execute_inner`. I'll also see if overriding the entire execute would be better but this should be good enough for now. * The check for whether we should go to bypass handler is mostly the same, except st_select_lex_t is now SELECT_LEX. * The lex parsing for hints was mostly ported as-is. I was also debating whether I should just use optimizer hints instead of hacking the lexer, but decided against using optimizer hint for now so that migration from 5.6 will be easier. We can migrate to optimizer hint once 8.0 migration is complete. Differential Revision: D22807040 --------------------------------------------------------------------------------------------- [bypass] MySQL bypass change #2 - SELECT parsing [non-RocksDB part] Summary: This is change #2 that ports the SELECT statement parsing from feature-myrocks-bypass branch, including: 1. select_parser class that parses SELECT statements and validates the scenarios are supported, and error with proper message if not supported 2. You can control bypass policy with rocksdb_select_bypass_policy variable = 0 (ALWAYS OFF) / 1 (ALWAYS ON) / 2 (OPT IN) / 3 (OPT OUT). 3. A few metrics for number of SELECT bypass statements executed/rejected (due to not supported) /failed (something wrong in execution) At this point this only dumps the SELECT statement parsed results without doing anything useful. The next change will be porting the query plan execution and point/range query execution part. Please ignore the unused attributes for now - they'll be removed in next change once the execution part is ported. Reference Patch: facebook/mysql-5.6@e79b20a facebook/mysql-5.6@8072e3d --- Porting Notes: There are a lot of small changes in this area but nothing too bad: * Some bypass scenarios no longer fail or fail with different error message because of the new parse tree -> AST conversion process. For example, `SELECT *` now works correctly * st_select_lex_t -> SELECT_LEX, and many members has changed name, such as where -> where_cond() * protocol usage has changed to start_row, store, end_row in 8.0, which is much better. * thd->query() is now a LEX_STRING * SELECT option check (such as SELECT_DISTINCT) now uses active_options() and only check for SELECT_DISTINCT as there seems to be default value being set most likely due to side effect of having more parse tree processing being done. I checked the flags and it looks like only SELECT_DISTINCT are interesting and needs to be blocked. * SELECT INTO OUTFILE check is changed to use results->needs_file_priviledge * True/False const are now represented as Item_func_true/Item_func_false. For now I'm over-generalizing to functions that are const, and expect val_int/etc would do the right thing Reviewed By: luqun Differential Revision: D22808305 ----------------------------------------------------------------------------------------------- Introduce base select parser class Summary: To make it easier to add a new bypass rpc parser into existing bypass implementation (nosql_access.cc), and make minimum change to bypass engine while adding a bypass rpc parser, I introduced a new base class, base_select_parser. It includes all essential members and methods for parsing bypass sq/rpc queries. Existing bypass sql parser (select_parser) and a new bypass rpc parser (not included in this diff) inherits the base function. Bypass RPC reference diff: D30493654 Reviewed By: yizhang82 Differential Revision: D31870628
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