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| template<class T , class JsonObjectPtr , class... Args> |
| static bool | AddMemberToObject (const JsonObjectPtr &obj, const char *alias, Args &&...ctor_args) |
| | Convenience function to add a json field. More...
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| template<class T , class... Args> |
| static bool | AddElementToArray (const unique_ptr< Json_array > &array, Args &&...ctor_args) |
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| static bool | PrintRanges (const QUICK_RANGE *const *ranges, unsigned num_ranges, const KEY_PART_INFO *key_part, bool single_part_only, const unique_ptr< Json_array > &range_array, string *ranges_out) |
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| static unique_ptr< Json_object > | ExplainAccessPath (const AccessPath *path, const AccessPath *materialized_path, JOIN *join, bool is_root_of_join, unique_ptr< Json_object > root_obj) |
| | Convert the AccessPath into a Json object that represents the EXPLAIN output This Json object may in turn be used to output in whichever required format. More...
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| static unique_ptr< Json_object > | ExplainNoAccessPath (const THD::Query_plan *query_plan) |
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| static unique_ptr< Json_object > | AssignParentPath (AccessPath *table_path, const AccessPath *materialized_path, unique_ptr< Json_object > materialized_obj, JOIN *join) |
| | AccessPath objects of type TEMPTABLE_AGGREGATE, MATERIALIZE, and MATERIALIZE_INFORMATION_SCHEMA_TABLE represent a materialized set of rows. More...
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| static double | GetJSONDouble (const Json_object *obj, const char *key) |
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| static bool | IsCoveringIndexScan (const KEY &key, const TABLE &table) |
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| static bool | AddTableInfoToObject (Json_object *obj, const TABLE *table) |
| | Add table name, schema name, and list of used columns for the specified table to the JSON object. More...
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| static bool | SetIndexInfoInObject (string *str, const char *json_index_access_type, const char *prefix, const TABLE &table, const KEY &key, uint n_key_columns, const char *index_access_type, const string lookup_condition, const string *ranges_text, unique_ptr< Json_array > range_arr, bool reverse, Item *pushed_idx_cond, Json_object *obj) |
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| string | JoinTypeToString (JoinType join_type) |
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| string | HashJoinTypeToString (RelationalExpression::Type join_type, string *explain_json_value) |
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| static bool | AddSubqueryPaths (const Item *item_arg, const char *source_text, vector< ExplainChild > *children) |
| | For each Item_subselect descendant of 'item_arg', add the corresponding root AccessPath object to 'children'. More...
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| static bool | GetAccessPathsFromSelectList (JOIN *join, vector< ExplainChild > *children) |
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| static unique_ptr< Json_object > | ExplainMaterializeAccessPath (const AccessPath *path, JOIN *join, unique_ptr< Json_object > ret_obj, vector< ExplainChild > *children, bool explain_analyze) |
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| static bool | ExplainIndexSkipScanAccessPath (Json_object *obj, const AccessPath *path, JOIN *join, string *description) |
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| static bool | ExplainGroupIndexSkipScanAccessPath (Json_object *obj, const AccessPath *path, JOIN *join, string *description) |
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| static bool | AddChildrenFromPushedCondition (const TABLE &table, vector< ExplainChild > *children) |
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| static bool | AddChildrenToObject (Json_object *obj, vector< ExplainChild > children, JOIN *parent_join, bool parent_is_root_of_join, string alias) |
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| static unique_ptr< Json_object > | ExplainQueryPlan (const AccessPath *path, THD::Query_plan const *query_plan, JOIN *join, bool is_root_of_join) |
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| static bool | AddPathCosts (const AccessPath *path, const AccessPath *materialized_path, Json_object *obj, bool explain_analyze) |
| | Append the various costs. More...
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| static unique_ptr< Json_object > | SetObjectMembers (unique_ptr< Json_object > ret_obj, const AccessPath *path, const AccessPath *materialized_path, JOIN *join, vector< ExplainChild > *children) |
| | Given a json object, update it's appropriate json fields according to the input path. More...
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| std::string | PrintQueryPlan (THD *ethd, const THD *query_thd, Query_expression *unit) |
| | Print out an access path and all of its children (if any) in a tree. More...
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| std::string | PrintQueryPlan (int level, AccessPath *path, JOIN *join, bool is_root_of_join) |
| | For debugging purposes. More...
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| static string | GetForceSubplanToken (const Json_object *obj, const string &children_digest) |
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| string | GetForceSubplanToken (AccessPath *path, JOIN *join) |
| | Generate a digest based on the subplan that the given access path represents. More...
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AccessPath objects of type TEMPTABLE_AGGREGATE, MATERIALIZE, and MATERIALIZE_INFORMATION_SCHEMA_TABLE represent a materialized set of rows.
These materialized AccessPaths have a another path member (called table_path) that iterates over the materialized rows.
So codewise, table_path is a child of the materialized path, even if it is logically the parent, as it consumes the results from the materialized path. For that reason, we present table_path above the materialized path in 'explain' output (
- See also
- AddPathCost for details).
This function therefore sets the JSON object for the materialized path to be the leaf descendant of the table_path JSON object. (Note that in some cases table_path does not operate directly on materialized_path. Instead, table_path is the first in a chain of paths where the final path is typically a TABLE_SCAN of REF access path that the iterates over the materialized rows.)
- Parameters
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| table_path | the head of the chain of paths that iterates over the materialized rows. |
| materialized_path | if (the leaf descendant of) table_path iterates over the rows from a MATERIALIZE path, then 'materialized_path' is that path. Otherwise it is nullptr. |
| materialized_obj | the JSON object describing the materialized path. |
| join | the JOIN to which 'table_path' belongs. |
- Returns
- the JSON object describing table_path.
Generate a digest based on the subplan that the given access path represents.
This can be used by developers to force a given subplan, to investigate e.g. whether a given choice is actually faster in practice, force-apply a plan from the old join optimizer (or at least the types of subplans that are ever considered; e.g. aggregation through temporary tables are not) into the hypergraph join optimizer (to see how it's costed), or whether a given plan is even generated. If DEBUG contains force_subplan_0x<token>, subplans with the given token are unconditionally preferred over all others.
The token returned is “0x<digest>”, where <digest> is the first 64 bits of the SHA-256 sum of this string:
desc1,desc2,...,[child1_desc:]0xchild1,[child2_desc:]0xchild2,<more children>
where desc1, desc2, etc. are the description lines given by EXPLAIN, and 0xchild1 is the token for children. The normal way to generate such tokens is to use SET DEBUG='+d,subplan_tokens' and look at the EXPLAIN FORMAT=tree, but in a pinch, you can also write them by hand and use sha256sum or a similar tool.
Only the hypergraph join optimizer honors token preferences, but EXPLAIN FORMAT=tree shows computed tokens for both optimizers.
1.9.2