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3. writing MySql plugins for the information schema
3. writing MySql plugins for the information schema
3. writing MySql plugins for the information schema
3. writing MySql plugins for the information schema
3. writing MySql plugins for the information schema
3. writing MySql plugins for the information schema
3. writing MySql plugins for the information schema
3. writing MySql plugins for the information schema
3. writing MySql plugins for the information schema
3. writing MySql plugins for the information schema
3. writing MySql plugins for the information schema
3. writing MySql plugins for the information schema
3. writing MySql plugins for the information schema
3. writing MySql plugins for the information schema
3. writing MySql plugins for the information schema
3. writing MySql plugins for the information schema
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3. writing MySql plugins for the information schema

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  • 1. Roland Bouman http://rpbouman.blogspot.com/ 1 Writing MySQL 5.1 Information Schema Plugins
  • 2. Roland Bouman http://rpbouman.blogspot.com/ 2 Tasks Before Implementing Information Schema Plugins ● Standard headers – <stdlib.h>, <ctype.h> ● Non-specific MySQL headers: – <mysql_version.h>, <mysql/plugin.h> ● Extra headers for Information Schema plug-ins – <mysql_priv.h> – <my_global.h> – <my_dir.h>
  • 3. Roland Bouman http://rpbouman.blogspot.com/ 3 Implementing Information Schema Plug-ins ● Setup the column layout – Defines the column names and data types ● Implement a fill function – Is called to fill the (in-memory) table ● Hook up table object with colum layout and fill function – Plug-in initialization function
  • 4. Roland Bouman http://rpbouman.blogspot.com/ 4 Information Schema Plug-ins: Column Layout ● Array of ST_FIELD_INFO – typedef struct st_field_info – Defined in sql/table.h typedef struct st_field_info { const char* field_name; uint field_length; enum enum_field_types field_type; int value; uint field_flags; const char* old_name; uint open_method; } ST_FIELD_INFO;
  • 5. Roland Bouman http://rpbouman.blogspot.com/ 5 ST_FIELD_INFO members (1/2) ● field_name: Column name ● field_length: – String type columns: #characters – Non-string types: 'display length' ● field_type: type constant – enum_field_types (mysql_com.h) ● field_flags: – MY_I_S_MAYBE_NULL – MY_I_S_UNSIGNED
  • 6. Roland Bouman http://rpbouman.blogspot.com/ 6 ST_FIELD_INFO members (2/2) ● open_method: (sql/table.h) – SKIP_OPEN_TABLE – OPEN_FRM_ONLY – OPEN_FULL_TABLE ● old_name: Column name for SHOW command ● value: ??
  • 7. Roland Bouman http://rpbouman.blogspot.com/ 7 Information Schema Plug-ins: Column Layout Example ● information_schema.SCHEMATA ST_FIELD_INFO schema_fields_info[]= { {"CATALOG_NAME", FN_REFLEN, MYSQL_TYPE_STRING, 0, 1, 0, SKIP_OPEN_TABLE}, {"SCHEMA_NAME", NAME_CHAR_LEN, MYSQL_TYPE_STRING, 0, 0, "Database", SKIP_OPEN_TABLE}, {"DEFAULT_CHARACTER_SET_NAME", MY_CS_NAME_SIZE, MYSQL_TYPE_STRING, 0, 0, 0, SKIP_OPEN_TABLE}, {"DEFAULT_COLLATION_NAME", MY_CS_NAME_SIZE, MYSQL_TYPE_STRING, 0, 0, 0, SKIP_OPEN_TABLE}, {"SQL_PATH", FN_REFLEN, MYSQL_TYPE_STRING, 0, 1, 0, SKIP_OPEN_TABLE}, {0, 0, MYSQL_TYPE_STRING, 0, 0, 0, SKIP_OPEN_TABLE} }
  • 8. Roland Bouman http://rpbouman.blogspot.com/ 8 Information Schema Plug-ins: Fill Function (1/4) ● fill_table( THD *thd, TABLE_LIST *tables, COND *cond ) ● THD: thread descriptor (sql/sql_class.h) ● TABLE_LIST: (sql/sql_table.h) – List of struct st_table (a.k.a. TABLE) ● COND: Condition.
  • 9. Roland Bouman http://rpbouman.blogspot.com/ 9 Information Schema Plug-ins: Fill Function (2/4) ● Grab first table from the list: TABLE *table= (TABLE *)tables->table; ● Store data in fields: table->field[i]->store(...); ● Store row in table schema_table_store_record(thd, table);
  • 10. Roland Bouman http://rpbouman.blogspot.com/ 10 Information Schema Plug-ins: Fill Function (3/4) ● schema_table_store_record( THD *thd , TABLE *table ) ● Forward declaration in mysql_priv.h ● Defined in sql/sql_show.cc
  • 11. Roland Bouman http://rpbouman.blogspot.com/ 11 Information Schema Plug-ins: Fill Function (4/4) int myplugin_fill_table( THD *thd, TABLE_LIST *tables, COND *cond ){ int status; CHARSET_INFO *scs= system_charset_info; TABLE *table= (TABLE *)tables->table; for ( ... ) { // table->field[0]->store( ... ); ... table->field[X]->store( ... ); status= schema_table_store_record( thd, table ); } return status; }
  • 12. Roland Bouman http://rpbouman.blogspot.com/ 12 Information Schema Plug-ins: Hookup Column Layout and Filler ● plugin_init static int myplugin_init(void *p) { ST_SCHEMA_TABLE *schema= (ST_SCHEMA_TABLE *)p; schema->fields_info= myplugin_field_info; schema->fill_table= myplugin_fill_table; return 0; }
  • 13. Roland Bouman http://rpbouman.blogspot.com/ 13 Information Schema Plug-ins: ST_SCHEMA_TABLE ● ST_SCHEMA_TABLE a.k.a st_schema_table typedef struct st_schema_table { const char* table_name; ST_FIELD_INFO *fields_info; TABLE *(*create_table)(THD *thd, TABLE_LIST *table_list); int (*fill_table) ( THD *thd, TABLE_LIST *tables, COND *cond); int (*old_format) ( THD *thd, struct st_schema_table *schema_table); int (*process_table) ( THD *thd, TABLE_LIST *tables,TABLE *table, bool res, LEX_STRING *db_name, LEX_STRING *table_name); int idx_field1, idx_field2; bool hidden; uint i_s_requested_object; } ST_SCHEMA_TABLE;
  • 14. Roland Bouman http://rpbouman.blogspot.com/ 14 Information Schema Plug-ins: Hookup Column Layout and Filler ● plugin_init static int myplugin_init(void *p) { ST_SCHEMA_TABLE *schema= (ST_SCHEMA_TABLE *)p; schema->fields_info= myplugin_field_info; schema->fill_table= myplugin_fill_table; return 0; }
  • 15. Roland Bouman http://rpbouman.blogspot.com/ 15 Information Schema Plug-ins: Hookup Column Layout and Filler ● plugin_init static int myplugin_init(void *p) { ST_SCHEMA_TABLE *schema= (ST_SCHEMA_TABLE *)p; schema->fields_info= myplugin_field_info; schema->fill_table= myplugin_fill_table; return 0; }
  • 16. Roland Bouman http://rpbouman.blogspot.com/ 16 Information Schema Plug-ins: Hookup Column Layout and Filler ● plugin_init static int myplugin_init(void *p) { ST_SCHEMA_TABLE *schema= (ST_SCHEMA_TABLE *)p; schema->fields_info= myplugin_field_info; schema->fill_table= myplugin_fill_table; return 0; }

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