Cost of updating secondary indices

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Cost of updating secondary indices - dating agency perth australia

PDF (US Ltr) - 35.5Mb PDF (A4) - 35.5Mb PDF (RPM) - 34.6Mb EPUB - 8.7Mb HTML Download (TGZ) - 8.5Mb HTML Download (Zip) - 8.5Mb HTML Download (RPM) - 7.3Mb Eclipse Doc Plugin (TGZ) - 9.3Mb Eclipse Doc Plugin (Zip) - 11.5Mb Man Pages (TGZ) - 202.0Kb Man Pages (Zip) - 307.3Kb Info (Gzip) - 3.3Mb Info (Zip) - 3.3Mb My SQL Backup and Recovery My SQL Globalization My SQL Information Schema My SQL Installation Guide My SQL and Linux/Unix My SQL and OS X My SQL Partitioning My SQL Performance Schema My SQL Replication Using the My SQL Yum Repository My SQL Restrictions and Limitations Security in My SQL My SQL and Solaris Building My SQL from Source Starting and Stopping My SQL My SQL Tutorial My SQL and Windows My SQL Cluster NDB 7.5 supports secondary indexes on generated virtual columns. A secondary index may be created on one or more virtual columns or on a combination of virtual columns and non-generated virtual columns.

If the index is a covering index (one that includes all the columns retrieved by a query), generated column values are retrieved from materialized values in the index structure instead of computed generated columns, which are materialized in the clustered index, resulting in larger tables that require more disk space and memory.If a secondary index is not defined on a virtual column, there are additional costs for reads, as virtual column values must be computed each time the column's row is examined.Values of an indexed virtual column are MVCC-logged to avoid unnecessary recomputation of generated column values during rollback or during a purge operation.The data length of logged values is limited by the index key limit of 767 bytes for row formats.Adding or dropping a secondary index on a virtual column is an in-place operation.Prior to 5.7.16, a foreign key constraint cannot reference a secondary index defined on a generated virtual column.

In My SQL 5.7.13 and earlier, columns cannot be indexed directly.To create an index that references such a column indirectly, you can define a generated column that extracts the information that should be indexed, then create an index on the generated column, as shown in this example: *************************** 1.row *************************** id: 1 select_type: SIMPLE table: jemp partitions: NULL type: range possible_keys: i key: i key_len: 5 ref: NULL rows: 2 filtered: 100.00 Extra: Using where 1 row in set, 1 warning (0.00 sec) mysql *************************** 1.row *************************** Level: Note Code: 1003 Message: /* select#1 */ select json_unquote(json_extract(`test`.`jemp`.`c`,'$.name')) AS `name` from `test`.`jemp` where (`test`.`jemp`.`g` (We have wrapped the output from the last statement in this example to fit the viewing area.See Section 9.3.9, “Optimizer Use of Generated Column Indexes”, for the statements used to create and populate the table just shown.) In My SQL 5.7.9 and later, you can use *************************** 1.row *************************** id: 1 select_type: SIMPLE table: jemp partitions: NULL type: range possible_keys: i key: i key_len: 5 ref: NULL rows: 2 filtered: 100.00 Extra: Using where; Using filesort 1 row in set, 1 warning (0.00 sec) mysql function (Section 13.16.3, “Functions That Search JSON Values”) for additional information and examples.

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