![]() ![]() In this case, the update will fall back to performing a full update, which means that it writes the whole new JSON value to the database. If the JSON value being updated is something like, there would not be enough room for the new name. Additionally, the JSON value being updated must already have a member called name, and there must be enough existing space in the JSON value to hold the new name. ![]() This update can be performed as a partial update because it takes a JSON column ( json_col), modifies one of its members, and then stores it into the same column as it reads from ( json_col). UPDATE t SET json_col = JSON_SET(json_col, '$.name', 'Knut') WHERE id = 123 Instead, MySQL analyzes each UPDATE statement and enables it when it can, so your application will benefit from the improvements automatically if the UPDATE statements already are on a form that is recognized as partial update.Ī simple example is the following statement, which changes the name attribute in a JSON value: There is no new syntax for partial update. So what do you have to do to get the benefit of partial update of JSON values in your application? In many cases nothing, apart from upgrading to MySQL 8.0. This can result in significantly reduced disk I/O and network I/O for update-intensive workloads. The patches are also used by row-based replication to reduce the amount of binary log shipped to the replication slave, if the proper option is enabled. The storage engine can use these patches to write the minimal amount of data. What’s new in MySQL 8.0, is that MySQL is able to recognize that certain UPDATE statements can modify JSON documents in place, and for these statements it will provide the storage engine with patches that describe the modifications. Before, in MySQL 5.7, whenever you made a change to a stored JSON document, the full new JSON document would be written to the database, even if the update just changed a few bytes in the document. MySQL 8.0 introduces partial update of JSON values, which is a nice performance improvement for applications that frequently update small portions of large JSON documents. ![]()
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