UPDATE
This is a legacy Apache Ignite documentation
The new documentation is hosted here: https://ignite.apache.org/docs/latest/
Update data in a table.
UPDATE tableName [[AS] newTableAlias]
SET {{columnName = {DEFAULT | expression}} [,...]} |
{(columnName [,...]) = (select)}
[WHERE expression][LIMIT expression]
Parameters
table- the name of the table to be updated.columnName- the name of a column to be updated with a value fromSETclause.
Description
UPDATE command alters existing entries stored in a table.
Since Ignite stores all the data in a form of key-value pairs, all the UPDATE statements are finally transformed into a set of key-value operations.
Initially, SQL engine generates and executes a SELECT query based on the UPDATE WHERE clause and only after that it modifies the existing values that satisfy the clause result.
The modification is performed via cache.invokeAll(...) operation. Basically, it means that once the result of the SELECT query is ready, SQL engine will prepare a number of EntryProcessors and will execute all of them using cache.invokeAll(...) operation. While the data is being modified using EntryProcessors, additional checks are performed to make sure that nobody has interfered between the SELECT and the actual update.
Refer to concurrent modifications section that explains how SQL engine solves concurrency issues.
Primary Keys Updates
Ignite does not allow updating a primary key because the latter defines a partition the key and its value belong to statically. While the partition with all its data can change several cluster owners, the key always belongs to a single partition all the times. The partition is calculated using a hash function applied to the key's value.
Considering this, if a key needs to be updated it has to be removed and inserted consequently.
Examples
Update column name of an entry:
UPDATE Person SET name = 'John Black' WHERE id = 2;
Update Person table with the data taken from Account table:
UPDATE Person p SET name = (SELECT a.first_name FROM Account a WHERE a.id = p.id)
Note
Java, .NET, C++ users can execute UPDATE queries using native APIs:
See Also
Updated about 5 years ago