7.3.23. io_flush

7.3.23.1. Summary

New in version 5.0.5.

io_flush flushes all changes in memory to disk explicitly. Normally, you don't need to use io_flush explicitly. Because flushing is done automatically by OS. And flushing by OS is effective.

You need to use io_flush explicitly when your system may often crash unexpectedly or you may not shutdown your Groonga process in a normal way. (For example, using shutdown is a normal shutdown process.) It's better that you use io_flush after you change your Groonga database for the case. Here are commands that change your Groonga database:

If you're using scorer parameter in select to change existing column values, select is added to the above list.

Note that io_flush may be a heavy process. If there are many changes in memory, flushing them to disk is a heavy process.

7.3.23.2. Syntax

This command takes three parameters.

All parameters are optional:

io_flush [target_name=null]
         [recursive=yes]
         [only_opened=no]

New in version 7.0.4: only_opened is added.

7.3.23.3. Usage

You can flush all changes in memory to disk with no arguments:

Execution example:

io_flush
# [[0, 1337566253.89858, 0.000355720520019531], true]

If you know what is changed, you can narrow flush targets. Here is a correspondence table between command and flush targets.

Command Flush targets io_flush arguments
load and delete

Target table and its columns.

If there are one or more reference columns in these columns, referenced tables are also flush targets.

If there are one or more indexed columns in these columns, tables of corresponding index columns and corresponding index columns are also flush targets.

Table and its columns:

io_flush --target_name TABLE_NAME

A referenced table:

io_flush --target_name REFERENCED_TABLE_NAME --recursive no

A table of an index column:

io_flush --target_name TABLE_NAME_OF_INDEX_COLUMN --recursive no

An index column:

io_flush --target_name TABLE_NAME_OF_INDEX_COLUMN.INDEX_COLUMN
truncate

Target table and its columns.

If there are one or more reference columns in these columns, referenced tables are also flush targets.

If there are one or more indexed columns in these columns, tables of corresponding index columns and corresponding index columns are also flush targets.

Database is also flush target.

Table and its columns:

io_flush --target_name TABLE_NAME

A referenced table:

io_flush --target_name REFERENCED_TABLE_NAME --recursive no

A table of an index column:

io_flush --target_name TABLE_NAME_OF_INDEX_COLUMN --recursive no

An index column:

io_flush --target_name TABLE_NAME_OF_INDEX_COLUMN.INDEX_COLUMN

Database:

io_flush --recursive no
table_create Target table and database.

Table:

io_flush --target_name TABLE_NAME

Database:

io_flush --recursive no
table_remove, table_rename and logical_table_remove Database.

Database:

io_flush --recursive no
column_create Target column and database.

Table:

io_flush --target_name TABLE_NAME.COLUMN_NAME

Database:

io_flush --recursive no
column_remove and column_rename Database.

Database:

io_flush --recursive no
plugin_register and plugin_unregister Database.

Database:

io_flush --recursive no

7.3.23.4. Parameters

This section describes all parameters.

7.3.23.4.1. Required parameters

There is no required parameter.

7.3.23.4.2. Optional parameters

There are optional parameters.

7.3.23.4.2.1. target_name

Specifies a flush target object name. Target object is one of database, table or column.

If you omit this parameter, database is flush target object:

Execution example:

io_flush
# [[0, 1337566253.89858, 0.000355720520019531], true]

If you specify table name, the table is flush target object:

Execution example:

table_create Users TABLE_HASH_KEY ShortText
# [[0, 1337566253.89858, 0.000355720520019531], true]
io_flush --target_name Users
# [[0, 1337566253.89858, 0.000355720520019531], true]

If you specify column name, the column is flush target object:

Execution example:

column_create Users age COLUMN_SCALAR UInt8
# [[0, 1337566253.89858, 0.000355720520019531], true]
io_flush --target_name Users.age
# [[0, 1337566253.89858, 0.000355720520019531], true]

7.3.23.4.2.2. recursive

Specifies whether child objects of the flush target object are also flush target objects.

Child objects of database is all tables and all columns.

Child objects of table is all its columns.

Child objects of column is nothing.

If you specify yes to only_opened, recursive is ignored.

recursive value must be yes or no. yes means that all of the specified flush target object and child objects are flush target objects. no means that only the specified flush target object is flush target object.

The following io_flush flushes all changes in database, all tables and all columns:

Execution example:

io_flush --recursive yes
# [[0, 1337566253.89858, 0.000355720520019531], true]

The following io_flush flushes all changes only in database:

Execution example:

io_flush --recursive no
# [[0, 1337566253.89858, 0.000355720520019531], true]

If you specify other value (not yes neither no) or omit recursive parameter, yes is used.

yes is used in the following case because invalid recursive argument is specified:

Execution example:

io_flush --recursive invalid
# [[0, 1337566253.89858, 0.000355720520019531], true]

yes is used in the following case because recursive parameter isn't specified:

Execution example:

io_flush
# [[0, 1337566253.89858, 0.000355720520019531], true]

7.3.23.4.2.3. only_opened

New in version 7.0.4.

Specifies whether opened objects are only flushed.

If there is only one process that changes the target database, flush performance will be improved by specifying yes to only_opened. It skips needless flushes.

You can't specify target_name with only_opened option. If you specify target_name, only_opened is ignored.

If you specify yes to only_opened, recursive is ignored.

only_opened value must be yes or no. yes means that opened objects are only flushed. no means that all target objects are flushed even they aren't opened.

The following io_flush flushes all changes in database, all tables and all columns:

Execution example:

io_flush --only_opened yes
# [[0, 1337566253.89858, 0.000355720520019531], true]

7.3.23.5. Return value

The command returns true as body on success such as:

[HEADER, true]

If the command fails, error details are in HEADER.

See Output format for HEADER.