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11.4.10. ConvertStringFromMySQL Filter

The ConvertStringFromMySQLFilter is designed to be used in replicators that are used in conjunction either with existing native MySQL to MySQL replication deployments, or clustering deployments where the replication has been configured to use native MySQL byte storage for strings. These are incompatible with heterogeneous deployments as the string is stored internally and in the THL in a format that is useful only within similarly configured replicators.

Conversion can be selected to happen for all valid columns (VARCHAR or CHAR column types only), or for selected columns within specific tables and schemas. All conversions are made with the relevant character set for the table and THL event.

Note

Conversion will not occur on incompatible columns. For example, conversion will not be applied to INT columns. This is the case even if the column has been explicitly set to convert the column.

Pre-configured filter name convertstringfrommysql
Classname com.continuent.tungsten.replicator.ConvertStringFromMySQLFilter
Property prefix Not defined
Stage compatibility any
tpm Option compatibility  
Data compatibility Row events only
Parameters
definitionsFile string support/filters-config/convertstringfrommysql.json JSON file containing the definition of which events and which tables to skip

Configuration of the filter is made using the generic JSON file, which supports both default options to happen for all tables not otherwise explicitly specified. The default JSON file converts all valid (VARCHAR or CHAR) column types only:

{
    "__default": {
        "*" : "true",
    },
    "SCHEMA" : {
        "TABLE" : {
            "COLUMN" : "true",
        },
    }
}

Warning

For column specific selection to work, the column names must be included within the THL. The colnames filter must have been enabled either before this filter, or on the extractor where the data was originally extracted.

The default section handles the default response when an explicit schema or table name does not appear. Further sections are then organised by schema, table and column name. Where the setting is true, conversion will take place. A false disables conversion.

To enable conversion on a single column DESCRIPTION within the SALES.INVOICE schema/table while disabling conversion on all other columns:

{
    "__default": {
        "*" : "false",
    },
    "SALES" : {
        "INVOICE" : {
            "DESCRIPTION" : "true",
        },
    }
}

To convert all compatible columns in all tables within a schema:

{
    "__default": {
        "*" : "false",
    },
    "SALES" : {
        "*" : {
            "*" : "true",
        },
    }
}

A primary use case for this filter is for cluster-slave replication from a cluster to a datawarehouse. For more details, please see Replicating from a Cluster to a Datawarehouse (in [Tungsten Clustering for MySQL 5.1 Manual]).

Source Cluster Example

For cluster-slave replication to a datawarehouse, the source cluster nodes must use ROW-based MySQL binary logging, and also must have two extractor filters enabled, colanmes and pkey.

For example, on every cluster node the lines below would be added to the /etc/tungsten/tungsten.ini file in the service stanza, then tpm update would be executed:

repl-svc-extractor-filters=colnames,pkey
property=replicator.filter.pkey.addColumnsToDeletes=true
property=replicator.filter.pkey.addPkeyToInserts=true

For staging deployments, prepend two hyphens to each line and include on the command line.

For more details about configuring the source cluster, please see ???.

Target Cluster-Slave Example

On the replication slave node, copy the convertstringfrommysql.json filter configuration sample file into the /opt/replicator/share directory then edit it to suit:

cp /opt/replicator/tungsten/tungsten-replicator/support/filters-config/convertstringfrommysql.json /opt/replicator/share/
vi /opt/replicator/share/convertstringfrommysql.json

Once the convertstringfrommysql JSON configuration file has been edited, update the /etc/tungsten/tungsten.ini file to add and configure the convertstringfrommysql filter.

For example, comfigure a service named omega on host6 to read from the cluster nodes defined by cluster-alias alpha.

[alpha]
topology=cluster-alias
master=host1
members=host1,host2,host3
thl-port=2112

[omega]
topology=cluster-slave
relay=host6
relay-source=alpha
repl-svc-remote-filters=convertstringfrommysql
property=replicator.filter.convertstringfrommysql.definitionsFile=/opt/replicator/share/convertstringfrommysql.json

For more details about configuring the target cluster-slave node, please see ???.