CreateLookupVindex is a VReplication workflow used to create and backfill a lookup Vindex automatically for a table that already exists, and may have a significant amount of data in it already.

Internally, the CreateLookupVindex process uses VReplication for the backfill process, until the lookup Vindex is "in sync". Then the normal process for adding/deleting/updating rows in the lookup Vindex via the usual transactional flow when updating the "owner" table for the Vindex takes over.

In this guide, we will walk through the process of using the CreateLookupVindex workflow, and give some insight into what happens underneath the covers.

The CreateLookupVindex vtctl client command has the following syntax:

CreateLookupVindex -- [--cells=<source_cells>] [--continue_after_copy_with_owner=false] [--tablet_types=<source_tablet_types>] <keyspace> <json_spec>

• <json_spec>: Use the lookup Vindex specified in <json_spec> along with VReplication to populate/backfill the lookup Vindex from the source table.
• <keyspace>: The Vitess keyspace we are creating the lookup Vindex in. The source table is expected to also be in this keyspace.
• --tablet-types: Provided to specify the tablet types (e.g. PRIMARY, REPLICA, RDONLY) that are acceptable as source tablets for the VReplication stream(s) that this command will create. If not specified, the tablet type used will default to the value of the vttablet --vreplication_tablet_type flag value, which defaults to in_order:REPLICA,PRIMARY.
• --cells: By default VReplication streams, such as used by CreateLookupVindex, will not cross cell boundaries. If you want the VReplication streams to source their data from tablets in cells other than the local cell, you can use the --cells option to specify a comma-separated list of cells (see VReplication tablet selection).
• --continue_after_copy_with_owner: By default, when an owner is provided in the <json_spec>, the VReplication streams will stop after the backfill completes. Specify this flag if you don't want this to happen. This is useful if, for example, the owner table is being migrated from an unsharded keyspace to a sharded keyspace using MoveTables.

The <json_spec> describes the lookup Vindex to be created, and details about the table it is to be created against (on which column, etc.). However, you do not have to specify details about the actual lookup table, Vitess will create that automatically based on the type of the column you are creating the Vindex column on, etc.