Configuring search index joins

DataStax Enterprise supports solr_query joins on the partition key field (_partitionKey). By default, the solr_query join functionality is enabled and DSE indexes the partitioning columns in this additional field. This field, _partitionKey, increases search index size. Disabling joins can decrease the amount of disk space the search indexes uses.

Join settings in the schema

DESCRIBE ACTIVE SEARCH INDEX SCHEMA displays the schema settings of a search index. DSE hides the definition of the _partitionKey when joins are enabled.

If the schema contains a field named _partitionKey, support for joins is:

Enabled: attributes docValues and indexed are set to true. For example:

<field name="_partitionKey" **docValues="true"** **indexed="true"** stored="false" type="StrField"/>

Disabled: attributes docValues and indexed are set to false. For example:

<field **docValues="false"** **indexed="false"** multiValued="false" name="_partitionKey" omitNorms="true" **stored="false"** type="StrField"/>

If the schema contains no field definition for _partitionKey, then joins are enabled.

Prerequisite

This section uses the Term and phrase searches using the wikipedia demo.

Disable joins

Set the _partitionKey field attributes indexed and docValues to false.

About this task

Disable join on a search index by setting the _partitionKey field attributes indexed and docValues to false in the schema.

Procedure

Verify if schema has the field _partitionKey and fieldType StrField definitions.

DESCRIBE ACTIVE SEARCH INDEX SCHEMA ON wiki.solr;

The example search index has joins enabled with no _partitionKey definition:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<schema name="autoSolrSchema" version="1.5">
  <types>
    <fieldType class="org.apache.solr.schema.TextField" name="TextField">
      <analyzer>
        <tokenizer class="solr.StandardTokenizerFactory"/>
        <filter class="solr.LowerCaseFilterFactory"/>
      </analyzer>
    </fieldType>
    <fieldType class="org.apache.solr.schema.TrieDateField" name="TrieDateField"/>
    <fieldType class="org.apache.solr.schema.StrField" name="StrField"/>
  </types>
  <fields>
    <field indexed="true" multiValued="false" name="body" stored="true" type="TextField"/>
    <field docValues="true" indexed="true" multiValued="false" name="real_date" stored="true" type="TrieDateField"/>
    <field indexed="true" multiValued="false" name="title" stored="true" type="TextField"/>
    <field indexed="true" multiValued="false" name="id" stored="true" type="StrField"/>
    <field indexed="true" multiValued="false" name="date" stored="true" type="TextField"/>
  </fields>
  <uniqueKey>id</uniqueKey>
</schema>

If required, add the string type definition:
```
ALTER SEARCH INDEX SCHEMA ON wiki.solr
ADD types.fieldType[@class='org.apache.solr.schema.StrField', @name='StrField'];
```
The definition is added to the pending schema and is not immediately applied.

Define the partition key field:

If the search index already has the partition key field, change the indexed and docValues to false:

ALTER SEARCH INDEX SCHEMA ON wiki.solr
SET field[@name='_partitionKey']@docValues='false';
ALTER SEARCH INDEX SCHEMA ON wiki.solr
SET field[@name='_partitionKey']@indexed='false';

If the schema does not have a _partitionKey definition, add one to override the default settings:
```
ALTER SEARCH INDEX SCHEMA ON wiki.solr
ADD fields.field[@name='_partitionKey', @type='StrField', @docValues='false', @indexed='false'];
```
The type definition StrField is also required.

Verify that the schema definition was correctly modified:

DESCRIBE PENDING SEARCH INDEX SCHEMA ON wiki.solr;

For example, a simple table with three fields and a single partition key:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<schema name="autoSolrSchema" version="1.5">
  <types>
    <fieldType class="org.apache.solr.schema.TextField" name="TextField">
      <analyzer>
        <tokenizer class="solr.StandardTokenizerFactory"/>
        <filter class="solr.LowerCaseFilterFactory"/>
      </analyzer>
    </fieldType>
    <fieldType class="org.apache.solr.schema.TrieDateField" name="TrieDateField"/>
    <fieldType class="org.apache.solr.schema.StrField" name="StrField"/>
  </types>
  <fields>
    <field indexed="true" multiValued="false" name="body" stored="true" type="TextField"/>
    <field docValues="true" indexed="true" multiValued="false" name="real_date" stored="true" type="TrieDateField"/>
    <field indexed="true" multiValued="false" name="title" stored="true" type="TextField"/>
    <field indexed="true" multiValued="false" name="id" stored="true" type="StrField"/>
    <field indexed="true" multiValued="false" name="date" stored="true" type="TextField"/>
    <field docValues="false" indexed="false" name="_partitionKey" type="StrField"/>
  </fields>
  <uniqueKey>id</uniqueKey>
</schema>

Reload the schema to make it active:
```
RELOAD SEARCH INDEX ON wiki.solr;
```

Optional, rebuild the search index:

REBUILD SEARCH INDEX ON wiki.solr;

Rebuilding from CQL regenerates the index from the existing data on all search nodes, which use significant resources and is not required when disabling joins. When no rebuild command is executed after a schema change, new data in the field is not be duplicated and indexed. Use dsetool rebuild_indexes to regenerate the index on a node-by-node basis.

Start cqlsh on a node that is running DSE Search.

Set the docValues and indexed attributes to true:

ALTER SEARCH INDEX SCHEMA ON wiki.solr
SET field[@name='_partitionKey']@docValues='true';
ALTER SEARCH INDEX SCHEMA ON wiki.solr
SET field[@name='_partitionKey']@indexed='true';

Verify that the schema definition was correctly modified:

DESCRIBE PENDING SEARCH INDEX SCHEMA ON wiki.solr;

For example, a simple table with three fields and a single partition key:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<schema name="autoSolrSchema" version="1.5">
  <types>
    <fieldType class="org.apache.solr.schema.TextField" name="TextField">
      <analyzer>
        <tokenizer class="solr.StandardTokenizerFactory"/>
        <filter class="solr.LowerCaseFilterFactory"/>
      </analyzer>
    </fieldType>
    <fieldType class="org.apache.solr.schema.TrieDateField" name="TrieDateField"/>
    <fieldType class="org.apache.solr.schema.StrField" name="StrField"/>
  </types>
  <fields>
    <field indexed="true" multiValued="false" name="body" stored="true" type="TextField"/>
    <field docValues="true" indexed="true" multiValued="false" name="real_date" stored="true" type="TrieDateField"/>
    <field indexed="true" multiValued="false" name="title" stored="true" type="TextField"/>
    <field indexed="true" multiValued="false" name="id" stored="true" type="StrField"/>
    <field indexed="true" multiValued="false" name="date" stored="true" type="TextField"/>
    <field docValues="false" indexed="false" name="_partitionKey" type="StrField"/>
  </fields>
  <uniqueKey>id</uniqueKey>
</schema>

Reload the schema to make it active:
```
RELOAD SEARCH INDEX ON wiki.solr;
```
Rebuild the search index:
```
REBUILD SEARCH INDEX ON wiki.solr;
```