MarkLogic 9 Product Documentation

Administrator's Guide — Chapter 18

Defining a Range Partition Key

The partition key describes a common element or attribute in the stored documents. The value of this element or attribute in the document determines the partition in which the document is stored. A partition key is based on a range index, collection lexicon, or field of the same name set for the database. The range index, collection lexicon, or field used by the partition key must be created before the partition key is created.

For example, assume your documents all have an update-date element with a date value. The following procedure describes how to create a partition key for the update-date element:

1. Create an element range index, named update-date, on the database of type date. The details on how to create an element range index are described in Defining Element Range Indexes.
2. In the Admin UI, open the configuration page for the database, set the assignment policy to range. Additional settings appear under the assignment policy.

   

3. Set the Lower Bound Included to true if you want to include documents with a partition key value that matches the lower bound value and exclude documents that match the upper bound value. Set the Lower Bound Included to false, if you want to exclude documents with a partition key value that matches the lower bound value and include documents that match the upper bound value. For example, if the range is 2011-01-01 (lower) to 2012-01-01 (upper) and Lower Bound Included is set to false, documents with an update-date value of 2011-01-01 will not be included in the partition, but documents with an update-date value of 2011-01-02 and 2012-01-01 will be included.
4. Note the type and scalar type of the range index, field, or collection lexicon you want to use as your partition key. In this example, we use an Element range index with a scalar type of date. Set the index and scalar types in the drop down menus to list the matching range indexes, fields, or collection lexicons set for the database.

   

5. Select the range index, field, or collection lexicon you want to use as your partition key, which is update-date in this example.

   

Creating Range Partitions

Range partitions are based on forest naming conventions. A forest's partition name prefix and the rest of the forest name are separated by a dash (-). For example, a forest named June-0001 belongs to the June partition.

It is a best practice to create a default partition (a partition without a range) before creating partitions with ranges. Doing this will allow you to load documents into the default partition before you have finished creating the other partitions. As new partitions with ranges are created, the documents will be automatically moved from the default partition to the partitions with matching ranges.

All of the forests in a database configured for tiered storage must be part of a partition.

There are two ways to create a range partition:

• Creating a Range Partition with New Forests
• Creating a Range Partition from Existing Forests

$ cat create-partition.xml
<partition xmlns="http://marklogic.com/manage">
  <partition-name>2011</partition-name>
  <upper-bound>2012-01-01</upper-bound>
  <lower-bound>2011-01-01</lower-bound>
  <forests-per-host>4</forests-per-host>
  <hosts>
    <host>MyHost1</host>
    <host>MyHost2</host>
  </hosts>
</partition>
$ curl --anyauth --user user:password -X POST \
-d @create-partition.xml -H 'Content-type: application/xml' \
http://MyHost:8002/manage/v2/databases/Documents/partitions

Creating Query Partitions

When creating a query partition, you specify the query partition name, number, and the number of forests to be created for the query partition. You can also specify that the query partition be created for multiple hosts in a cluster, in which case the specified number of forests will be created on each host.

Query partitions are based on forest naming conventions. A forest's partition name prefix and the rest of the forest name are separated by a dash (-). For example, a forest named tier1-0001 belongs to the tier1 partition. Unlike range partitions, it is not necessary for all of the forests in a database configured for tiered storage to be part of a query partition.

It is a best practice to create a default query partition (a partition without a query). Doing this will allow you to load documents into the default partition before you have finished creating the other partitions. As new partitions with queries are created, the documents will be automatically moved from the default partition to the query partitions with matching queries.

For details on how to configure the database rebalancer with the query assignment policy, see the sections Query Assignment Policy, Configuring the Rebalancer on a Database, and Configuring the Rebalancer on a Forest.

Query partitions do unfiltered searches, which means that the results are not filtered for validation. For details about unfiltered queries, see the Fast Pagination and Unfiltered Searches chapter in the Query Performance and Tuning Guide.

For example, the following creates query partition number 1, named tier1, with two forests in the Documents database on the host, MyHost1:

curl -X POST --anyauth --user admin:admin \
-H "Content-type: application/json" \
-d '{
  "partition-name": "tier1",
  "partition-number": "1",
  "forests-per-host": 2,
  "host": [ "MyHost1" ],
  "option": [ "failover=none" ]
}' \
http://MyHost1:8002/manage/v2/databases/Documents/partitions

Setting the Query Assignment Policy for the Query Partition

After creating a query partition, you can use the POST /manage/v2/databases/{id|name}/partition-queries REST resource address to assign to it a query assignment policy, as described in Query Assignment Policy.

Any indexes required for the query must be created before creating the query partition.

A query assignment policy in XML takes the form:

<partition-query-properties xmlns="http://marklogic.com/manage/partition-query/properties">
  <partition-number>1</partition-number>
  <query>
      ....cts:query.....
  </query>
</partition-query-properties>

A query assignment policy in JSON takes the form:

{
  "partition-number": "1",
  "query": {
     ....cts.query.....
  }
}

The search portion is a cts:query expression, as described in the Composing cts:query Expressions chapter in the Search Developer's Guide. There can be only one cts:query per partition.

The query requires the proper index to be configured in the database. The complexity of the query affects the performance of insert and rebalancing. Therefore slow query like wildcard matching is not recommended.

For example to direct all documents that have either the word Manager or Engineer in them to the tier1 query partition created above, you would do the following:

$ cat query1.xml
<partition-query-properties xmlns="http://marklogic.com/manage/partition-query/properties">
  <partition-number>1</partition-number>
  <query>
     <cts:or-query xmlns:cts="http://marklogic.com/cts">
       <cts:word-query>
         <cts:text xml:lang="en">Manager</cts:text>
       </cts:word-query>
       <cts:word-query>
         <cts:text xml:lang="en">Engineer</cts:text>
       </cts:word-query>
     </cts:or-query>
  </query>
</partition-query-properties>
curl -X POST  --anyauth -u admin:admin \
-H "Content-Type:application/xml" -d @query1.xml \
http://gordon-1:8002/manage/v2/databases/Schemas/partition-queries

The following query assignment policy will match documents where "LastModified" is within past year:

<partition-query-properties>
    <partition-number>1</partition-number>
    <query>
        <element-range-query operator="&gt;=">
            <element>LastModified</element>
            <value type="xs:yearMonthDuration">P1Y</value>
        </element-range-query>
    </query>
</partition-query-properties>

The same query assignment policy in JSON:

{
  "partition-number": 1,
  "query": {
    "element-range-query": {
      "operator": ">=",
      "element": "LastModified",
      "value": {
        "type": "xs:yearMonthDuration",
        "val": "P1Y"
      }
    }
  }
}

Isolating a Query Partition

By default, when a search query is given to MarkLogic, all query partitions are searched, regardless of the query assignment policy set on the partition. To avoid this overhead, you can use the tieredstorage:partition-set-exclusion-enabled function to set safe-to-exclude on the query partition so that it will not be searched if the search query does not match the query assignment policy set for that partition.

When documents are distributed in query partitions based on time and date, you may want the option to always search a particular tier (typically the tier holding the most recent documents) because it may be the case that some of the documents in that tier are about to be migrated to a different tier but have not yet been moved. So if a search only matches the query set in a lower tier, the non-matching higher tier will also be searched to locate the matching documents that have not yet moved to the lower tier.

For example, you have two query partitions that hold the documents, Seafood Daily, as shown below. The query assignment policy for each compares the date of the document with the current date and sorts the documents so that one partition contains the issues from the current year and the other archives the issues from previous years. The query partition serving as the archive is set to safe-to-exclude and the query partition containing this year's issues is not set with this option.

The current year is 2016 and a search query is given that matches the query for Archive Partition will also result in a search on Current Year Partition. However, a search query that matches the Current Year Partition will exclude the Archive Partition.

Asynchronous Operations

The partition resize and migrate, as well as the forest migrate and combine operations are processed asynchronously. This is because these operations may move a lot of data and take more time than generally considered reasonable for control to return to your script. Such asynchronous operations are tracked reusing ticket endpoints. This asynchronous process is initiated by GET /manage/v2/tickets/{tid}?view=process-status, as outlined in the following steps:

The generated ticket is returned in the form:

/manage/v2/tickets/{id}?view=process-status.

You can view the status of the operation by visiting the URL. For example if the returned ticket is:

/manage/v2/tickets/8681809991198462214?view=process-status

and your host is MyHost, you can view the status of your operation using the following URL:

http://MyHost:8002/manage/v2/tickets/8681809991198462214?view=process-status

Historical ticket information can always be accessed by viewing the ticket default view.

Privileges

The following privileges are required for the resource addresses described in this section:

• GET operations require the manage-user privilege.
• PUT, POST, and DELETE operations require the manage-admin privilege.

/manage/v2/databases/{id|name}/partitions

For examples, see:

• Viewing Partitions
• Creating Range Partitions
• Creating Query Partitions

/manage/v2/databases/{id|name}/partitions/{name}

For examples, see:

• Deleting Partitions
• Resizing Partitions
• Transferring Partitions between Databases
• Migrating Forests and Partitions

/manage/v2/databases/{id|name}/partitions/{name}/properties

For examples, see:

• Taking Forests and Partitions Online and Offline
• Setting the Updates-allowed State on Partitions

/manage/v2/databases/{id|name}/partition-queries

For examples, see:

• Setting the Query Assignment Policy for the Query Partition

/manage/v2/databases/{id|name}/partition-queries/{partition-number}

/manage/v2/databases/{id|name}/partition-queries/{partition-number}/properties

/manage/v2/forests

For examples, see:

• Migrating Forests and Partitions
• Combining Forests

/manage/v2/forests/{id|name}

For an example, see:

• Retiring Forests

/manage/v2/forests/{id|name}/properties

Viewing Partitions

You can return all of the information on a partition.

For example, to return the details of the 2011 range partition on the Documents database, do the following:

curl -X GET --anyauth --user admin:admin --header \
"Content-Type:application/xml" \
http://MyHost:8002/manage/v2/databases/Documents/partitions/2011

Migrating Forests and Partitions

Forests and partitions can be migrated from one storage device to another. For example, a range partition on an SSD has aged to the point where is it less frequently queried and can be moved to a slower, less expensive, storage device to make room for a more frequently queried range partition.

For example, the 2011 range partition on the Documents database is mounted on a local disk on the host, MyHost. To migrate the 2011 range partition to the /warm-storage data directory mounted on a shared disk on the host, OurHost, do the following:

$ cat migrate-partition.xml
<migrate xmlns="http://marklogic.com/manage">
  <hosts>
    <host>OurHost</host>
  </hosts>
  <data-directory>/warm-storage</data-directory>
  <options>
    <option>failover=none</option>
    <option>local-to-shared</option>
  </options>
</migrate>
$ curl --anyauth --user user:password -X PUT \
-d @migrate-partition.xml -H 'Content-type: application/xml' \
http://MyHost:8002/manage/v2/databases/Documents/partitions/2011

If you do not specify a data-directory, the default data directory is used.

The tiered storage migration operations allow you to migrate a forest or partition between different types of storage. The following table lists the four migration options. The migration option you select determines the sequence of steps taken by tiered storage during the migration operation.

You can use the PUT /manage/v2/forests resource address to migrate individual forests. For example, the forests 2011-0001 and 2011-0002, are mounted on a local disk on the host, MyHost. To migrate these forests to the /warm-storage data directory mounted on a shared disk on the host, OurHost, do the following:

$ cat migrate-forests.xml
<forest-migrate xmlns="http://marklogic.com/manage">
  <forests>
    <forest>2011-0001</forest>
    <forest>2011-0002</forest>
  </forests>
  <host>MyHost</host>
  <data-directory>/warm-storage</data-directory>
  <options>
    <option>local-to-shared</option>
  </options>
</forest-migrate>
$ curl --anyauth --user user:password -X PUT \
-d @migrate-forests.xml -H 'Content-type: application/xml' \
http://MyHost:8002/manage/v2/forests

If failover is configured on your forests, do a full backup of database after a forest or partition migrate operation to ensure that you can recover your data should something go wrong. You may also need to increase the timeout setting on the migrate operation, as it will take longer when failover is configured.

Resizing Partitions

You can increase or decrease the number of forests in a partition. Once the resize operation has completed, the documents in the partition forests will be rebalanced for even distribution.

For example, to resize the 2011 range partition up to five forests, do the following:

$ cat resize-partition.xml
<resize xmlns="http://marklogic.com/manage">
  <forests-per-host>5</forests-per-host>
  <hosts>
    <host>MyHost</host>
  </hosts>
</resize>
$ curl --anyauth --user user:password -X PUT \
-d @resize-partition.xml -H 'Content-type: application/xml' \
http://MyHost:8002/manage/v2/databases/Documents/partitions/2011

In addition to resizing your partition, you can migrate your partition to another host by specifying a different host in the payload. Additionally, you can move the partition to a different storage tier (such as local-to-shared) by specifying one of the migration options described in Migrating Forests and Partitions.

If you resize partitions for databases configured for database replication, first resize the replica partitions before resizing the master partitions.

Transferring Partitions between Databases

You can move a partition from one database to another. For example, to transfer the 2011 range partition from the DB1 database to the DB2 database, do the following:

$ cat transfer-partition.xml
<transfer xmlns="http://marklogic.com/manage">
  <destination-database>DB2</destination-database>
</transfer>
$ curl --anyauth --user user:password -X PUT \
-d @transfer-partition.xml -H 'Content-type: application/xml' \
http://MyHost:8002/manage/v2/databases/DB1/partitions/2011

Combining Forests

You can use the PUT /manage/v2/forests resource address to combine multiple forests into a single forest. For example, to combine the forests, 2011-0001 and 2011-0002, into a single forest, named 2011, do the following:

$ cat combine-forests.xml
<forest-combine xmlns="http://marklogic.com/manage">
  <forests>
    <forest>2011-0001</forest>
    <forest>2011-0002</forest>
  </forests>
  <forest-name>2011</forest-name>
  <hosts>
    <host>MyHost</host>
  </hosts>
</forest-combine>
$ curl --anyauth --user user:password -X PUT \
-d @combine-forests.xml -H 'Content-type: application/xml' \
http://MyHost:8002/manage/v2/forests

You can both combine forests and migrate the combined forest to another host in a single operation by specifying a different host value. You can also move the forests to a different storage tier (such as local-to-shared) by specifying one of the migration options described in Migrating Forests and Partitions.

If you want to combine forests that are attached to databases configured for database replication, first combine the foreign replica forests with the snapshot option before combining the master forests.

If failover is configured on your forests, do a full backup of database after a forest combine operation to ensure that you can recover your data should something go wrong. You may also need to increase the timeout setting on the combine operation, as it will take longer when failover is configured.

Retiring Forests

You can retire a forest from a database in order to move all of its documents to the other forests and rebalance them among those forests, as described in How Data is Moved when a Forest is Retired from the Database.

For example, to retire the forest, 2011, from the Documents database, do the following:

curl -i -X POST --digest --user user:password -H \
"Content-Type:application/x-www-form-urlencoded" \
--data "state=retire&database=Documents" \
http://MyHost:8002/manage/v2/forests/2011

Taking Forests and Partitions Online and Offline

You can take a forest or partition offline and store it in an archive, so that it is available to later bring back online, if necessary. The benefit of taking data offline is to spare the RAM, CPU, and network resources for the online data.

An offline forest or partition is excluded from query, update, backup, restore and replicate operations performed by the database to which it is attached. An offline forest or partition can be attached, detached, or deleted. Operations, such as rename, forest-level backup and restore, migrate, and combine are not supported on an offline forest or partition. If a forest is configured with failover, the replica forest inherits the online/offline setting of its master forest, so disabling an offline master forest does not trigger a failover.

For example, to take the 2011 range partition in the DB2 database offline, do the following:

$ cat partition-offline.xml
<partition-properties xmlns="http://marklogic.com/manage">
  <availability>offline</availability>
</partition-properties>

$ curl --anyauth --user user:password -X PUT \
-d @partition-offline.xml -H 'Content-type: application/xml' \
http://MyHost:8002/manage/v2/databases/DB2/partitions/2011/properties

Setting the Updates-allowed State on Partitions

You can change the updates-allowed state of a partition to make its forests. The possible states are shown in the table below.

For example, to set the updates-allowed state in the 2011 range partition in the Documents database to read-only, do the following:

$ cat read-only-partition.xml
<partition-properties xmlns="http://marklogic.com/manage">
  <updates-allowed>read-only</updates-allowed>
</partition-properties>
$ curl --anyauth --user user:password -X PUT \
-d @read-only-partition.xml -H 'Content-type: application/xml' \
http://MyHost:8002/manage/v2/databases/Documents/partitions/2011/properties

Deleting Partitions

You can delete a partition, along with all its forests. For example, to delete the 2011 range partition from the Documents database, do the following:

$ curl --anyauth --user user:password -X DELETE \
-H 'Content-type: application/xml' \
http://MyHost:8002/manage/v2/databases/Documents/partitions/2011