Add support for partial indexes

[alcaeus]

MongoDB 3.2 adds support for partial indexes. This PR adds support for adding partialIndexExpression options to the index specification.

Examples:

• YAML:

  indexes:
    index1:
      keys:
        username: desc
      options:
        unique: true
        dropDups: false
        partialFilterExpression:
          version: { $gt: 1 }
          discr: { $eq: 'default' }

• XML:

<indexes>
    <index unique="true">
        <key name="username" order="desc" />
        <option name="dropDups" value="false" />
        <partialFilterExpression>
            <field name="version" value="1" operator="gt" />
            <field name="discr" operator="eq" value="default" />
        </partialFilterExpression>
    </index>
</indexes>

• Annotations:

/**
 * @ODM\Indexes(
 *     @ODM\Index(keys={"username"="asc"},dropDups=true,partialFilterExpression={"counter"={"$gt"=5}})
 * )
 */

List of TODOs:

• Figure out how to properly map $and in XML
• Ensure SchemaManager::isMongoIndexEquivalentToDocumentIndex() works properly
• You can always add more tests

[alcaeus]

Long time no see, I've updated the XML mapping. The example in the comment above outlines the straight-forward mapping. For more complicated mappings, there are additional possiblilities. You can either check properties of embedded documents (checking only those properties mentioned):

<partialFilterExpression>
    <field name="nested">
        <field name="count" operator="gt" value="0" />
        <field name="test" value="foo" />
    </field>
</partialFilterExpression>

Or check a document for equality (ensuring that a document looks exactly like what's provided):

<partialFilterExpression>
    <field name="object" operator="eq">
        <field name="property" value="foo" />
        <field name="count" value="bleh" />
    </field>
</partialFilterExpression>

With this it's also possible to use the $and operator. MongoDB supports this operator only at the root level:

<partialFilterExpression>
    <and>
        <field name="nested">
            <field name="count" operator="gt" value="0" />
            <field name="test" value="foo" />
        </field>
    </and>
    <and>
        <field name="object" operator="eq">
            <field name="property" value="foo" />
            <field name="count" value="bleh" />
        </field>
    </and>
</partialFilterExpression>

When using and, you cannot add any field mappings at the root level. You also can't nest the and operator in a field mapping.

[malarzm]

Missing space before ! ;)

[malarzm]

I think we should have tests for expression with and since XML driver has a check on that?

[alcaeus]

@malarzm Good idea, I'll add a few extra documents to be safe.

[alcaeus]

@malarzm Added tests for various filter expressions being loaded via XML and YAML to ensure they are the same. Invalid filter expressions will only be fixed by the XML driver as YAML and annotations are schemaless and will just let the database throw a fit if the expression is invalid.

[malarzm]

👍