Composite Grouping

Doradus Spider supports a special grouping feature called composite grouping. It is meaningful only for aggregate queries with 2 or more grouping levels. It causes the metric function(s) to be computed for parent (non-leaf) groups in addition to leaf-most groups. The extra computations are returned as composite results within the corresponding parent groups.

Composite grouping is requested by using a special grouping parameter instead of the normal grouping parameter. For example, consider the following URI aggregate query:

GET /Msgs/Message/_aggregate?m=COUNT(*)&f=TRUNCATE(SendDate,DAY),Tags

Composite grouping can be requested for this 2-level query by using the &cf parameter instead of &f:

GET /Msgs/Message/_aggregate?m=COUNT(*)&cf=TRUNCATE(SendDate,DAY),Tags

A typical result for this 2-level aggregate query in XML is shown below:

<results>

<aggregate metric="COUNT(*)" group="TRUNCATE(SendDate,DAY),Tags"/>

<totalobjects>6032</totalobjects>

<summary>6032</summary>

<groups>

<group>

<summary>4753</summary>

<field name="SendDate">2010-07-17 00:00:00</field>

<groups>

<group>

<metric>1</metric>

<field name="Tags">(null)</field>

</group>

<group>

<metric>4752</metric>

<field name="Tags">AfterHours</field>

</group>

<group>

<metric>1524</metric>

<field name="Tags">Customer</field>

</group>

</groups>

</group>

<group>

<summary>1279</summary>

<field name="SendDate">2010-07-18 00:00:00</field>

<groups>

<group>

<metric>1279</metric>

<field name="Tags">AfterHours</field>

</group>

<group>

<metric>701</metric>

<field name="Tags">Customer</field>

</group>

</groups>

</group>

<group composite="true">

<field name="SendDate">*</field>

<groups>

<group>

<metric>1</metric>

<field name="Tags">(null)</field>

</group>

<group>

<metric>6031</metric>

<field name="Tags">AfterHours</field>

</group>

<group>

<metric>2225</metric>

<field name="Tags">Customer</field>

</group>

</groups>

</group>

</groups>

</results>

The same response in JSON is shown below:

{"results": {

"aggregate": {"metric": "COUNT(*)", "group": "TRUNCATE(SendDate,DAY),Tags"},

"totalobjects": "6032",

"summary": "6032",

"groups": [

{"group": {

"summary": "4753",

"field": {"SendDate": "2010-07-17 00:00:00"},

"groups": [

{"group": {

"metric": "1",

"field": {"Tags": "(null)"}

}},

{"group": {

"metric": "4752",

"field": {"Tags": "AfterHours"}

}},

{"group": {

"metric": "1524",

"field": {"Tags": "Customer"}

}}

]

}},

{"group": {

"summary": "1279",

"field": {"SendDate": "2010-07-18 00:00:00"},

"groups": [

{"group": {

"metric": "1279",

"field": {"Tags": "AfterHours"}

}},

{"group": {

"metric": "701",

"field": {"Tags": "Customer"}

}}

]

}},

{"group": {

"composite": "true",

"field": {"SendDate": "*"},

"groups": [

{"group": {

"metric": "1",

"field": {"Tags": "(null)"}

}},

{"group": {

"metric": "6031",

"field": {"Tags": "AfterHours"}

}},

{"group": {

"metric": "2225",

"field": {"Tags":"Customer"}

}}

]

}}

]

}}

As shown, composite grouping produces an extra group for non-leaf grouping levels. This group is marked with a composite property of true, and the value for its field element is “*”. Within the composite group, lower-level metric groups are provided for each lower-level grouping field value, however, these lower-level metrics are computed across all objects at the composite grouping level. In the example above, the composite group computes the metric function (COUNT(*)) for all second-level groups (Tags) across all first-level group values (SendDate).

Composite grouping is only meaningful for multi-level grouping.