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n-young / trustdb

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Implement statement evaluation #1

Closed desmondcheongzx closed 3 years ago

desmondcheongzx commented 3 years ago

Finishing up our discussion from this afternoon, this is an implementation of statement evaluation via hashsets of records.

desmondcheongzx commented 3 years ago

One issue with a hashset implementation is that results are returned out of order. For example, say a client fed in this data:

{"Write": {"name": "disk", "labels": {"hostname": "host_desmond"}, "variables": {"total": 1099511627776.0}, "timestamp": "2016-01-01 00:04:00+00:00"}}
{"Write": {"name": "disk", "labels": {"hostname": "host_desmond"}, "variables": {"total": 2}, "timestamp": "2016-01-01 00:05:00+00:00"}}
{"Write": {"name": "disk", "labels": {"hostname": "host_desmond"}, "variables": {"total": 4}, "timestamp": "2016-01-01 00:06:00+00:00"}}

And then makes the following query:

{"Select": {"name": "test", "predicate":{"name": "test","condition":{"Leaf":{"lhs": {"LabelKey": "hostname"},"rhs": {"LabelValue": "host_desmond"},"op": "Eq"}}}}}

The following are some results returned by the server:

Received statement: Select { name: "test", predicate: Predicate { name: "test", condition: Leaf(Condition { lhs: LabelKey("hostname"), rhs: LabelValue("host_desmond"), op: Eq }) } }
Received result: [Record { name: "disk", labels: {"hostname": "host_desmond"}, variables: {"total": 1099511627776.0}, timestamp: 2016-01-01T00:04:00Z }, Record { name: "disk", labels: {"hostname": "host_desmond"}, variables: {"total": 4.0}, timestamp: 2016-01-01T00:06:00Z }, Record { name: "disk", labels: {"hostname": "host_desmond"}, variables: {"total": 2.0}, timestamp: 2016-01-01T00:05:00Z }]
Received statement: Select { name: "test", predicate: Predicate { name: "test", condition: Leaf(Condition { lhs: LabelKey("hostname"), rhs: LabelValue("host_desmond"), op: Eq }) } }
Received result: [Record { name: "disk", labels: {"hostname": "host_desmond"}, variables: {"total": 2.0}, timestamp: 2016-01-01T00:05:00Z }, Record { name: "disk", labels: {"hostname": "host_desmond"}, variables: {"total": 4.0}, timestamp: 2016-01-01T00:06:00Z }, Record { name: "disk", labels: {"hostname": "host_desmond"}, variables: {"total": 1099511627776.0}, timestamp: 2016-01-01T00:04:00Z }]
Received statement: Select { name: "test", predicate: Predicate { name: "test", condition: Leaf(Condition { lhs: LabelKey("hostname"), rhs: LabelValue("host_desmond"), op: Eq }) } }
Received result: [Record { name: "disk", labels: {"hostname": "host_desmond"}, variables: {"total": 4.0}, timestamp: 2016-01-01T00:06:00Z }, Record { name: "disk", labels: {"hostname": "host_desmond"}, variables: {"total": 2.0}, timestamp: 2016-01-01T00:05:00Z }, Record { name: "disk", labels: {"hostname": "host_desmond"}, variables: {"total": 1099511627776.0}, timestamp: 2016-01-01T00:04:00Z }]
...

The first result returns entries 1, 3, then 2. The second result returns entries 2, 3, then 1. The third result returns entries 3, 2, then 1. etc.