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21 lines
846 B
ReStructuredText
21 lines
846 B
ReStructuredText
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CapnProto
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---------
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Cap'n Proto is a binary message format. Like Protocol Buffers and Thrift (but unlike JSON or MessagePack), Cap'n Proto messages are strongly-typed and not self-describing. Due to this, it requires a ``schema`` setting to specify schema file and the root object. The schema is parsed on runtime and cached for each SQL statement.
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.. code-block:: sql
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SELECT SearchPhrase, count() AS c FROM test.hits GROUP BY SearchPhrase FORMAT CapnProto SETTINGS schema = 'schema.capnp:Message'
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When the schema file looks like:
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.. code-block:: text
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struct Message {
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SearchPhrase @0 :Text;
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c @1 :Uint64;
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}
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Deserialisation is almost as efficient as the binary rows format, with typically zero allocation overhead per message.
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You can use this format as an efficient exchange message format in your data processing pipeline.
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