Add Record en-/decoder

[larskanis]

Original report by Lars Kanis (Bitbucket: larskanis, GitHub: larskanis).

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Original post: https://groups.google.com/forum/#!topic/ruby-pg/ikdlp67c5RA

The current implementation of decoders and encoders doesn't support embedded Records of composite type?

What I'd like to do is decode the following example:

CREATE TYPE example AS (a string, b integer, c boolean);
CREATE TABLE test (id integer, sample example);
INSERT INTO test VALUES (1, '("Some text",123,false)');
SELECT * FROM test;

The query returns the following values, before decoder:

result['id'] === 1
result['sample'] === '("Some text",123,false)'

What I'd like to do is something like the "PG::TextDecoder::Array#decode" method, but with a mix of decoder functions, returning:

result['sample'] === ['Some text', 123, false]

[larskanis]

Original comment by Lars Kanis (Bitbucket: larskanis, GitHub: larskanis).

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I started the implementation of a record en-/ decoder, but it's around 30% yet.

[larskanis]

Original comment by Lars Kanis (Bitbucket: larskanis, GitHub: larskanis).

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The postgres implementation is in rowtypes.c. We need a new Coder type next to PG::SimpleCoder, PG::CopyCoder and PG::CompositeCoder. I would call it PG::RowCoder. I haven't got it further so far - still around 30%.

[larskanis]

Original comment by Carlos Ferreira da Silva (Bitbucket: crash-tech, GitHub: crash-tech).

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Is this still a feature to come? I built this gem PostgreSQL that relies deeply on these advanced features from PostgreSQL, and requires correct decoding and encoding of the data. I've created this override Torque::PostgreSQL::Coder which is basically an extension of the current available Decoder/Encoder. Let me know if I can help with this, the change seems to be pretty simple and maybe I can open a PR for that.

[larskanis]

Original comment by Lars Kanis (Bitbucket: larskanis, GitHub: larskanis).

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I implemented the required encoder and decoder in C: ged/ruby-pg#36

[larskanis]

Original comment by Lars Kanis (Bitbucket: larskanis, GitHub: larskanis).

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Add PG::RowCoder for en/decoding of Composite Types

This implements proper encoder and decoder for Composite Types
as described in https://www.postgresql.org/docs/11/rowtypes.html
and as requested in https://bitbucket.org/ged/ruby-pg/issues/258

This adds the following classes:

• PG::RowCoder < PG::Coder
• PG::RowEncoder < PG::RowCoder
• PG::RowDecoder < PG::RowCoder
• PG::TextEncoder::Row < PG::RowEncoder
• PG::TextDecoder::Row < PG::RowDecoder

Fixes #258