Re: proposal: row_to_array function

On 1/16/15 11:22 AM, Pavel Stehule wrote:
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> 2015-01-16 18:03 GMT+01:00 Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com <mailto:Jim(dot)Nasby(at)bluetreble(dot)com>>:
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> On 1/16/15 3:45 AM, Pavel Stehule wrote:
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> I am returning back to processing records in plpgsql.
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> I am thinking so it can be simply processed with transformations to array.
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> Now we have similar functions - hstore(row), row_to_json, ... but using of these functions can be a useless step. Any row variable can be transformed to 2D text array.
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> How is it useless? Why wouldn't you just use JSON and be done with it?
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> We can use a FOREACH IN ARRAY iteration in plpgsql (second variant is a implementation FOREACH for jsonb)
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> so ROW->ARRAY is shorter than ROW->JSON->ARRAY or ROW->HSTORE->ARRAY

I think the real problem here is that we're inventing a bunch of different ways to do the same thing: iterate over a set. Instead of doing that, should we add the idea of an iterator to the type system? That would make sense for arrays, hstore, json and XML.

> Do you have some use cases you can share?
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> processing of NEW, OLD variables in triggers

Note that last time I checked you couldn't do something like NEW.variable, and I don't think you could use EXEC to do it either. So there's more needed here than just converting a record to an array.

> There two possible transformations:
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> row_to_array --> [[key1, value1],[key2, value2], ...]
> row_to_row_array --> [(key1, value1), (key2, value2), ... ]
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> If we're going to go that route, I think it makes more sense to create an actual key/value type (ie: http://pgxn.org/dist/pair/doc/__pair.html <http://pgxn.org/dist/pair/doc/pair.html>) and return an array of that.
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> ok
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> --
> Jim Nasby, Data Architect, Blue Treble Consulting
> Data in Trouble? Get it in Treble! http://BlueTreble.com
>
>

--
Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com