ext/pdo_pgsql: Expanding COPY input from an array to an iterable

[KentarouTakeda]

This pull request allows PDO::pgsqlCopyFromArray to accept Iterable instead of just array. This is not a breaking change since it still accepts array.

The PostgreSQL COPY statement is a great interface. We can bulk insert a set of records by inputting them as CSV or TSV. PostgreSQL also supports processing them as a stream.

However, the current pgsqlCopyFromArray does not take full advantage of this capability. It requires that the records to be inserted be input as a single array, so it cannot be processed by piping external input to PostgreSQL's COPY.

This weakness will be overcome by supporting not only simple arrays but also Traversable and Generator.

[devnexen]

Nice feature and qualifies for the next major release I think. looking ok overall, I would suggest trying to refactor, as much as you can, common code between the two modes.

[KentarouTakeda]

I'll try it.

[KentarouTakeda]

I tried to do as much as I could.
(Actually, I'm not very familiar with the C language. Please feel free to let me know if I'm doing something strange.)

[devnexen]

Couple of things to look at I think, good news is because of this

qualifies for the next major release I think

you have the time.

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