Introduce declare/fetch/deallocate #89
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* Add declare(!)/3,4
* Add fetch(!)/3,4
* Add deallocate(!)/3,4
Explicitly defining handle_first/4 and handle_next/4 is deprecated
because callback implementations that are required to differentiate also
need to track cursors in their state. A single fetch/4 is cleaner to use
and these callbacks forward to handle_fetch/4 on `use DBConnection`.
For first/next/fetch the return value is `{:cont | :halt, result, state}`
where `:cont` is continue (same as :ok`) and `:halt` means both that the
cursor has finished enumerating results and the cursor is deallocated.
Therefore `:halt` does not require a `deallocate` call. This API is
chosen to avoid an extra roundtrip that current adapters do.
handle_first/4 and handle_next/4 still support `:ok` and `:deallocate`
tuples.
A callback implementation may need to deallocate if the transaction ends
without a cursor being deallocated (via `fetch/4` or `deallocate/4`).
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Explicitly defining handle_first/4 and handle_next/4 is deprecated
because callback implementations that are required to differentiate also
need to track cursors in their state. A single fetch/4 is cleaner to use
and these callbacks forward to handle_fetch/4 on
use DBConnection.For first/next/fetch the return value is
{:cont | :halt, result, state}where
:contis continue (same as :ok) and:haltmeans both that the cursor has finished enumerating results and the cursor is deallocated. Therefore:haltdoes not require adeallocatecall. This API is chosen to avoid an extra roundtrip that current adapters do. handle_first/4 and handle_next/4 still support:okand:deallocate`tuples.
A callback implementation may need to deallocate if the transaction ends
without a cursor being deallocated (via
fetch/4ordeallocate/4).