poc: allow extracting individual steps (#2065)

[ulfryk]

@jatcwang a promised PoC so we can make some decisions early on :)

[jatcwang]

I'm not sure these methods are really needed? Especially since the current API does not really allow users to work with (execute) a PreparedExecutionStream directly

[jatcwang]

I agree with the overall direction you're going with this. I think it will provide most if not all of the customizations users will need 👍

[ulfryk]

@jatcwang

Methods added to Query class:

• toAlteringExecution (as to)
• toMapAlteringExecution (as toMap)
• accumulateAlteringExecution (as accumulate)
• uniqueAlteringExecution (as unique)
• optionAlteringExecution (as option)
• nelAlteringExecution (as nel)

Methods added to Update class:

• runAlteringExecution (as run)
• updateManyAlteringExecution (as updateMany)
• withUniqueGeneratedKeysAlteringExecution (as withUniqueGeneratedKeys)

So basically all operations returning ConnectionIO.
As suggested in #2154 (comment) I have skipped ones yielding Stream.

---

Now some questions:

• should we use this name pattern - …AlteringExecution suffix?
• should we add similar methods to the Query0 and Update0 traits?

[jatcwang]

Thanks this looks good! Sorry for the late reply.

I think AlteringExection is good! One other possibility I can think of is Customized e.g. toMapCustomized.

Yes we'll need to add these to Query0 and Update0 too