Add UUID type conversion and fix datetime comparison

[theelderbeever]

Reference Issue #404

Motivation

The querystring builder is valuable when trying to write custom complex queries with VALUES however, certain values are not converted to sql compatible values properly. This results in Table.raw(query).run() failing. Changes here aspire to address this issue.

Explanation

A couple of type check fixes. The datetime comparison in the querystring was comparing to the module not the class and wouldn't be picked up. Additionally, the .replace("T", " ") doesn't work with postgres as far as I can tell and I removed it.

There also needs to be a check on UUID. When being written to a query string the value should be wrapped in ''.

I imagine something similar may need to be done with JSONB, Enum, etc. Maybe there could be some merging of usage with the piccolo.utils.sql_values.convert_to_sql_value function.

[dantownsend]

Ideally it would check both of these, because for Postgres, a value could be a uuid.UUID or asyncpg.pgproto.pgproto.UUID.

We pass uuid.UUID into queries like INSERT, but asyncpg returns asyncpg.pgproto.pgproto.UUID from SELECT. We're most likely to be dealing with uuid.UUID.

[theelderbeever]

asyncpg only gets installed if the piccolo[postgres] is installed, correct? I am not sure I have a good idea on how the case where it hasn't been installed other than moving the find_spec("asyncpg") into the conversion if-elif-else scope (l# 103). Is that what you would recommend?

[theelderbeever]

or something like

if find_spec("asyncpg"):
    from asyncpg.pgproto.pgproto import UUID as apgUUID
else:
    from uuid import UUID
    apgUUID = UUID

Then do the appropriate typecheck with an or on line 102

[dantownsend]

Yes, that works.

[dantownsend]

@theelderbeever Thanks for this. The changes are definitely useful.

The string representation of a query is more of a convenience, so you can do something like print(Band.select()) and immediately see the SQL that would be generated. That's why there might be bugs with it, because Piccolo doesn't use it directly in queries.

I think this issue has also made it clear that an API is needed for composing custom queries with Querystring, like await Manager.run_querystring(querystring). I'll create a separate issue for that.

[codecov-commenter]

Codecov Report

Merging #405 (6b298e5) into master (1e384dd) will decrease coverage by 0.00%.
The diff coverage is 77.77%.

@@            Coverage Diff             @@
##           master     #405      +/-   ##
==========================================
- Coverage   90.84%   90.83%   -0.01%     
==========================================
  Files         103      103              
  Lines        6826     6833       +7     
==========================================
+ Hits         6201     6207       +6     
- Misses        625      626       +1     

Impacted Files	Coverage Δ
piccolo/querystring.py	89.87% <77.77%> (-0.41%)	⬇️

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[dantownsend]

@theelderbeever Thanks, looks good 👍