Add support for QuestDB's LIMIT clause in SQLAlchemy dialect

[jerrinot]

Implements QuestDB's LIMIT clause in SQLAlchemy dialect. Key features:

• Standard LIMIT N syntax
• LIMIT lower,upper range syntax (lower exclusive, upper inclusive)
• Support for expressions and bind parameters
• Automatic conversion of SQLAlchemy's LIMIT/OFFSET

Example:

select(table).limit(5)               # LIMIT 5
select(table).limit(3).offset(2)     # LIMIT 2,5
select(table).offset(8)              # LIMIT 8,BIGINT_MAX

This addressed the 2nd bullet from #25

[raycardillo]

Anything I can to do help move this one along? I have a use-case where I need the OFFSET to work with Superset and I just noticed this PR. I might try to experiment with it myself and confirm it resolves that problem, but there is a very real need for translating OFFSET to LIMIT for QuestDB. In the case of Superset, they use it for more efficient server side pagination, and they use it for pagination with their "drill down" mode when exploring data behind a chart, etc.

[raycardillo]

Just to confirm, I installed this branch into my venv for my Superset installation, and it worked like a charm!! Now I am looking forward to see it merged. It has enabled server side pagination and drill down for me. :D

[cardilloscreations]

@nwoolmer Is there anything I could do to help here? Not sure I have the bandwidth, but without a solution for OFFSET/LIMIT in the SQLAlchemy connector for QuestDB, we cannot make use of server side pagination and other features where Superset requires support for the LIMIT clause. See issue #29 for details.

[nwoolmer]

I'll raise it!

[nwoolmer]

@cardilloscreations Sorry for the delay on this one, aiming for a release Monday :)

[cardilloscreations]

@nwoolmer Awesome! Thanks! :D

[jerrinot]

@cardilloscreations: just FYI - the newly released 1.1.4 contains this fix.