Update check for table existence to be case insensitive

[dlstadther]

Description

Redshift schema/table/column names are case-insensitive. So if you create table MyTable in schema MySchema, redshift saves those values in pg_table_def and information_schema.tables in all lowercase. Therefore, the check for table existence in does_table_exist() will fail.

This PR just surrounds the table and schema parameters in lower().

From Redshift documentation:

ASCII letters in standard and delimited identifiers are case-insensitive and are folded to lower case.

Motivation and Context

Resolves Issue #2080

Have you tested this? If so, how?

Works for me.

[mention-bot]

@dlstadther, thanks for your PR! By analyzing the history of the files in this pull request, we identified @ddaniels888, @rantav and @steenzout to be potential reviewers.

[dlstadther]

@Tarrasch All tests passed except the two which haven't been running for anyone.

[Tarrasch]

Cool, also feel free self-merge these changes to an area where you have expertise.

[dlstadther]

@Tarrasch I would have, but my write access to this repo was removed.

Thanks for merging!