Use SHOW_COLUMNS to fetch Snowflake's schema

[arikfr]

Issue Summary

The current method of refreshing the Snowflake schema is starting a cluster, which is undesired -- specially when doing a background refresh of the schema.

We can alternatively use SHOW_COLUMNS to load the schema without waking a up a cluster.

Technical details:

• Redash Version: v8

[monicagangwar]

@arikfr are there any tests for snowflake with which any change to snowflake query runner can be verified ?

[arikfr]

@monicagangwar this is a great question. Sadly, the answer is no :-( Most of the query runners are untested. It's something we do want to address (see #3807), but will take us time to get there.

[monicagangwar]

@arikfr alright. Although i've seen there is no pagination handled while refreshing schema.
A/c to the documentation for SHOW COLUMNS

The command returns a maximum of 10K records for the specified object type, as dictated by the access privileges for the role used to execute the command; any records above the 10K limit are not returned, even with a filter applied.

Should I handle this in the PR ?

[arikfr]

@monicagangwar let's ignore the 10K limit for now. If we get reports of this being an issue will try to think of how to address it.

Thanks!

[bradleyhurley]

@arikfr - Can this issue be closed? I was looking for some low hanging fruit I could help out with, but it seems the update was already merged.

[arikfr]

@bradleyhurley definitely. Thanks for noticing!