Allow to find table in temporary schema for Redshift

[galachad]

Issue:

> DBI::dbWriteTable(con, "iris", iris, temporary = TRUE, overwrite = TRUE)
> DBI::dbWriteTable(con, "iris", iris, temporary = TRUE, overwrite = TRUE)
 Error: Failed to fetch row: ERROR:  Relation "iris" already exists 

Using

(SELECT 1 AS nr, current_schema() AS table_schema) ttt

is nice solution but it do not return temporary schema same as current_schemas(true).

This change works correctly with temp schema after creating temporary table in Redshift.

[krlmlr]

Thanks, this is amazing! A slew of tests now pass on Redshift, 4025336. The only thing that seems to be missing now is dbRemoveTable(temporary = TRUE) . Any idea how to achieve this?

[krlmlr]

Also, I'd appreciate a brief review of my CTE rewrite.

[galachad]

The changes look great. I also added support for dbRemoveTable(temporary = TRUE) in Redshift, please check. It's possible to return error/warning when the temp schema not exist yet but the standard behavior of function looks ok here.

[krlmlr]

Thanks a lot, this looks great! A few remarks:

• Do the schema names always start with pg_temp_ ? The pattern should be pg_temp_% in this case perhaps.
• If we can't fetch the schema name because it doesn't exist, we should raise an error if fail_if_missing is TRUE .
• Should we cache the schema name so that it is fetched only once?
• Can we extract the logic of obtaining the schema name into a function? This function can return NULL if the temp schema doesn't exist yet, or perhaps take a fail_if_missing argument.

Would you like to take another stab?

[galachad]

Sure

• Yes it's pg_temp_%, I think Redshift is managing temp schema just by adding access to one of existing schemas and clean up after finish connection. Redshift doesn't has alias like in Postgres.

SELECT * FROM pg_catalog.pg_namespace WHERE nspname like 'pg_temp_%'

• I added raising error when fail_if_missing is TRUE (for Redshift).
• That's nice idea. Added.
• Extracted to find_temp_schema function.

[krlmlr]

══ Results ══════════════════════════════════════════════════════════════════════════════════════
Duration: 385.5 s

── Skipped tests  ───────────────────────────────────────────────────────────────────────────────
• tweak: omit_blob_tests (7)

[ FAIL 0 | WARN 0 | SKIP 7 | PASS 6386 ]

With all tests enabled. Thanks a lot!

[krlmlr]

One more thing: do you agree to contribute under the MIT license? Please indicate your consent or disapproval in #312. Thanks!