feat(redshift) support approx count distinct

[pauldheinrichs]

Check List

• Tests has been run in packages where changes made if available
• Linter has been run for changed code
• Tests for the changes have been added if not covered yet
• Docs have been added / updated if required

Add support for redshift approx distinct calls (i think) please feel free to make changes or whatever to help get this through. I would just like to start using this for additive measures in cube and would love this to get in sooner rather than later 😅

Docs: https://docs.aws.amazon.com/redshift/latest/dg/hyperloglog-functions.html

Issue Reference this PR resolves
Fixes: #8510

Description of Changes Made (if issue reference is not provided)

[Description goes here]

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[igorlukanin]

If this gets through @paveltiunov's review, I think changes to this docs section would be needed: https://cube.dev/docs/product/configuration/data-sources/aws-redshift#count_distinct_approx

[pauldheinrichs]

Tested with pre-aggregation:

• Successfully created pre-aggregation SQL

 - Executing Load Pre Aggregation SQL: scheduler-ba104a65-512d-4700-aaeb-67caa9743162
--
  CREATE TABLE dev_pre_aggregations.session_funnel_main20240101_ubycvf3l_wiz2w3y_1jafait AS SELECT
      "session_funnel".step "session_funnel__step", date_trunc('day', ("session_funnel".t::timestamptz AT TIME ZONE 'UTC')) "session_funnel__time_day", count("session_funnel".user_id) "session_funnel__conversions", CASE WHEN HLL("session_funnel".first_step_user_id) > 0 THEN 100.0 * count("session_funnel".user_id) / HLL("session_funnel".first_step_user_id) ELSE NULL END "session_funnel__conversions_percent", HLL("session_funnel".first_step_user_id) "session_funnel__first_step_conversions"
    FROM

[pauldheinrichs]

Validated non pre-aggregated queries,

SELECT
      date_trunc('day', ("session_funnel".t::timestamptz AT TIME ZONE 'UTC')) "session_funnel__time_day", CASE WHEN APPROXIMATE COUNT(DISTINCT "session_funnel".first_step_user_id) > 0 THEN 100.0 * count("session_funnel".user_id) / APPROXIMATE COUNT(DISTINCT "session_funnel".first_step_user_id) ELSE NULL END "session_funnel__conversions_percent"
    FROM
      (
      ```

[paveltiunov]

@pauldheinrichs Thanks for contributing! I guess hllInit should use https://docs.aws.amazon.com/redshift/latest/dg/r_HLL_CREATE_SKETCH.html

[pauldheinrichs]

@pauldheinrichs Thanks for contributing! I guess hllInit should use https://docs.aws.amazon.com/redshift/latest/dg/r_HLL_CREATE_SKETCH.html

@paveltiunov I attempted that in this 71e0882 commit actually and resulting not super succesfully when testing? Unless i tested wrong? 🤔

[paveltiunov]

@pauldheinrichs Hard to tell what's went wrong but according to the doc HLL already does an estimation and it isn't something we want to happen in hllInit.

[paveltiunov]

@pauldheinrichs It feels we need HLL_CARDINALITY(HLL_COMBINE(${sql})) for hllMerge and also HLL_COMBINE(${sql}) for hllMergeOnly. But this one needs to be tested.

[igorlukanin]

@pauldheinrichs Given that AWS HLL format spec is proprietary and HLL support can't be also brought to Cube Store, I wonder how useful this addition to the Redshift driver is. WDYT?