[*] repurpose duplicate_count in DROP INDEX recommendations

[avandras]

Description

The current query has a usecase-specific column, which semantically doesn't feel right (the usecase is a value like 'duplicate' or 'invalid' whereas the column name is duplicate_count. Also, with the proposed change a query which has looked like

WITH q_invalid AS (
  SELECT count(*) as cnt
    FROM recommendations
   WHERE time = (SELECT max(time) 
                   FROM recommendations 
                  WHERE $__timeFilter(time)
                    AND dbname = '$dbname' 
                    AND tag_data->>'reco_topic' = 'drop_index' 
                    AND tag_data->>'issue_type' = 'invalid'
                )
  AND dbname = '$dbname' AND tag_data->>'reco_topic' = 'drop_index' AND tag_data->>'issue_type' = 'invalid'
)
SELECT sum((data->>'duplicate_count')::int8) + (select cnt from q_invalid)::int8
  FROM recommendations
 WHERE time = (
               select max(time)
                 from recommendations
                where $__timeFilter(time)
                  AND dbname = '$dbname' 
                  AND tag_data->>'reco_topic' = 'drop_index' 
                  AND tag_data->>'issue_type' = 'duplicate'
              )
  AND dbname = '$dbname' AND tag_data->>'reco_topic' = 'drop_index' AND tag_data->>'issue_type' = 'duplicate'

would turn into the arguably easier to understand

WITH collection_time AS (
    SELECT max(time) AS max_time
      FROM recommendations 
     WHERE $__timeFilter(time)
       AND dbname = '$dbname' 
       AND tag_data->>'reco_topic' = 'drop_index'
)
SELECT sum((data->>'affected_count')
  FROM recommendations 
  JOIN collection_time ON time = max_time
 WHERE dbname = '$dbname' 
   AND tag_data->>'reco_topic' = 'drop_index'
   AND tag_data->>'issue_type' IN ('duplicate', 'invalid')

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• I am the human author and take full personal responsibility for every change in this PR.
• No AI or automated generative tool was used in any part of this PR OR I have disclosed all tool(s) below.

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Checklist

• Code compiles and existing tests pass locally.
• New or updated tests are included where applicable.
• Documentation is updated where applicable.

[coveralls]

Coverage Report for CI Build 27702759741

Coverage increased (+0.1%) to 85.966%

Details

• Coverage increased (+0.1%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	5451
Covered Lines:	4686
Line Coverage:	85.97%
Coverage Strength:	0.98 hits per line

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💛 - Coveralls