[Fix] Searching test results with execution metadata never returns

[rpbritton]

Description

Searching test results with execution metadata never returns. It takes too long.

My fix here is a refactor. I believe the previous solution was building a VERY large table in memory. This implementation is more in line with standard practices and performs quite a bit better with a large number of test executions and test results.

Resolved issues

Cannot use metadata on test results page.

Documentation

N/A

Web service API changes

N/A

Tests

Purely a refactor, all unit tests for attachment rules and test results search that depend on this logic still pass.

Tested locally using a restored dump of the production test observer database. Verified without the change that the page will not load, and with the change it does.

[Copilot]

Pull Request Overview

This PR fixes a performance issue where searching test results with execution metadata never returns due to inefficient query construction. The fix refactors the filter_execution_metadata function to use a more efficient approach with EXISTS subqueries instead of building large in-memory tables.

• Replaces complex values table and outer joins with simpler EXISTS subqueries for each metadata category
• Removes unnecessary imports (func, values, column) and adds explicit join requirement
• Improves query performance by avoiding large table construction in memory

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