Get entity by attribute

[jhrozek]

Summary

Adds a utility database function to search entities by ID. Because we
store entity properties as JSON, we add a GIN index.

Testing with 50.000 entities we get the following performance:

Nested Loop  (cost=30.39..109.45 rows=5 width=87) (actual time=0.290..0.292 rows=1 loops=1)
  ->  Bitmap Heap Scan on properties p  (cost=30.10..67.90 rows=5 width=16) (actual time=0.216..0.218 rows=1 loops=1)
"        Recheck Cond: (value @> '{""value"": ""MBymWMNbcv"", ""version"": ""v1""}'::jsonb)"
        Filter: (key = 'upstream_id'::text)
        Heap Blocks: exact=1
        ->  Bitmap Index Scan on idx_properties_value_gin  (cost=0.00..30.10 rows=10 width=0) (actual time=0.174..0.175 rows=1 loops=1)
"              Index Cond: (value @> '{""value"": ""MBymWMNbcv"", ""version"": ""v1""}'::jsonb)"
  ->  Index Scan using entity_instances_pkey on entity_instances ei  (cost=0.29..8.31 rows=1 width=87) (actual time=0.069..0.069 rows=1 loops=1)
        Index Cond: (id = p.entity_id)
        Filter: (entity_type = 'repository'::entities)
Planning Time: 2.365 ms
Execution Time: 0.590 ms

Compared to not using the index:

Nested Loop  (cost=0.29..3165.63 rows=5 width=87) (actual time=0.117..42.194 rows=1 loops=1)
  ->  Seq Scan on properties p  (cost=0.00..3124.07 rows=5 width=16) (actual time=0.032..42.108 rows=1 loops=1)
"        Filter: ((value @> '{""value"": ""MBymWMNbcv"", ""version"": ""v1""}'::jsonb) AND (key = 'upstream_id'::text))"
        Rows Removed by Filter: 100004
  ->  Index Scan using entity_instances_pkey on entity_instances ei  (cost=0.29..8.31 rows=1 width=87) (actual time=0.082..0.082 rows=1 loops=1)
        Index Cond: (id = p.entity_id)
        Filter: (entity_type = 'repository'::entities)
Planning Time: 1.104 ms
Execution Time: 42.300 ms

Related: #4179

• Bug fix (resolves an issue without affecting existing features)
• Feature (adds new functionality without breaking changes)
• Breaking change (may impact existing functionalities or require documentation updates)
• Documentation (updates or additions to documentation)
• Refactoring or test improvements (no bug fixes or new functionality)

Testing

make test + as part of a larger branch

Review Checklist:

• Reviewed my own code for quality and clarity.
• Added comments to complex or tricky code sections.
• Updated any affected documentation.
• Included tests that validate the fix or feature.
• Checked that related changes are merged.

[coveralls]

coverage: 53.951% (+0.004%) from 53.947%
when pulling 1b69cd4 on jhrozek:prop_search_by_attr
into 8f63f4b on stacklok:main.