FlatPostgresCollection createOrReplace

[suddendust]

Description

Key Changes:

1. Implements createOrReplace for FlatPostgresCollection: This handles upserts for flat postgres collections. The SQL is generated as:

INSERT INTO table (col1, col2, pk_col) VALUES (?, ?, ?) ON CONFLICT (pk_col) DO UPDATE SET col1 = EXCLUDED.col1, col2 = EXCLUDED.col2 RETURNING (xmax = 0) AS is_insert

If there's a conflict on the PK column, it basically references values from the "excluded" row (EXCLUDED is a special table that references the row that would have been inserted had there been no conflict).

RETURNING (xmax = 0) AS is_insert basically returns a 0 is it was an insert, or a 1 if it was an update. This helps us to differentiate b/w inserts and updates, which is also what the createAndReturn API returns.

2. Handles primary keys properly: The system now queries the schema registry for the PK column. If it's unable to find it, it fallbacks to they key column that is hardcoded.

3. Adds a MissingColumnStrategy.defaultStrategy() that is SKIP currently.

[codecov]

Codecov Report

❌ Patch coverage is 82.35294% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.37%. Comparing base (c855b61) to head (4cba90d).

Files with missing lines	Patch %	Lines
...documentstore/postgres/FlatPostgresCollection.java	74.28%	15 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #268      +/-   ##
============================================
- Coverage     80.70%   80.37%   -0.33%     
- Complexity     1394     1397       +3     
============================================
  Files           239      239              
  Lines          6529     6604      +75     
  Branches        601      606       +5     
============================================
+ Hits           5269     5308      +39     
- Misses          868      893      +25     
- Partials        392      403      +11     

Flag	Coverage Δ
integration	80.37% <82.35%> (-0.33%)	⬇️
unit	55.46% <27.45%> (-0.47%)	⬇️

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[puneet-traceable]

just a clarification, will this cause connection close each time we are done running these statements?

[suddendust]

Yes, it's AutoCloseable. Is that a concern?

[puneet-traceable]

so connection closed after every query/transaction? We barely utilize persistent connections?

[suddendust]

This is just a test case, we use a pooled connection in prod: https://github.com/hypertrace/document-store/pull/268/changes#diff-cb9cc13ae5f1676784171b330150156520fddb54ead6945e5494e6b62f17da50R695