Correctly treat top level JSONB null value

[tsg]

Description

We have an issue where if a jsonb column is null, not the usual Postgres NULL, but as json null (DEFAULT 'null'::jsonb in postgres speak), the following was happening:

• Go pgx deserialized it as a regular nil
• When inserting it was transformed in a postgres NULL
• if the column has a NOT NULL constraint, the insert fails.

Checked and this was an issue for snapshot only. The wal2json code path doesn't have this issue.

Type of Change

Please select the relevant option(s):

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🔧 Refactoring (no functional changes)
• ⚡ Performance improvement
• 🧪 Test coverage improvement
• 🔨 Build/CI changes
• 🧹 Code cleanup

Changes Made

Testing

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed
• All existing tests pass

Checklist

• Code follows project style guidelines
• Self-review completed
• Code is well-commented
• Documentation updated where necessary

Additional Notes

[github-actions]

Merging this branch changes the coverage (3 decrease, 1 increase)

Impacted Packages	Coverage Δ	🤖
github.com/xataio/pgstream/internal/postgres	30.52% (-0.85%)	👎
github.com/xataio/pgstream/pkg/snapshot/generator/postgres/data	77.14% (-0.96%)	👎
github.com/xataio/pgstream/pkg/stream	40.19% (+0.30%)	👍
github.com/xataio/pgstream/pkg/stream/integration	0.00% (ø)
github.com/xataio/pgstream/pkg/wal/processor/postgres	78.17% (-0.23%)	👎

---

Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
github.com/xataio/pgstream/internal/postgres/pg_conn_pool.go	0.00% (ø)	48 (+8)	0	48 (+8)
github.com/xataio/pgstream/internal/postgres/pg_utils.go	46.72% (-2.90%)	137 (+8)	64	73 (+8)	👎
github.com/xataio/pgstream/pkg/snapshot/generator/postgres/data/config.go	0.00% (ø)	17	0	17
github.com/xataio/pgstream/pkg/snapshot/generator/postgres/data/pg_snapshot_generator.go	83.25% (-1.21%)	209 (+3)	174	35 (+3)	👎
github.com/xataio/pgstream/pkg/stream/config.go	84.80% (+0.63%)	125 (+5)	106 (+5)	19	👍
github.com/xataio/pgstream/pkg/stream/stream_run.go	0.00% (ø)	89 (+1)	0	89 (+1)
github.com/xataio/pgstream/pkg/stream/stream_snapshot.go	0.00% (ø)	28 (+1)	0	28 (+1)

Please note that the "Total", "Covered", and "Missed" counts above refer to code statements instead of lines of code. The value in brackets refers to the test coverage of that file in the old version of the code.

Changed unit test files

• github.com/xataio/pgstream/internal/postgres/pg_utils_integration_test.go
• github.com/xataio/pgstream/pkg/stream/config_test.go
• github.com/xataio/pgstream/pkg/stream/integration/snapshot_pg_integration_test.go
• github.com/xataio/pgstream/pkg/wal/processor/postgres/jsonb_serialization_test.go