Make keyset cursor pagination NULL-aware#1331
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Cursor.SQLFragment emitted a seek predicate with no NULL handling, so once a page boundary landed on a NULL order value the WHERE matched no rows and pagination terminated early, silently dropping the remaining rows. Rewrite SQLFragment to render the predicate from a template that emits explicit NULLS placement and a null-aware, type-agnostic seek, mirroring the direction and NULLS placement on the Head/Tail inversion so backward paging stays an exact inverse. For NOT NULL columns it reduces to the previous predicate. Cover the whole cursor stack with tests: a real-Postgres pagination walk (e2e/page) that drives the production SQLFragment/SQLArguments forward and backward through every NULL edge case, plus unit tests for the generated SQL and arguments, cursor-key serialization, page trimming, and order direction parsing. Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>
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Cursor.SQLFragment emitted a seek predicate with no NULL handling, so once a page boundary landed on a NULL order value the WHERE matched no rows and pagination terminated early, silently dropping the remaining rows.
Rewrite SQLFragment to emit explicit NULLS placement and a null-aware, type-agnostic seek predicate, mirroring the direction and NULLS placement on the Head/Tail inversion so backward paging stays an exact inverse. For NOT NULL columns it reduces to the previous predicate.
Add white-box pagination tests that evaluate the generated SQL with three-valued logic and walk the whole set forward and backward across the NULL boundary.
Summary by cubic
Makes keyset cursor pagination NULL-aware so pages don’t truncate when the sort column has NULLs. Adds explicit NULLS placement and a null-aware seek; backward paging mirrors forward exactly.
Tests
+785-0@cursor_field_valueappears only for non-NULL seeks.CursorKeyround-trip and invalid formats,OrderDirectiontext marshaling, andPagetrimming/HasNext/HasPrev for Head/Tail.Service
+67-21Cursor.SQLFragmentvia a template that sets ASC/DESC, NULLS FIRST/LAST, and id tiebreak; Tail flips both for symmetry.@cursor_field_valueonly when non-NULL.Other
+2-2./e2e/page/....Written for commit 00d4d5f. Summary will update on new commits.