Fix applying changeset to DB with constraints on Postgres#235
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wonder-sk merged 6 commits intoMerginMaps:masterfrom Dec 18, 2025
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Fix applying changeset to DB with constraints on Postgres#235wonder-sk merged 6 commits intoMerginMaps:masterfrom
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Previously some code would leak the PGresult, wrapping it with our PostgresResult right away means the destructor will take care of that.
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This PR is a follow-up to #232, which fixed this issue (#210) for SQLite only. This Postgres version follows roughly the same formula, where we first try to apply all changeset entries, then select those which failed due to constraint conflicts and then try to apply them in a loop until they all apply or we get stuck.
Postgres can defer constraints, but those constraints have to be made deferrable in the first place. This has performance implications (per the documentation), but also deferrable constraints can't be made targets of FOREIGN KEY constraints, so our hacky looping is still sadly necessary.
By default any error rolls back the whole transaction. Since we need statement-level feedback, we have to create a new SAVEPOINT around each statement.