Xata

Xata branches and pre-merge impact analysis

Xata is a Postgres-at-scale platform. Branches are copy-on-write copies of a Postgres database. Each branch is a standard Postgres endpoint with its own connection string. Treat a Xata branch as a normal postgres connection.

Connect to a workspace

Register a Xata workspace as a xata-type connection, not as a raw postgres URL. The stored secret is a scoped Xata API key, not a database connection string. The gateway resolves the per-branch Postgres endpoint server-side. Set the workspace, region, database, and default branch on the connection.

Do not paste a postgresql://...xata.sh/... URL as a connection. Store the API key on a xata connection and let the gateway build the endpoint. One workspace connection addresses every branch.

Diff two branches

Call xata_branch_diff(connection_name, base_branch, compare_branch) to compare two branches from one workspace connection. The gateway swaps the branch on the stored credential and diffs the two live schemas. Use this for the pre-merge gate.

Call schema_diff_branches(base_connection, compare_connection) when the two branches are registered as two separate connections instead.

Do not use schema_diff to compare branches. schema_diff compares one connection against its own cached snapshot, not against another connection.

List branches

Call xata_list_branches(connection_name, project) to list the branches in a Xata project. Each branch shows its name, id, and parent branch.

Pre-merge impact workflow

Run this before a feature branch merges into the base branch.

1. Diff the branches with schema_diff_branches(base, feature).
2. For each removed column, find every dbt model whose SQL selects that column from the changed source table. Each such model is a breaking change.
3. For each removed column, find every dbt test (accepted_values, not_null, unique, relationships) on that column. Each such test is a breaking change.
4. For each type change, flag models that use the column as a warning. Flag any accepted_values test on that column as breaking when the new type is numeric and the listed values are strings.
5. Propagate downstream: any model that ref()s a breaking model is a warning, because it cannot build once its parent fails.
6. Report a verdict. Any breaking change means do not merge.

The static report is a superset of what a dbt run surfaces. A dbt run stops at the first failed node in a chain and skips the rest. The static report lists every break, not just the first one dbt hits.

pgroll migrations

Xata applies schema changes with pgroll (xata roll). pgroll runs expand then contract. During expand it keeps the old and new columns both live, exposed through versioned view schemas named public_<migration_name>. Applications select a version with SET search_path = 'public_<migration_name>'.

When a branch under review uses pgroll expand/contract, the old column still exists until pgroll complete runs. Recommend the expand/contract path as the safe remediation: it lets the warehouse migrate to the new column before the old one is dropped, so the merge does not break the pipeline.

Introspect only the application schema (for example raw) when diffing. Ignore pgroll's internal pgroll schema and its <schema>_<migration> version schemas.