qa-db-migrations

Adversarial performance reviewer for a single database migration (Flyway V*.sql, Liquibase changeset, Atlas migration). Flags missing CONCURRENTLY on index creation, full-table-rewrite ALTERs holding ACCESS EXCLUSIVE locks, missing post-migration statistics (ANALYZE), partition-pruning hazards, and lock-time estimates for large-table operations. Emits a BLOCK / PASS verdict with a findings table. Use before merging any migration PR to catch slow-path DDL that the correctness-focused migration-blast-radius-reviewer does not cover; that agent covers breaking changes, rollback paths, and consumer coordination - this agent covers only DDL locking and query-performance impact.

Adversarial reviewer for a single database migration (Flyway V*.sql, Liquibase changeset, Atlas migration, or SQLMesh model change). Classifies operations as additive / breaking / data-loss / locking / lock-escalating; estimates downtime risk for large-table operations; identifies downstream consumers via grep on column/table names; flags missing rollback path; surfaces unsafe defaults (NOT NULL add without default, narrow column type change, foreign-key add without index). Returns Critical / Warning / Info findings table. Use proactively before merging any DB migration PR.

Authors and runs Atlas database schema migrations - declarative HCL or SQL schema definition with `atlas schema apply` for desired-state apply OR `atlas migrate diff` to generate versioned migrations against a dev DB; `atlas migrate apply` to deploy; `atlas migrate lint` to flag destructive / locking / data-loss patterns; `atlas migrate hash` to detect tampering. Supports PostgreSQL, MySQL, SQL Server, ClickHouse, SQLite, MariaDB, Snowflake, Oracle, Redshift, Spanner, CockroachDB, Databricks. Use when the user wants Terraform-style declarative DB schema management or modern SQL-first migration linting beyond Flyway / Liquibase.

Authors and runs Flyway database migrations - versioned (`V1__add_users.sql`), repeatable (`R__refresh_views.sql`), and undo (`U1__remove_users.sql`) migration files in `db/migration/`; runs `flyway migrate` / `info` / `validate` / `clean` / `baseline` / `repair`; tracks state in the `flyway_schema_history` table; supports 50+ databases including Oracle / SQL Server / MySQL / PostgreSQL / MariaDB / Snowflake / BigQuery; integrates with Maven, Gradle, CLI, and Docker. Use when the user works with Flyway-managed schemas, asks about migration ordering, or needs CI gates on schema changes.

Authors and runs Liquibase database migrations - changelog-driven schema management with changesets in XML / YAML / JSON / SQL formats; supports `liquibase update` / `status` / `rollback` / `tag` / `history` lifecycle; offers per-changeset preconditions, contexts and labels for selective execution, and rollback semantics; tracks state in `DATABASECHANGELOG` + `DATABASECHANGELOGLOCK` tables. Use when the user works with Liquibase-managed schemas (Spring Boot heritage, polyglot DB shops), needs cross-DBMS portable migrations, or requires fine-grained rollback control.

Authors and runs SQLMesh - data-transformation framework with version control, virtual data environments, automatic breaking-vs-non-breaking change classification, and downstream impact analysis; supports `sqlmesh init` / `plan` / `apply` / `run` / `audit` / `test` lifecycle; covers DuckDB, Postgres, Snowflake, BigQuery, Redshift, Databricks. Use when the user works with SQL data pipelines (warehouse + dbt-adjacent ELT), needs safer model evolution than dbt's deploy-and-pray, or wants the strongest impact-analysis story in the OSS data tooling space.