Database Migration Planner

1. Before/after schema

PostgreSQL 16 subset only. Paste CREATE TABLE and CREATE INDEX definitions; each statement needs a semicolon. All identifiers are simple unquoted names.

Review-only planner. It does not inspect live data, outside objects, migrations already applied, table locks or backups. Never run generated SQL without database review.

Examples

Before DDLOpen Before DDL file

After DDLOpen After DDL file

Table renames (one per line)Column renames (one per line)

Use old_table -> new_table or old_table.old_column -> new_column. Column mappings use the old table name, even if that table is renamed.

I reviewed the unpaired old/new names and intend separate add/drop operations, not a rename.

Supported syntax and limits

CREATE TABLE t (id integer NOT NULL, name text, PRIMARY KEY (id), CONSTRAINT fk FOREIGN KEY (id) REFERENCES parent (id)); CREATE [UNIQUE] INDEX idx ON t (name); Types: integer, bigint, text, boolean, date, uuid, timestamp [with time zone], varchar(n), numeric(p[,s]). A referenced column needs a modeled single-column primary or unique key.

No quoted/schema-qualified names, defaults, serial/identity, CHECK, UNIQUE table constraints, composite foreign keys, ON DELETE actions, ALTER statements, views, triggers, partial/expression/concurrent indexes or arbitrary SQL. Unsupported input is rejected entirely.

At most 24,000 DDL characters per snapshot, 32 tables, 256 columns, 64 indexes and 64 foreign keys. This is a schema model, not a dump loader.

Comments & questions

Compare two small PostgreSQL 16 schema snapshots instead of comparing SQL characters. A strict, local parser models tables, columns, one-column named foreign keys, primary keys and simple indexes. It orders dependency removal, renames, additions and final constraints. Unpaired old/new names are ambiguous until you map them as a rename or explicitly confirm replacement. Destructive and validation-sensitive steps require individual review; unsupported changes block SQL export. This planner never connects to a database or knows its rows, views, permissions or deployment locks.

Key features

Strict PostgreSQL 16 DDL subset and whole-input errors instead of silent partial parsing
Explicit table and column renames; unpaired names stay ambiguous
Ordered table, column, index and foreign-key changes with dependency notes
High-risk acknowledgment and manual blockers before SQL export
Local JSON review report and gated PostgreSQL SQL download

How to use

Paste the previous and desired CREATE TABLE/INDEX snapshots or open local SQL files.
Use an example and map each intended rename with old -> new; treat unpaired names as intentional only after review.
Analyze and inspect ordered objects, dependencies, high-risk drops and manual blockers.
Acknowledge each high-risk step to unlock review SQL; check it against a backup and real database before using it.

Use cases

Plan an explicit column rename without silently deleting its values
Check that an old foreign key is removed before a referenced table is dropped
See a unique index or new foreign key as a data-dependent validation risk
Flag a type change or new required column for manual backfill planning

Frequently asked questions

Which SQL dialect and statements work?

Only a bounded PostgreSQL 16 subset: unquoted lowercase-style identifiers, CREATE TABLE with supported primitive column types and optional NOT NULL, table-level PRIMARY KEY, named single-column FOREIGN KEY, and simple CREATE [UNIQUE] INDEX. Other syntax fails closed.

Does the planner infer a rename?

No. A removed name and a new name might be a rename or two separate operations. Supply an explicit table/column mapping; otherwise confirm intentional replacement before SQL export. Individual destructive steps also need acknowledgment.

Will the SQL safely migrate production data?

No automatic execution occurs. The script has BEGIN/COMMIT and RESTRICT, but live rows, outside views/functions, locks, permissions, backfills and rollback plans are unknown. Test with a backup and review with a database operator.

Why is type change or a new NOT NULL column blocked?

PostgreSQL may require a USING expression or a backfill and may reject existing rows. This tool does not invent data conversions or defaults.

Do existing foreign keys and indexes affect ordering?

Modeled obsolete foreign keys and indexes are removed first; new tables are created without foreign keys, and new constraints are added last. Unmodeled external dependencies can still block RESTRICT.

Privacy

DDL and rename text are parsed in this browser only. The tool does not connect to a database or submit schemas to an application API; downloads are local.

References

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