PostgreSQL throws duplicate_table (SQLSTATE 42P07) when a CREATE statement tries to create a table that already exists in the target schema.
PostgreSQL Error 42P07 duplicate_table appears when a CREATE TABLE collides with an existing relation. Verify the table with \dt, then either drop/rename it or rewrite the command as CREATE TABLE IF NOT EXISTS to resolve the conflict.
PostgreSQL Error 42P07 - duplicate_table
PostgreSQL raises the duplicate_table error when a CREATE TABLE, CREATE MATERIALIZED VIEW, or similar statement tries to define a relation that already exists in the current schema. The server stops execution and returns SQLSTATE 42P07.
This schema conflict blocks deployments, migrations, and ad-hoc scripts.
Understanding why the relation already exists and how to handle it prevents downtime and broken CI pipelines.
The most common trigger is rerunning a migration that contains an unconditional CREATE TABLE command. Because the table was created during a prior run, the second run collides with the existing relation.
Another frequent cause is case-sensitive naming confusion.
PostgreSQL stores unquoted identifiers in lowercase; attempting to create "MyTable" after "mytable" already exists yields a duplicate.
Automated tools that generate temporary tables inside loops may fail to clean up, leaving behind a leftover relation that collides on the next run.
First confirm the table truly exists with \dt in psql or by querying pg_catalog.pg_class.
If the existing table is the desired one, skip creation or use CREATE TABLE IF NOT EXISTS.
If the old table is obsolete, drop or rename it, then rerun the migration.
For case discrepancies, quote identifiers consistently or stick to lowercase names.
When running migrations in Galaxy, enable "Idempotent mode" so the editor automatically wraps CREATE statements with IF NOT EXISTS, preventing duplicate_table interruptions.
Repeated CI migrations - Add IF NOT EXISTS or guard the script with a check against information_schema.tables.
Branch merges containing identical table definitions - Use PgBouncer safe migrations or a schema-comparison step before applying changes.
Temp table collisions in analytics notebooks - Append a session-unique suffix or use ON COMMIT DROP temporary tables.
Write idempotent DDL using CREATE TABLE IF NOT EXISTS and DROP TABLE IF EXISTS.
This makes scripts safe to rerun.
Adopt a migration framework (e.g., Flyway, Liquibase) that tracks applied versions to prevent duplicate execution.
Use lowercase, snake_case identifiers to avoid accidental case collisions. Galaxy’s linter flags mismatched casing before the query runs.
42710 duplicate_object – Similar conflict but for indexes, constraints, and other objects.
Use IF NOT EXISTS syntax or DROP first.
42P01 undefined_table – Raised when referencing a table that does not exist; check schema search_path or spelling.
55006 object_in_use – Cannot drop table because other sessions are using it; terminate blocking sessions or wait.
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Yes. Add IF NOT EXISTS to CREATE statements so PostgreSQL skips creation without raising an error.
Yes, if a temp table name is reused in the same session without DROP or ON COMMIT DROP, the error is triggered.
Using separate schemas avoids name collisions, but you must set search_path properly to reference the correct table.
Galaxy’s SQL copilot suggests IF NOT EXISTS automatically and flags duplicate identifiers before the script runs.
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