Error map
SQLAlchemy OperationalError sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) connection to server … failed
Python · layer 4, Application & API
Centre: this error. First ring: errors it is linked with (8). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (8)
PostgreSQL: could not connect to server / connection refused — Is the server running on host and accepting TCP/IP connections?
The client reached no PostgreSQL listener at that host/port — the server is down, listening elsewhere, or not accepting remote co…
org.hibernate.LazyInitializationException: could not initialize proxy - no Session
A lazy-loaded association was accessed after the Hibernate session/transaction closed.
HikariPool-1 - Connection is not available, request timed out after 30000ms
The connection pool was exhausted — all connections were busy for 30 seconds.
MySQL ERROR 2006 (HY000): MySQL server has gone away
The connection to MySQL was closed — usually by a timeout or a packet larger than `max_allowed_packet`.
sqlalchemy.exc.IntegrityError: (psycopg2.errors.UniqueViolation) duplicate key value violates unique constraint
A database constraint (unique, foreign key, not null) rejected an insert/update made through SQLAlchemy.
org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing
An entity references another entity that hasn’t been saved yet, and no cascade is configured.
org.hibernate.exception.ConstraintViolationException: could not execute statement
The database rejected an insert/update because of a constraint (unique, foreign key, not null).
SequelizeConnectionRefusedError: connect ECONNREFUSED 127.0.0.1:5432
Sequelize couldn’t connect to the database server.
Two steps away (21)
MySQL ERROR 2002 (HY000): Can't connect to local MySQL server through socket
The client couldn’t reach the MySQL server — it isn’t running, or the client is looking for the socket/port in the wrong place.
PostgreSQL: FATAL: password authentication failed for user
PostgreSQL rejected the password for that role, or pg_hba.conf requires a different auth method.
Error: connect ECONNREFUSED 127.0.0.1:5432
Nothing is listening at that host:port — the target service is down or you’re connecting to the wrong address.
com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class X and no properties discovered
Jackson can’t serialize the class — it has no public getters/fields, or it’s a Hibernate proxy, or Java 8 date types without the…
IncorrectResultSizeDataAccessException: query did not return a unique result: 2
A query expected one row but found several.
Performance: N+1 query problem (one query per row in a loop)
Code runs one query to load a list, then one more query per item — hundreds of queries per page.
Lock wait timeout exceeded; try restarting transaction (MySQL 1205)
A query waited too long for a row lock held by another transaction and gave up.
MySQL ERROR 1040 (08004): Too many connections
MySQL reached `max_connections` and refuses new clients.
com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
The MySQL JDBC driver couldn’t reach the database (or the connection dropped).
MySQL ERROR 1045 (28000): Access denied for user
MySQL rejected the login — wrong password, wrong user/host combination, or the user doesn’t exist.
Deadlock found when trying to get lock; try restarting transaction
Two transactions waited on each other’s locks; the database killed one so the other could continue.
MySQL ERROR 1049 (42000): Unknown database 'x'
The database named in the connection doesn’t exist on that server.
MySQL ERROR 1062 (23000): Duplicate entry for key
An INSERT/UPDATE would create a duplicate value in a PRIMARY or UNIQUE key.
PostgreSQL: ERROR: duplicate key value violates unique constraint
An INSERT/UPDATE would create a duplicate in a UNIQUE or PRIMARY KEY column — or the id sequence is behind the existing data.
API Error: Resource already exists (ALREADY_EXISTS / resource_already_exists / 409)
The create request was refused because an object with the same unique identity — name, email, external ID — already exists.
MySQL ERROR 1022 (23000): Can't write; duplicate key in table
An ALTER/CREATE produced a duplicate key or constraint name — often a foreign key name that already exists in the database.
PrismaClientKnownRequestError P2002: Unique constraint failed on the fields: (`email`)
A Prisma create/update violated a unique constraint.
ERROR: update or delete on table "users" violates foreign key constraint on table "orders" — Key (id)=(5) is still referenced
You tried to delete a row that other rows still reference.
MongooseError: Operation `users.find()` buffering timed out after 10000ms
Mongoose queued a query waiting for a connection that never opened.
MongooseServerSelectionError: connect ECONNREFUSED 127.0.0.1:27017
The MongoDB driver couldn’t find a reachable server for the connection string.
Error: P1001: Can't reach database server at `host`:`5432`
Prisma couldn’t connect to the database in DATABASE_URL.
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