Error map
ActiveRecord::IrreversibleMigration Rails: ActiveRecord::IrreversibleMigration — This migration uses remove_column without a type; db:rollback can't reverse it
Ruby / Rails · layer 4, Application & API
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Directly related (12)
Rails: ActiveRecord::PendingMigrationError — Migrations are pending. To resolve this issue, run: bin/rails db:migrate
The database schema is behind the migration files in the app.
MySQL ERROR 1146 (42S02): Table 'db.table' doesn't exist
The query references a table that MySQL can’t find in that database.
MySQL ERROR 1060 (42S21): Duplicate column name 'x'
A CREATE/ALTER adds a column that already exists, or a SELECT in a view/derived table produces two columns with the same name.
MySQL ERROR 1051 (42S02): Unknown table 'x'
DROP TABLE targeted a table that doesn’t exist.
MySQL ERROR 1061 (42000): Duplicate key name 'x'
CREATE INDEX/ADD INDEX used an index name that already exists on the table.
PostgreSQL: ERROR: relation "x" does not exist
The table/view isn’t found — missing migration, wrong schema, or a case-sensitive quoted name.
ERROR: relation "x" already exists
CREATE TABLE/INDEX/SEQUENCE used a name that already exists in that schema.
ERROR: cannot drop table x because other objects depend on it
Views, foreign keys or other objects depend on what you’re dropping.
MySQL ERROR 1091 (42000): Can't DROP 'x'; check that column/key exists
ALTER TABLE tried to drop a column or index that doesn’t exist.
ERROR: column "x" of relation "y" already exists
ALTER TABLE ADD COLUMN for a column that’s already there.
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.
Browser: Access to fetch at 'http://localhost:3000/api/items' from origin 'http://localhost:5173' has been blocked by CORS policy — Rails
The browser blocks calls from your front end to the Rails API because CORS headers are missing.
Two steps away (34)
Laravel: SQLSTATE[42S02]: Base table or view not found: 1146 Table 'db.sessions' doesn't exist
Laravel queried a table that hasn’t been created — usually sessions, cache, jobs or a new model’s table.
django.db.utils.OperationalError: no such table: app_model
Django queried a table that hasn’t been created — migrations missing or not applied.
sqlite3.OperationalError: no such column: x
SQLite can’t find the column — missing migration, typo, or a string written in double quotes.
MySQL ERROR 1044 (42000): Access denied for user to database
The login succeeded, but the user has no privileges on the database you’re using.
MySQL ERROR 1064 (42000): You have an error in your SQL syntax
MySQL couldn’t parse the query. The text after “near” shows where parsing failed.
MySQL ERROR 1054 (42S22): Unknown column in 'field list'
The query references a column that doesn’t exist in the table (or an unquoted string being read as a column).
MySQL ERROR 1007 (HY000): Can't create database 'x'; database exists
CREATE DATABASE ran for a database that already exists.
MySQL ERROR 1008 (HY000): Can't drop database 'x'; database doesn't exist
DROP DATABASE targeted a database that isn’t there.
MySQL ERROR 1067 (42000): Invalid default value for 'created_at'
A column’s DEFAULT isn’t allowed in the current SQL mode — classically '0000-00-00 00:00:00' with NO_ZERO_DATE.
MySQL ERROR 1005 (HY000): Can't create table (errno: 150 "Foreign key constraint is incorrectly formed")
A foreign key definition is invalid — the referenced column’s type, index or charset doesn’t match.
MySQL ERROR 1075 (42000): Incorrect table definition; there can be only one auto column and it must be defined as a key
An AUTO_INCREMENT column isn’t indexed (or there are two auto-increment columns).
MySQL ERROR 1215 (HY000): Cannot add foreign key constraint
The foreign key can’t be created — mismatched column types, missing index, or incompatible engines/collations.
MySQL ERROR 1071 (42000): Specified key was too long; max key length is 767 bytes
An index on a VARCHAR is too long for the row format — classic with utf8mb4 VARCHAR(255) on MySQL 5.6/MariaDB 10.1.
Room cannot verify the data integrity. Looks like you've changed schema but forgot to update the version number
The Room entity definitions changed, but the database version wasn’t increased or no migration was provided.
dotnet ef: Unable to create a 'DbContext' of type ''. The exception 'Unable to resolve service for type DbContextOptions' was thrown while attempting to create an instance
dotnet ef migrations couldn’t construct your DbContext at design time.
PostgreSQL: FATAL: password authentication failed for user
PostgreSQL rejected the password for that role, or pg_hba.conf requires a different auth method.
PostgreSQL: ERROR: column "x" does not exist
PostgreSQL can’t find the column — a missing migration, a case-sensitive quoted name, or a string literal written in double quote…
SQL Server: Invalid object name 'x'. (Msg 208)
The table/view doesn’t exist in the current database or schema.
API Error: Request failed schema validation (must NOT have additional properties / Additional properties are not allowed)
The JSON body doesn’t match the endpoint’s schema — an unknown property, wrong nesting, or a missing required object.
MongoDB: MongoServerError: Document failed validation (code 121)
The collection has a JSON Schema validator and the inserted/updated document doesn’t satisfy it.
Rails: ActiveRecord::StatementInvalid: PG::DuplicateColumn: ERROR: column "status" of relation "orders" already exists
A migration tried to add a column/table/index that already exists.
ERROR: prepared statement "s1" already exists (PgBouncer transaction mode)
Named prepared statements collided — typically because PgBouncer in transaction pooling mode hands connections between clients.
pg_dump: error: aborting because of server version mismatch
Your pg_dump client is older than the server you’re dumping.
pg_restore: error: input file appears to be a text format dump. Please use psql.
A plain .sql dump was given to pg_restore, which only reads custom/directory/tar formats.
Laravel: SQLSTATE[42S01]: Base table or view already exists: 1050 Table 'users' already exists
A migration tries to create a table that is already in the database.
Laravel: SQLSTATE[42000]: Syntax error or access violation: 1071 Specified key was too long; max key length is 767 bytes
An indexed string column exceeds the index size allowed by an older MySQL/MariaDB with utf8mb4.
Laravel migration: SQLSTATE[HY000]: General error: 1005 Can't create table (errno: 150 "Foreign key constraint is incorrectly formed")
MySQL can't create the foreign key because column types, order or engines don't match the referenced table.
ERROR: database "x" is being accessed by other users — There is 1 other session using the database.
DROP/RENAME DATABASE can’t run while other sessions are connected.
MySQL ERROR 1062 (23000): Duplicate entry for key
An INSERT/UPDATE would create a duplicate value in a PRIMARY or UNIQUE key.
MySQL ERROR 1452: Cannot add or update a child row: a foreign key constraint fails
You inserted/updated a row whose foreign key value doesn’t exist in the referenced parent table.
org.hibernate.exception.ConstraintViolationException: could not execute statement
The database rejected an insert/update because of a constraint (unique, foreign key, not null).
Browser: Access to XMLHttpRequest at 'https://api.example.com' from origin 'http://localhost:3000' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header — Laravel
The browser blocked a cross-origin call to your Laravel API because the response lacks the right CORS headers.
Browser: Access to fetch at 'https://api.example.com/api/data' from origin 'https://app.example.com' has been blocked by CORS policy (Next.js route handler)
A cross-origin request to your Next.js API route is blocked because the response lacks CORS headers.
Rails: ActiveRecord::ConnectionNotEstablished: No connection pool for 'ActiveRecord::Base' found
ActiveRecord has no database connection configured or established for this process.
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