dbdiff
Compares two databases and prints SQL commands to modify the first one in order to match the second one.
It does NOT execute the statements. It only prints the statements.
It supports PostgreSQL and MySQL.
Installing
Install globally with npm
npm install dbdiff -g
CLI Usage
dbdiff \
-l safe
dialect://user:pass@host[:port]/dbname1 \
dialect://user:pass@host[:port]/dbname2
Where dialect can be either postgres or mysql. The first database url denotes the target, the second the source, the sql queries will allow target to be updated to source state.
The flag -l or --level indicates the safety of the SQL. Allowed values are safe, warn and drop
Safety level
Some statements may fail or may produce data loss depending on the data stored in the target database.
- When the
safelevel is specified, only SQL statements that are guaranteed to preserve existing data will be printed. Any other command will be commented out. - When the
warnlevel is specified also SQL statements that may fail because of existing data will be printed. These commands are for example: changes in data types or dropping aNOT NULLconstraint. - When the
droplevel is specified all SQL statements are printed and this may containDROP COLUMNorDROP TABLEstatements.
Dropping a sequence or dropping an index is considered safe.
Changing the data type of existing columns
Sometimes Postgresql won't be able to change the existing data to the new data type. In that case you will get an error similar to this:
ERROR: column "column_name" cannot be cast automatically to type integer
HINT: Specify a USING expression to perform the conversion.
You can manually specify a USING expression to perform de conversion. For example to convert text to integers:
ALTER TABLE table_name
ALTER column_name TYPE data_type USING column_name::integer
Usage as a library
You can use dbdiff as a library:
var dbdiff = require('dbdiff')
dbdiff.describeDatabase(connString)
.then((schema) => {
// schema is a JSON-serializable object representing the database structure
})
var diff = new dbdiff.DbDiff()
// Compare two databases passing the connection strings
diff.compare(conn1, conn2)
.then(() => {
console.log(diff.commands('drop'))
})
// Compare two schemas
diff.compareSchemas(schema1, schema2)
console.log(diff.commands('drop'))You can pass connection strings such as postgres://user:pass@host:5432/dbname1 or objects to these methods. For example:
dbdiff.describeDatabase({
dialect: 'postgres', // use `mysql` for mysql
username: 'user',
password: 'pass',
database: 'dbname1',
host: 'localhost',
dialectOptions: {
ssl: false
}
})
.then((schema) => {
// ...
})Example of .describeDatabase() output
{
"tables": [
{
"name": "users",
"schema": "public",
"indexes": [],
"constraints": [
{
"name": "email_unique",
"schema": "public",
"type": "unique",
"columns": [
"email"
]
},
{
"name": "users_pk",
"schema": "public",
"type": "primary",
"columns": [
"id"
]
}
],
"columns": [
{
"name": "id",
"nullable": false,
"default_value": "nextval('users_id_seq'::regclass)",
"type": "integer"
},
{
"name": "email",
"nullable": true,
"default_value": null,
"type": "character varying(255)"
}
]
},
{
"name": "items",
"schema": "public",
"indexes": [],
"constraints": [
{
"name": "items_fk",
"schema": "public",
"type": "foreign",
"columns": [
"user_id"
],
"referenced_table": "users",
"referenced_columns": [
"id"
]
}
],
"columns": [
{
"name": "id",
"nullable": false,
"default_value": "nextval('items_id_seq'::regclass)",
"type": "integer"
},
{
"name": "name",
"nullable": true,
"default_value": null,
"type": "character varying(255)"
},
{
"name": "user_id",
"nullable": true,
"default_value": null,
"type": "bigint"
}
]
}
],
"sequences": [
{
"data_type": "bigint",
"numeric_precision": 64,
"numeric_precision_radix": 2,
"numeric_scale": 0,
"start_value": "1",
"minimum_value": "1",
"maximum_value": "9223372036854775807",
"increment": "1",
"schema": "public",
"name": "users_id_seq",
"cycle": false
},
{
"data_type": "bigint",
"numeric_precision": 64,
"numeric_precision_radix": 2,
"numeric_scale": 0,
"start_value": "1",
"minimum_value": "1",
"maximum_value": "9223372036854775807",
"increment": "1",
"schema": "public",
"name": "items_id_seq",
"cycle": false
}
]
}