The mysql
extension allows DuckDB to directly read and write data from/to a running MySQL instance. The data can be queried directly from the underlying MySQL database. Data can be loaded from MySQL tables into DuckDB tables, or vice versa.
Installing and Loading
To install the mysql
extension, run:
INSTALL mysql;
The extension is loaded automatically upon first use. If you prefer to load it manually, run:
LOAD mysql;
Reading Data from MySQL
To make a MySQL database accessible to DuckDB use the ATTACH
command:
ATTACH 'host=localhost user=root port=0 database=mysql' AS mysqldb (TYPE mysql)
USE mysqldb;
The connection string determines the parameters for how to connect to MySQL as a set of key=value
pairs. Any options not provided are replaced by their default values, as per the table below.
Setting | Default |
---|---|
host | localhost |
user | current user |
password | |
database | NULL |
port | 0 |
socket | NULL |
The tables in the file can be read as if they were normal DuckDB tables, but the underlying data is read directly from MySQL at query time.
SHOW TABLES;
┌───────────────────────────────────────┐
│ name │
│ varchar │
├───────────────────────────────────────┤
│ signed_integers │
└───────────────────────────────────────┘
SELECT * FROM signed_integers;
┌──────┬────────┬──────────┬─────────────┬──────────────────────┐
│ t │ s │ m │ i │ b │
│ int8 │ int16 │ int32 │ int32 │ int64 │
├──────┼────────┼──────────┼─────────────┼──────────────────────┤
│ -128 │ -32768 │ -8388608 │ -2147483648 │ -9223372036854775808 │
│ 127 │ 32767 │ 8388607 │ 2147483647 │ 9223372036854775807 │
│ NULL │ NULL │ NULL │ NULL │ NULL │
└──────┴────────┴──────────┴─────────────┴──────────────────────┘
It might be desirable to create a copy of the MySQL databases in DuckDB to prevent the system from re-reading the tables from MySQL continuously, particularly for large tables.
Data can be copied over from MySQL to DuckDB using standard SQL, for example:
CREATE TABLE duckdb_table AS FROM mysqlscanner.mysql_table;
Writing Data to MySQL
In addition to reading data from MySQL, create tables, ingest data into MySQL and make other modifications to a MySQL database using standard SQL queries.
This allows you to use DuckDB to, for example, export data that is stored in a MySQL database to Parquet, or read data from a Parquet file into MySQL.
Below is a brief example of how to create a new table in MySQL and load data into it.
ATTACH 'host=localhost user=root port=0 database=mysqlscanner' AS mysql_db (TYPE mysql_scanner);
CREATE TABLE mysql_db.tbl(id INTEGER, name VARCHAR);
INSERT INTO mysql_db.tbl VALUES (42, 'DuckDB');
Many operations on MySQL tables are supported. All these operations directly modify the MySQL database, and the result of subsequent operations can then be read using MySQL.
Note that if modifications are not desired, ATTACH
can be run with the READ_ONLY
property which prevents making modifications to the underlying database. For example:
ATTACH 'host=localhost user=root port=0 database=mysqlscanner' AS mysql_db (TYPE mysql_scanner, READ_ONLY);
Below is a list of supported operations.
CREATE TABLE
CREATE TABLE mysql_db.tbl(id INTEGER, name VARCHAR);
INSERT INTO
INSERT INTO mysql_db.tbl VALUES (42, 'DuckDB');
SELECT
SELECT * FROM mysql_db.tbl;
┌───────┬─────────┐
│ id │ name │
│ int64 │ varchar │
├───────┼─────────┤
│ 42 │ DuckDB │
└───────┴─────────┘
COPY
COPY mysql_db.tbl TO 'data.parquet';
COPY mysql_db.tbl FROM 'data.parquet';
UPDATE
UPDATE mysql_db.tbl SET name='Woohoo' WHERE id=42;
DELETE
DELETE FROM mysql_db.tbl WHERE id=42;
ALTER TABLE
ALTER TABLE mysql_db.tbl ADD COLUMN k INTEGER;
DROP TABLE
DROP TABLE mysql_db.tbl;
CREATE VIEW
CREATE VIEW mysql_db.v1 AS SELECT 42;
CREATE SCHEMA/DROP SCHEMA
CREATE SCHEMA mysql_db.s1;
CREATE TABLE mysql_db.s1.integers(i int);
INSERT INTO mysql_db.s1.integers VALUES (42);
SELECT * FROM mysql_db.s1.integers;
┌───────┐
│ i │
│ int32 │
├───────┤
│ 42 │
└───────┘
DROP SCHEMA mysql_db.s1;
Transactions
CREATE TABLE mysql_db.tmp(i INTEGER);
BEGIN;
INSERT INTO mysql_db.tmp VALUES (42);
SELECT * FROM mysql_db.tmp;
┌───────┐
│ i │
│ int64 │
├───────┤
│ 42 │
└───────┘
```sql
ROLLBACK;
SELECT * FROM mysql_db.tmp;
┌────────┐
│ i │
│ int64 │
├────────┤
│ 0 rows │
└────────┘
Note that DDL statements are not transactional in MySQL.
Settings
name | description | default |
---|---|---|
mysql_experimental_filter_pushdown | Whether or not to use filter pushdown (currently experimental) | false |
mysql_tinyint1_as_boolean | Whether or not to convert TINYINT(1) columns to BOOLEAN | true |
mysql_debug_show_queries | DEBUG SETTING: print all queries sent to MySQL to stdout | false |
mysql_bit1_as_boolean | Whether or not to convert BIT(1) columns to BOOLEAN | true |
Schema Cache
To avoid having to continuously fetch schema data from MySQL, DuckDB keeps schema information - such as the names of tables, their columns, etc - cached. If changes are made to the schema through a different connection to the MySQL instance, such as new columns being added to a table, the cached schema information might be outdated. In this case, the function mysql_clear_cache
can be executed to clear the internal caches.
CALL mysql_clear_cache();