mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-12-15 10:52:30 +00:00
143 lines
4.8 KiB
Markdown
143 lines
4.8 KiB
Markdown
---
|
|
slug: /en/engines/database-engines/postgresql
|
|
sidebar_position: 40
|
|
sidebar_label: PostgreSQL
|
|
---
|
|
|
|
# PostgreSQL
|
|
|
|
Allows to connect to databases on a remote [PostgreSQL](https://www.postgresql.org) server. Supports read and write operations (`SELECT` and `INSERT` queries) to exchange data between ClickHouse and PostgreSQL.
|
|
|
|
Gives the real-time access to table list and table structure from remote PostgreSQL with the help of `SHOW TABLES` and `DESCRIBE TABLE` queries.
|
|
|
|
Supports table structure modifications (`ALTER TABLE ... ADD|DROP COLUMN`). If `use_table_cache` parameter (see the Engine Parameters below) it set to `1`, the table structure is cached and not checked for being modified, but can be updated with `DETACH` and `ATTACH` queries.
|
|
|
|
## Creating a Database {#creating-a-database}
|
|
|
|
``` sql
|
|
CREATE DATABASE test_database
|
|
ENGINE = PostgreSQL('host:port', 'database', 'user', 'password'[, `schema`, `use_table_cache`]);
|
|
```
|
|
|
|
**Engine Parameters**
|
|
|
|
- `host:port` — PostgreSQL server address.
|
|
- `database` — Remote database name.
|
|
- `user` — PostgreSQL user.
|
|
- `password` — User password.
|
|
- `schema` — PostgreSQL schema.
|
|
- `use_table_cache` — Defines if the database table structure is cached or not. Optional. Default value: `0`.
|
|
|
|
## Data Types Support {#data_types-support}
|
|
|
|
| PostgreSQL | ClickHouse |
|
|
|------------------|--------------------------------------------------------------|
|
|
| DATE | [Date](../../sql-reference/data-types/date.md) |
|
|
| TIMESTAMP | [DateTime](../../sql-reference/data-types/datetime.md) |
|
|
| REAL | [Float32](../../sql-reference/data-types/float.md) |
|
|
| DOUBLE | [Float64](../../sql-reference/data-types/float.md) |
|
|
| DECIMAL, NUMERIC | [Decimal](../../sql-reference/data-types/decimal.md) |
|
|
| SMALLINT | [Int16](../../sql-reference/data-types/int-uint.md) |
|
|
| INTEGER | [Int32](../../sql-reference/data-types/int-uint.md) |
|
|
| BIGINT | [Int64](../../sql-reference/data-types/int-uint.md) |
|
|
| SERIAL | [UInt32](../../sql-reference/data-types/int-uint.md) |
|
|
| BIGSERIAL | [UInt64](../../sql-reference/data-types/int-uint.md) |
|
|
| TEXT, CHAR | [String](../../sql-reference/data-types/string.md) |
|
|
| INTEGER | Nullable([Int32](../../sql-reference/data-types/int-uint.md))|
|
|
| ARRAY | [Array](../../sql-reference/data-types/array.md) |
|
|
|
|
|
|
## Examples of Use {#examples-of-use}
|
|
|
|
Database in ClickHouse, exchanging data with the PostgreSQL server:
|
|
|
|
``` sql
|
|
CREATE DATABASE test_database
|
|
ENGINE = PostgreSQL('postgres1:5432', 'test_database', 'postgres', 'mysecretpassword', 'schema_name',1);
|
|
```
|
|
|
|
``` sql
|
|
SHOW DATABASES;
|
|
```
|
|
|
|
``` text
|
|
┌─name──────────┐
|
|
│ default │
|
|
│ test_database │
|
|
│ system │
|
|
└───────────────┘
|
|
```
|
|
|
|
``` sql
|
|
SHOW TABLES FROM test_database;
|
|
```
|
|
|
|
``` text
|
|
┌─name───────┐
|
|
│ test_table │
|
|
└────────────┘
|
|
```
|
|
|
|
Reading data from the PostgreSQL table:
|
|
|
|
``` sql
|
|
SELECT * FROM test_database.test_table;
|
|
```
|
|
|
|
``` text
|
|
┌─id─┬─value─┐
|
|
│ 1 │ 2 │
|
|
└────┴───────┘
|
|
```
|
|
|
|
Writing data to the PostgreSQL table:
|
|
|
|
``` sql
|
|
INSERT INTO test_database.test_table VALUES (3,4);
|
|
SELECT * FROM test_database.test_table;
|
|
```
|
|
|
|
``` text
|
|
┌─int_id─┬─value─┐
|
|
│ 1 │ 2 │
|
|
│ 3 │ 4 │
|
|
└────────┴───────┘
|
|
```
|
|
|
|
Consider the table structure was modified in PostgreSQL:
|
|
|
|
``` sql
|
|
postgre> ALTER TABLE test_table ADD COLUMN data Text
|
|
```
|
|
|
|
As the `use_table_cache` parameter was set to `1` when the database was created, the table structure in ClickHouse was cached and therefore not modified:
|
|
|
|
``` sql
|
|
DESCRIBE TABLE test_database.test_table;
|
|
```
|
|
``` text
|
|
┌─name───┬─type──────────────┐
|
|
│ id │ Nullable(Integer) │
|
|
│ value │ Nullable(Integer) │
|
|
└────────┴───────────────────┘
|
|
```
|
|
|
|
After detaching the table and attaching it again, the structure was updated:
|
|
|
|
``` sql
|
|
DETACH TABLE test_database.test_table;
|
|
ATTACH TABLE test_database.test_table;
|
|
DESCRIBE TABLE test_database.test_table;
|
|
```
|
|
``` text
|
|
┌─name───┬─type──────────────┐
|
|
│ id │ Nullable(Integer) │
|
|
│ value │ Nullable(Integer) │
|
|
│ data │ Nullable(String) │
|
|
└────────┴───────────────────┘
|
|
```
|
|
|
|
## Related content
|
|
|
|
- Blog: [ClickHouse and PostgreSQL - a match made in data heaven - part 1](https://clickhouse.com/blog/migrating-data-between-clickhouse-postgres)
|