mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-12-12 17:32:32 +00:00
139 lines
5.0 KiB
Markdown
139 lines
5.0 KiB
Markdown
---
|
|
slug: /en/sql-reference/table-functions/postgresql
|
|
sidebar_position: 42
|
|
sidebar_label: postgresql
|
|
---
|
|
|
|
# postgresql
|
|
|
|
Allows `SELECT` and `INSERT` queries to be performed on data that is stored on a remote PostgreSQL server.
|
|
|
|
**Syntax**
|
|
|
|
``` sql
|
|
postgresql('host:port', 'database', 'table', 'user', 'password'[, `schema`])
|
|
```
|
|
|
|
**Arguments**
|
|
|
|
- `host:port` — PostgreSQL server address.
|
|
- `database` — Remote database name.
|
|
- `table` — Remote table name.
|
|
- `user` — PostgreSQL user.
|
|
- `password` — User password.
|
|
- `schema` — Non-default table schema. Optional.
|
|
|
|
**Returned Value**
|
|
|
|
A table object with the same columns as the original PostgreSQL table.
|
|
|
|
:::note
|
|
In the `INSERT` query to distinguish table function `postgresql(...)` from table name with column names list you must use keywords `FUNCTION` or `TABLE FUNCTION`. See examples below.
|
|
:::
|
|
|
|
## Implementation Details
|
|
|
|
`SELECT` queries on PostgreSQL side run as `COPY (SELECT ...) TO STDOUT` inside read-only PostgreSQL transaction with commit after each `SELECT` query.
|
|
|
|
Simple `WHERE` clauses such as `=`, `!=`, `>`, `>=`, `<`, `<=`, and `IN` are executed on the PostgreSQL server.
|
|
|
|
All joins, aggregations, sorting, `IN [ array ]` conditions and the `LIMIT` sampling constraint are executed in ClickHouse only after the query to PostgreSQL finishes.
|
|
|
|
`INSERT` queries on PostgreSQL side run as `COPY "table_name" (field1, field2, ... fieldN) FROM STDIN` inside PostgreSQL transaction with auto-commit after each `INSERT` statement.
|
|
|
|
PostgreSQL Array types converts into ClickHouse arrays.
|
|
|
|
:::note
|
|
Be careful, in PostgreSQL an array data type column like Integer[] may contain arrays of different dimensions in different rows, but in ClickHouse it is only allowed to have multidimensional arrays of the same dimension in all rows.
|
|
:::
|
|
|
|
Supports multiple replicas that must be listed by `|`. For example:
|
|
|
|
```sql
|
|
SELECT name FROM postgresql(`postgres{1|2|3}:5432`, 'postgres_database', 'postgres_table', 'user', 'password');
|
|
```
|
|
|
|
or
|
|
|
|
```sql
|
|
SELECT name FROM postgresql(`postgres1:5431|postgres2:5432`, 'postgres_database', 'postgres_table', 'user', 'password');
|
|
```
|
|
|
|
Supports replicas priority for PostgreSQL dictionary source. The bigger the number in map, the less the priority. The highest priority is `0`.
|
|
|
|
**Examples**
|
|
|
|
Table in PostgreSQL:
|
|
|
|
``` text
|
|
postgres=# CREATE TABLE "public"."test" (
|
|
"int_id" SERIAL,
|
|
"int_nullable" INT NULL DEFAULT NULL,
|
|
"float" FLOAT NOT NULL,
|
|
"str" VARCHAR(100) NOT NULL DEFAULT '',
|
|
"float_nullable" FLOAT NULL DEFAULT NULL,
|
|
PRIMARY KEY (int_id));
|
|
|
|
CREATE TABLE
|
|
|
|
postgres=# INSERT INTO test (int_id, str, "float") VALUES (1,'test',2);
|
|
INSERT 0 1
|
|
|
|
postgresql> SELECT * FROM test;
|
|
int_id | int_nullable | float | str | float_nullable
|
|
--------+--------------+-------+------+----------------
|
|
1 | | 2 | test |
|
|
(1 row)
|
|
```
|
|
|
|
Selecting data from ClickHouse:
|
|
|
|
```sql
|
|
SELECT * FROM postgresql('localhost:5432', 'test', 'test', 'postgresql_user', 'password') WHERE str IN ('test');
|
|
```
|
|
|
|
``` text
|
|
┌─int_id─┬─int_nullable─┬─float─┬─str──┬─float_nullable─┐
|
|
│ 1 │ ᴺᵁᴸᴸ │ 2 │ test │ ᴺᵁᴸᴸ │
|
|
└────────┴──────────────┴───────┴──────┴────────────────┘
|
|
```
|
|
|
|
Inserting:
|
|
|
|
```sql
|
|
INSERT INTO TABLE FUNCTION postgresql('localhost:5432', 'test', 'test', 'postgrsql_user', 'password') (int_id, float) VALUES (2, 3);
|
|
SELECT * FROM postgresql('localhost:5432', 'test', 'test', 'postgresql_user', 'password');
|
|
```
|
|
|
|
``` text
|
|
┌─int_id─┬─int_nullable─┬─float─┬─str──┬─float_nullable─┐
|
|
│ 1 │ ᴺᵁᴸᴸ │ 2 │ test │ ᴺᵁᴸᴸ │
|
|
│ 2 │ ᴺᵁᴸᴸ │ 3 │ │ ᴺᵁᴸᴸ │
|
|
└────────┴──────────────┴───────┴──────┴────────────────┘
|
|
```
|
|
|
|
Using Non-default Schema:
|
|
|
|
```text
|
|
postgres=# CREATE SCHEMA "nice.schema";
|
|
|
|
postgres=# CREATE TABLE "nice.schema"."nice.table" (a integer);
|
|
|
|
postgres=# INSERT INTO "nice.schema"."nice.table" SELECT i FROM generate_series(0, 99) as t(i)
|
|
```
|
|
|
|
```sql
|
|
CREATE TABLE pg_table_schema_with_dots (a UInt32)
|
|
ENGINE PostgreSQL('localhost:5432', 'clickhouse', 'nice.table', 'postgrsql_user', 'password', 'nice.schema');
|
|
```
|
|
|
|
**See Also**
|
|
|
|
- [The PostgreSQL table engine](../../engines/table-engines/integrations/postgresql.md)
|
|
- [Using PostgreSQL as a dictionary source](../../sql-reference/dictionaries/index.md#dictionary-sources#dicts-external_dicts_dict_sources-postgresql)
|
|
|
|
## Related content
|
|
|
|
- Blog: [ClickHouse and PostgreSQL - a match made in data heaven - part 1](https://clickhouse.com/blog/migrating-data-between-clickhouse-postgres)
|
|
- Blog: [ClickHouse and PostgreSQL - a Match Made in Data Heaven - part 2](https://clickhouse.com/blog/migrating-data-between-clickhouse-postgres-part-2)
|