ClickHouse/docs/en/sql-reference/table-functions/postgresql.md
2023-04-10 15:23:00 +01:00

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---
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)