ClickHouse/docs/en/sql-reference/table-functions/postgresql.md

---
toc_priority: 42
toc_title: postgresql
---

# 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.

!!! info "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 {#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.

!!! info "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 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 source of external dictionary](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-sources.md#dicts-external_dicts_dict_sources-postgresql)

[Original article](https://clickhouse.tech/docs/en/sql-reference/table-functions/postgresql/) <!--hide-->