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102 lines
3.7 KiB
Markdown
102 lines
3.7 KiB
Markdown
---
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toc_priority: 42
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toc_title: postgresql
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---
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# postgresql {#postgresql}
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Allows `SELECT` and `INSERT` queries to be performed on data that is stored on a remote PostgreSQL server.
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**Syntax**
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``` sql
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postgresql('host:port', 'database', 'table', 'user', 'password')
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```
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**Arguments**
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- `host:port` — PostgreSQL server address.
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- `database` — Remote database name.
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- `table` — Remote table name.
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- `user` — PostgreSQL user.
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- `password` — User password.
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SELECT Queries on PostgreSQL side run as `COPY (SELECT ...) TO STDOUT` inside read-only PostgreSQL transaction with commit after each `SELECT` query.
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Simple `WHERE` clauses such as `=, !=, >, >=, <, <=, IN` are executed on the PostgreSQL server.
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All joins, aggregations, sorting, `IN [ array ]` conditions and the `LIMIT` sampling constraint are executed in ClickHouse only after the query to PostgreSQL finishes.
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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.
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PostgreSQL Array types converts into ClickHouse arrays.
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Be careful in PostgreSQL an array data created like type_name[] may contain multi-dimensional arrays of different dimensions in different rows in same column, but in ClickHouse only allows multi-dimensional arrays of the same count of dimension in all rows in same column in table.
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**Returned Value**
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A table object with the same columns as the original PostgreSQL table.
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!!! info "Note"
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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.
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**Examples**
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Table in PostgreSQL:
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``` text
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postgres=# CREATE TABLE "public"."test" (
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"int_id" SERIAL,
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"int_nullable" INT NULL DEFAULT NULL,
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"float" FLOAT NOT NULL,
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"str" VARCHAR(100) NOT NULL DEFAULT '',
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"float_nullable" FLOAT NULL DEFAULT NULL,
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PRIMARY KEY (int_id));
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CREATE TABLE
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postgres=# insert into test (int_id, str, "float") VALUES (1,'test',2);
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INSERT 0 1
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postgresql> select * from test;
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int_id | int_nullable | float | str | float_nullable
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--------+--------------+-------+------+----------------
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1 | | 2 | test |
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(1 row)
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```
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Selecting data from ClickHouse:
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```sql
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SELECT * FROM postgresql('localhost:5432', 'test', 'test', 'postgresql_user', 'password') WHERE str IN ('test');
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```
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``` text
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┌─int_id─┬─int_nullable─┬─float─┬─str──┬─float_nullable─┐
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│ 1 │ ᴺᵁᴸᴸ │ 2 │ test │ ᴺᵁᴸᴸ │
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└────────┴──────────────┴───────┴──────┴────────────────┘
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```
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Inserting:
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```sql
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INSERT INTO TABLE FUNCTION postgresql('localhost:5432', 'test', 'test', 'postgrsql_user', 'password') (int_id, float) VALUES (2, 3);
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SELECT * FROM postgresql('localhost:5432', 'test', 'test', 'postgresql_user', 'password');
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```
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``` text
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┌─int_id─┬─int_nullable─┬─float─┬─str──┬─float_nullable─┐
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│ 1 │ ᴺᵁᴸᴸ │ 2 │ test │ ᴺᵁᴸᴸ │
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│ 2 │ ᴺᵁᴸᴸ │ 3 │ │ ᴺᵁᴸᴸ │
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└────────┴──────────────┴───────┴──────┴────────────────┘
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```
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**See Also**
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- [The ‘PostgreSQL’ table engine](../../engines/table-engines/integrations/postgresql.md)
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- [Using PostgreSQL as a source of external dictionary](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-sources.md#dicts-external_dicts_dict_sources-postgresql)
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