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133 lines
4.8 KiB
Markdown
133 lines
4.8 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'[, `schema`])
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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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- `schema` — Non-default table schema. Optional.
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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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## Implementation Details {#implementation-details}
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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 `=`, `!=`, `>`, `>=`, `<`, `<=`, and `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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!!! info "Note"
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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.
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Supports multiple replicas that must be listed by `|`. For example:
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```sql
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SELECT DISTINCT(name) FROM postgresql(`postgres{1|2|3}:5432`, 'clickhouse', 'test_replicas', 'postgres', 'mysecretpassword');
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```
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or
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```sql
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SELECT DISTINCT(name) FROM postgresql(`postgres2:5431|postgres3:5432`, 'clickhouse', 'test_replicas', 'postgres', 'mysecretpassword');
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```
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Supports replicas priority for PostgreSQL dictionary source. The bigger the number in map, the less the priority. The highest priority is `0`.
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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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Using Non-default Schema:
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```text
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postgres=# CREATE SCHEMA "nice.schema";
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postgres=# CREATE TABLE "nice.schema"."nice.table" (a integer);
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postgres=# INSERT INTO "nice.schema"."nice.table" SELECT i FROM generate_series(0, 99) as t(i)
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```
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```sql
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CREATE TABLE pg_table_schema_with_dots (a UInt32)
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ENGINE PostgreSQL('localhost:5432', 'clickhouse', 'nice.table', 'postgrsql_user', 'password', 'nice.schema');
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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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[Original article](https://clickhouse.tech/docs/en/sql-reference/table-functions/postgresql/) <!--hide-->
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