From 5efd604ec0a3bdde98fe19d8cada69ab4ef80db3 Mon Sep 17 00:00:00 2001 From: Alvaro Herrera Date: Tue, 4 Jun 2019 16:42:40 -0400 Subject: [PATCH] Document piecemeal construction of partitioned indexes MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Continuous operation cannot be achieved without applying this technique, so it needs to be properly described. Author: Álvaro Herrera Reported-by: Tom Lane Discussion: https://postgr.es/m/8756.1556302759@sss.pgh.pa.us --- doc/src/sgml/ddl.sgml | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml index 5fe5f86402..cce1618fc1 100644 --- a/doc/src/sgml/ddl.sgml +++ b/doc/src/sgml/ddl.sgml @@ -3948,6 +3948,44 @@ ALTER TABLE measurement ATTACH PARTITION measurement_y2008m02 One may then drop the constraint after ATTACH PARTITION is finished, because it is no longer necessary. + + + As explained above, it is possible to create indexes on partitioned tables + and they are applied automatically to the entire hierarchy. This is very + convenient, as not only the existing partitions will become indexed, but + also any partitions that are created in the future will. One limitation is + that it's not possible to use the CONCURRENTLY + qualifier when creating such a partitioned index. To overcome long lock + times, it is possible to use CREATE INDEX ON ONLY + the partitioned table; such an index is marked invalid, and the partitions + do not get the index applied automatically. The indexes on partitions can + be created separately using CONCURRENTLY, and later + attached to the index on the parent using + ALTER INDEX .. ATTACH PARTITION. Once indexes for all + partitions are attached to the parent index, the parent index is marked + valid automatically. Example: + +CREATE INDEX measurement_usls_idx ON ONLY measurement (unitsales); + +CREATE INDEX measurement_usls_200602_idx + ON measurement_y2006m02 (unitsales); +ALTER INDEX measurement_usls_idx + ATTACH PARTITION measurement_usls_200602_idx; +... + + + This technique can be used with UNIQUE and + PRIMARY KEY constraints too; the indexes are created + implicitly when the constraint is created. Example: + +ALTER TABLE ONLY measurement ADD UNIQUE (city_id, logdate); + +ALTER TABLE measurement_y2006m02 ADD UNIQUE (city_id, logdate); +ALTER INDEX measurement_city_id_logdate_key + ATTACH PARTITION measurement_y2006m02_city_id_logdate_key; +... + +