5af066578a
The goal is to make the available defaults safe for future use, as they are often taken from existing config files or documentation verbatim. Referenced issue: #14290 Closes scylladb/scylladb#15947
133 lines
5.5 KiB
ReStructuredText
133 lines
5.5 KiB
ReStructuredText
.. highlight:: cql
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.. _delete_statement:
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DELETE
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^^^^^^
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Deleting rows or parts of rows uses the ``DELETE`` statement:
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.. code-block::
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delete_statement: DELETE [ `simple_selection` ( ',' `simple_selection` ) ]
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: FROM `table_name`
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: [ USING `update_parameter` ( AND `update_parameter` )* ]
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: WHERE `where_clause`
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: [ IF ( EXISTS | `condition` ( AND `condition` )* ) ]
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For instance:
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.. code-block:: cql
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DELETE FROM NerdMovies USING TIMESTAMP 1240003134000000
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WHERE movie = 'Serenity';
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DELETE phone FROM Users
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WHERE userid IN (C73DE1D3-AF08-40F3-B124-3FF3E5109F22, B70DE1D0-9908-4AE3-BE34-5573E5B09F14);
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The ``DELETE`` statement deletes columns and rows. If column names are provided directly after the ``DELETE`` keyword,
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only those columns are deleted from the row indicated by the ``WHERE`` clause. Otherwise, whole rows are removed.
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The ``WHERE`` clause specifies which rows are to be deleted. Multiple rows may be deleted with one statement by using an
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``IN`` operator. A range of rows may be deleted using an inequality operator (such as ``>=``).
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``DELETE`` supports the ``TIMESTAMP`` option with the same semantics as the TIMESTAMP parameter used in the ``UPDATE`` statement.
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The ``DELETE`` statement deletes data written with :ref:`INSERT <insert-statement>` or :ref:`UPDATE <update-statement>` (or :ref:`BATCH <batch_statement>`)
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using a timestamp that is less than or equal to the ``DELETE`` timestamp.
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For more information on the :token:`update_parameter` refer to the :ref:`UPDATE <update-parameters>` section.
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In a ``DELETE`` statement, all deletions within the same partition key are applied atomically,
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meaning either all columns mentioned in the statement are deleted or none.
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If ``DELETE`` statement has the same timestamp as ``INSERT`` or
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``UPDATE`` of the same primary key, delete operation prevails (see :ref:`update ordering <update-ordering>`).
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A ``DELETE`` operation can be conditional through the use of an ``IF`` clause, similar to ``UPDATE`` and ``INSERT``
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statements. Each such ``DELETE`` gets a globally unique timestamp.
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However, as with ``INSERT`` and ``UPDATE`` statements, this will incur a non-negligible performance cost
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(internally, Paxos will be used) and so should be used sparingly.
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Please refer to the :ref:`update parameters <update-parameters>` section for more information on the :token:`update_parameter`.
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Range deletions
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~~~~~~~~~~~~~~~
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Range deletions allow you to delete rows from a single partition, given that the clustering key is within the given range. The delete request can be determined on both ends, or it can be open-ended.
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.. _open-range-deletions:
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Open range deletions
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~~~~~~~~~~~~~~~~~~~~
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Open range deletions delete rows based on an open-ended request (>, <, >=, =<, etc.)
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For example, suppose your data set for events at Madison Square Garden includes:
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.. code-block:: none
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CREATE KEYSPACE mykeyspace WITH replication = {'class': 'NetworkTopologyStrategy', 'replication_factor': '3'} AND durable_writes = true;
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use mykeyspace ;
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CREATE TABLE events ( id text, created_at date, content text, PRIMARY KEY (id, created_at) );
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INSERT into events (id, created_at, content) VALUES ('concert', '2019-11-19', 'SuperM');
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INSERT into events (id, created_at, content) VALUES ('concert', '2019-11-15', 'Billy Joel');
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INSERT into events (id, created_at, content) VALUES ('game', '2019-11-03', 'Knicks v Sacramento');
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INSERT into events (id, created_at, content) VALUES ('concert', '2019-10-31', 'Dead & Company');
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INSERT into events (id, created_at, content) VALUES ('game', '2019-10-28', 'Knicks v Chicago');
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INSERT into events (id, created_at, content) VALUES ('concert', '2019-10-25', 'Billy Joel');
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SELECT * from events;
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id | created_at | content
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---------+------------+---------------------
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game | 2019-10-28 | Knicks v Chicago
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game | 2019-11-03 | Knicks v Sacramento
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concert | 2019-10-25 | Billy Joel
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concert | 2019-10-31 | Dead & Company
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concert | 2019-11-15 | Billy Joel
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concert | 2019-11-19 | SuperM
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(6 rows)
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And you wanted to delete all of the concerts from the month of October using an open-ended range delete. You would run:
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.. code-block:: none
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DELETE FROM events WHERE id='concert' AND created_at <= '2019-10-31';
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SELECT * from events;
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id | created_at | content
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---------+------------+---------------------
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game | 2019-10-28 | Knicks v Chicago
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game | 2019-11-03 | Knicks v Sacramento
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concert | 2019-11-15 | Billy Joel
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concert | 2019-11-19 | SuperM
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(4 rows)
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:doc:`Apache Cassandra Query Language (CQL) Reference </cql/index>`
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.. include:: /rst_include/apache-copyrights.rst
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.. Licensed to the Apache Software Foundation (ASF) under one
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.. or more contributor license agreements. See the NOTICE file
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.. distributed with this work for additional information
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.. regarding copyright ownership. The ASF licenses this file
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.. to you under the Apache License, Version 2.0 (the
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.. "License"); you may not use this file except in compliance
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.. with the License. You may obtain a copy of the License at
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..
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.. http://www.apache.org/licenses/LICENSE-2.0
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..
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.. Unless required by applicable law or agreed to in writing, software
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.. distributed under the License is distributed on an "AS IS" BASIS,
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.. WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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.. See the License for the specific language governing permissions and
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.. limitations under the License.
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