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  1. MariaDB Server
  2. MDEV-6259

DELETE with OFFSET

        Details

        • Type: Task
        • Status: Open
        • Priority: Major
        • Resolution: Unresolved
        • Fix Version/s: 10.2
        • Component/s: None
        • Labels:
          None

          Description

          Allow DELETE statment with OFFSET, this allow a DELETE like SQLITE:
          http://www.sqlite.org/lang_delete.html

          it's interesting with history table applications where a fixed number of rows is wanted, for example

          CREATE TABLE history (
 channel_id INT NOT NULL DEFAULT 0,
 date_unix DECIMAL(22,6) NOT NULL DEFAULT 0,
 value DECIMAL(22,7) NOT NULL DEFAULT 0,
 PRIMARY KEY (channel_id,date_unix)
);

          many inserts....

          INSERT INTO history (1,now(),current_temperature);
INSERT INTO history (1,now(),current_temperature);
INSERT INTO history (1,now(),current_temperature);
INSERT INTO history (1,now(),current_temperature);
.....

          an crond job executed at every hour:

          DELETE FROM history WHERE channel_id=1 ORDER BY date_unix DESC LIMIT -1 OFFSET 5000

          from SQLITE: A negative LIMIT value is interpreted as "no limit".

          this will remove all rows from this 'channel' that are older than the 5000th row

          —
          today this should be done with two queries:

          SELECT date_unix FROM history WHERE channel_id=1 ORDER BY date_unix DESC LIMIT 1 OFFSET 5000

          get the date_unix value, and execute:

          DELETE FROM history WHERE channel_id=1 AND date_unix<"{$date_unix from previous query$}"

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                  • Assignee:
                    Unassigned
                    Reporter:
                    rspadim roberto spadim
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                    • Created:
                      Updated: