Commits on Nov 27, 2024

1. Dynamic Table. …

   Dynamic Table is a an auto-refreshing materialized view which could
   be constructed by base tables, external tables, materialized views
   and dynamic tables.
   And it could be used to answer query by AQUMV.
   As normal tables in CBDB, dynamic tables could also have distribution
   keys.
   
   The purpose of Dynamic Tables is to solve the problem often raised by
   customers who are big fans of a lakehouse architecture: how can we run
   queries on external tables as fast as internal tables?
   
   CREATE DYNAMIC TABLE:
   
   CREATE DYNAMIC TABLE dt0 SCHEDULE '5 * * * *' AS
     SELECT a, b, sum(c) FROM t1 GROUP BY a, b WITH NO DATA DISTRIBUTED
   BY(b);
   CREATE DYNAMIC TABLE
   
   \d
                    List of relations
    Schema | Name |     Type      |  Owner  | Storage
   --------+------+---------------+---------+---------
    public | dt0  | dynamic table | gpadmin | heap
    public | t1   | table         | gpadmin | heap
   (2 rows)
   
   CREATE DYNAMIC TABLE xxx AS Query
   The Query allows any valid SELECT SQL of Materialized Views: from single
   or multiple relations, base tables, materialized views, and dynamic
   tables as well, joins, subquery, aggregation, group by and etc.
   
   SCHEDULE:
   A string used to schedule background job which auto-refreshes the
   dynamic table.
   We follow the valid string of pg_cron extension which supports linux
   crontab, refer https://crontab.guru
   
    ┌───────────── min (0 - 59)
    │ ┌────────────── hour (0 - 23)
    │ │ ┌─────────────── day of month (1 - 31) or last day of the month ($)
    │ │ │ ┌──────────────── month (1 - 12)
    │ │ │ │ ┌───────────────── day of week (0 - 6) (0 to 6 are Sunday to
    │ │ │ │ │                  Saturday, or use names; 7 is also Sunday)
    │ │ │ │ │
    │ │ │ │ │
    * * * * *
   
   You can also use '[1-59] seconds' to schedule a job based on an
   interval.
   The example creates a cron job refreshing the dynamic table at minute 5
   of each hour.
   For convenience, SCHEDULE is optional. If user didn't specific it, a default
   schedule is provided: at every 5th minute.
   
   WITH NO DATA:
   Same as Materialized View, will create an empty Dynamic Table if
   specified.
   
   DISTRIBUTED BY:
   Same as normal tables in CBDB, Dynamic Tables could support distribution
   keys as materialized views.
   
   Refresh Dynamic Table
   As seen in pg_task, we put a command to auto-refresh dynamic tables.
   However, if users want to do a REFRESH manually, exec command REFRESH
   DYNAMIC TABLE is also supported.
   REFRESH DYNAMIC TABLE dt0;
   REFRESH DYNAMIC TABLE
   
   Refresh WITH NO DATA
   Same as Materialized Views, Refresh with no data will truncate the
   Dynamic Table and make it unpopulated status.
   REFRESH DYNAMIC TABLE dt0 WITH NO DATA;
   REFRESH DYNAMIC TABLE
   
   Drop Dynamic Table
   Drop a Dynamic Table will drop its scheduler job automatically.
   DROP DYNAMIC TABLE dt0;
   DROP DYNAMIC TABLE
   
   Like Materialized Views, Dynamic Tables could be used to answer query
   too. This is limited by AQUMV.
   
   Authored-by: Zhang Mingli [email protected]

   

   avamingli committed Nov 27, 2024
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