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sql: permit creation and refreshing of materialized views as of system time #56167

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sql: permit creation and refreshing of materialized views as of system time #56167

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Commits on Oct 30, 2020

  1. sql: add support for CTAS AS OF SYSTEM TIME 

    Previously, running a statement of the form

    CREATE TABLE t AS SELECT ... FROM ... AS OF SYSTEM TIME x

was not supported.

Now, it is supported. The semantics are that the table creation happens
at the transaction timestamp, but the backfill that's performed to fetch
the data from the `SELECT` is performed at the user-specified timestamp
x.

This is useful for copying data from tables that are experiencing write
traffic. Reading the contended table's data at a historical timestamp
avoids contention on the CREATE TABLE AS.

Release note (sql change): CREATE TABLE AS SELECT ... FROM ... AS OF
SYSTEM TIME x is now supported.
    @jordanlewis
    jordanlewis committed Oct 30, 2020
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  2. sql: wip: add AOST capabilities to MATVIEWS 

    Add the ability to CREATE and REFRESH MATERIALIZED VIEWS, AS OF SYSTEM
TIME. The purpose of this is to allow the expensive backfill operations
to happen at a timestamp in the past to avoid contention.

Currently, this is a little bit broken, because schema changes of the
backing tables of the views can wreak havoc when performed at different
system times.

Release note (sql change): add AOST capabilities to materialized views.
    @jordanlewis
    jordanlewis committed Oct 30, 2020
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