synapse-product/synapse/storage/schema/main/delta/60/01recreate_stream_ordering.sql.postgres

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-- This migration handles the process of changing the type of `stream_ordering` to
-- a BIGINT.
--
-- Note that this is only a problem on postgres as sqlite only has one "integer" type
-- which can cope with values up to 2^63.

-- First add a new column to contain the bigger stream_ordering
ALTER TABLE events ADD COLUMN stream_ordering2 BIGINT;

-- Create a rule which will populate it for new rows.
CREATE OR REPLACE RULE "populate_stream_ordering2" AS
    ON INSERT TO events
    DO UPDATE events SET stream_ordering2=NEW.stream_ordering WHERE stream_ordering=NEW.stream_ordering;

-- Start a bg process to populate it for old events
INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
  (6001, 'populate_stream_ordering2', '{}');

-- ... and another to build an index on it
INSERT INTO background_updates (ordering, update_name, progress_json, depends_on) VALUES
  (6001, 'index_stream_ordering2', '{}', 'populate_stream_ordering2');

-- ... and another to do the switcheroo
INSERT INTO background_updates (ordering, update_name, progress_json, depends_on) VALUES
  (6001, 'replace_stream_ordering_column', '{}', 'index_stream_ordering2');