cp sql/ from GNU Taler exchange

include/sql/0002-revolving_work_shards.sql

@@ -0,0 +1,46 @@
+--
+-- This file is part of TALER
+-- Copyright (C) 2014--2022 Taler Systems SA
+--
+-- TALER is free software; you can redistribute it and/or modify it under the
+-- terms of the GNU General Public License as published by the Free Software
+-- Foundation; either version 3, or (at your option) any later version.
+--
+-- TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+-- WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+-- A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+--
+-- You should have received a copy of the GNU General Public License along with
+-- TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+--
+
+CREATE UNLOGGED TABLE revolving_work_shards
+  (shard_serial_id BIGINT GENERATED BY DEFAULT AS IDENTITY UNIQUE
+  ,last_attempt INT8 NOT NULL
+  ,start_row INT4 NOT NULL
+  ,end_row INT4 NOT NULL
+  ,active BOOLEAN NOT NULL DEFAULT FALSE
+  ,job_name TEXT NOT NULL
+  ,PRIMARY KEY (job_name, start_row)
+  );
+COMMENT ON TABLE revolving_work_shards
+  IS 'coordinates work between multiple processes working on the same job with partitions that need to be repeatedly processed; unlogged because on system crashes the locks represented by this table will have to be cleared anyway, typically using "taler-exchange-dbinit -s"';
+COMMENT ON COLUMN revolving_work_shards.shard_serial_id
+  IS 'unique serial number identifying the shard';
+COMMENT ON COLUMN revolving_work_shards.last_attempt
+  IS 'last time a worker attempted to work on the shard';
+COMMENT ON COLUMN revolving_work_shards.active
+  IS 'set to TRUE when a worker is active on the shard';
+COMMENT ON COLUMN revolving_work_shards.start_row
+  IS 'row at which the shard scope starts, inclusive';
+COMMENT ON COLUMN revolving_work_shards.end_row
+  IS 'row at which the shard scope ends, exclusive';
+COMMENT ON COLUMN revolving_work_shards.job_name
+  IS 'unique name of the job the workers on this shard are performing';
+
+CREATE INDEX revolving_work_shards_by_job_name_active_last_attempt_index
+  ON revolving_work_shards
+  (job_name
+  ,active
+  ,last_attempt
+  );