Add tasks table (#8)

Author: mbryzek

pending.sql

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+alter table items alter column hash_code drop default;
+drop index items_organization_id_object_id_key;

scripts/20190906-193722.sql

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+drop table if exists public.tasks;
+
+set search_path to public;
+
+create table tasks (
+  id                          text primary key check(util.non_empty_trimmed_string(id)),
+  data                        text not null check(util.non_empty_trimmed_string(data)),
+  priority                    bigint not null check(priority >= 0),
+  num_attempts                bigint not null check(num_attempts >= 0),
+  processed_at                timestamptz,
+  created_at                  timestamptz not null default now(),
+  updated_at                  timestamptz not null default now(),
+  updated_by_user_id          text not null check(util.non_empty_trimmed_string(updated_by_user_id)),
+  hash_code                   bigint not null
+);
+
+create index tasks_num_attempts_processed_at_idx on tasks(num_attempts, processed_at);
+
+select schema_evolution_manager.create_updated_at_trigger('public', 'tasks');

scripts/20190906-225730.sql

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+create index on tasks(data) where processed_at is null;

scripts/20190909-173126.sql

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+alter table items add updated_at timestamptz not null default now();
+update items set updated_at = created_at;
+alter table items add hash_code bigint not null default 0;
+select schema_evolution_manager.create_updated_at_trigger('public', 'items');

scripts/20190909-175225.sql

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+create unique index items_object_id_idx on items(object_id);
+create index items_organization_id_idx on items(organization_id);
+