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<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<extra-ddl xmlns="http://ebean-orm.github.io/xml/ns/extraddl">
<ddl-script name="partition help" init="true" platforms="postgres">
-- partitioning helper functions (UTC based)
------------------------------------------------------------------------------------
-- Type: partition_meta
--
-- Type used to hold common partitioning parameters such as period start and end etc
------------------------------------------------------------------------------------
do $$
begin
if not exists (select 1 from pg_type where typname = 'partition_meta') THEN
create type partition_meta as
(
period_start timestamptz,
period_end timestamptz,
period_name text,
base_name text,
part_name text
);
end if;
end$$;
------------------------------------------------------------------------------------
-- Function: _partition_create
--
-- Internal helper method to create a partition given meta data
------------------------------------------------------------------------------------
create or replace function _partition_create(meta partition_meta)
returns text
language plpgsql
set timezone to 'UTC'
as $$
begin
execute format('create table if not exists %I partition of %I for values from (''%s'') TO (''%s'')', meta.part_name, meta.base_name, meta.period_start, meta.period_end);
return meta.part_name;
end;
$$;
------------------------------------------------------------------------------------
-- Function: _partition_meta
--
-- Internal helper method to create and return meta data used to create a partition.
-- Helps work out start and end periods for day, week, month and year partitions.
------------------------------------------------------------------------------------
create or replace function _partition_meta(
mode text,
asOf date,
baseName text)
returns partition_meta
language plpgsql
set timezone to 'UTC'
as $$
declare
partName text;
meta partition_meta;
asOfUtc timestamptz;
begin
asOfUtc = timezone('utc', asOf);
if (mode = 'day') then
asOfUtc = date_trunc('day', asOfUtc);
partName = to_char(asOfUtc, 'YYYY_MM_DD');
select asOfUtc, asOfUtc + interval '1 days' into meta.period_start, meta.period_end;
elseif (mode = 'week') then
asOfUtc = date_trunc('week', asOfUtc);
partName = format('%s_w%s', extract(ISOYEAR FROM asOfUtc), extract(WEEK FROM asOfUtc));
select asOfUtc, asOfUtc + interval '7 days' into meta.period_start, meta.period_end;
elseif (mode = 'year') then
asOfUtc = date_trunc('year', asOfUtc);
partName = to_char(date_trunc('year', asOfUtc), 'YYYY');
select asOfUtc, asOfUtc + interval '1 year' into meta.period_start, meta.period_end;
else
asOfUtc = date_trunc('month', asOfUtc);
partName = to_char(asOfUtc, 'YYYY_MM');
select asOfUtc, asOfUtc + interval '1 month' into meta.period_start, meta.period_end;
end if;
select partName, baseName, format('%s_%s', baseName, partName)
into meta.period_name, meta.base_name, meta.part_name;
return meta;
end;
$$;
------------------------------------------------------------------------------------
-- Function: _partition_over
--
-- Internal helper method to return a set/table of dates to ensure partitions exists for.
-- Typically we want to ensure some future partitions exist and this helps return dates
-- for which we loop to create partitions.
------------------------------------------------------------------------------------
create or replace function _partition_over(
mode text,
fromDate date default current_date,
_count integer default 0)
returns TABLE(of_date date)
language plpgsql
as $$
declare
endDate date;
begin
if (mode = 'day') then
endDate = fromDate + (interval '1 day' * _count);
fromDate = fromDate - interval '1 day'; -- allow for timezone
return query select s::date from generate_series(fromDate, endDate, '1 day') s;
elseif (mode = 'week') then
fromDate = date_trunc('week', fromDate);
endDate = fromDate + (interval '1 week' * _count);
return query select s::date from generate_series(fromDate, endDate, '1 week') s;
elseif (mode = 'year') then
fromDate = date_trunc('year', fromDate);
endDate = fromDate + (interval '1 year' * _count);
return query select s::date from generate_series(fromDate, endDate, '1 year') s;
else
fromDate = date_trunc('month', fromDate);
endDate = fromDate + (interval '1 month' * _count);
return query select s::date from generate_series(fromDate, endDate, '1 month') s;
end if;
end;
$$;
------------------------------------------------------------------------------------
-- Function: partition
--
-- Helper to ensure we create partitions into the future as needed for day, week, month
-- and year based partitioning. Typically we call this periodically (e.g. every day).
--
-- Examples:
--
-- select partition('week', 'trip', 4);
-- select partition('month', 'event', 1);
--
------------------------------------------------------------------------------------
create or replace function partition(
mode text, -- one of 'day','week','month','year'
baseName text, -- base table name
partitionCount integer default 0, -- number of additional partitions
fromDate date default current_date) -- date to create first partition for
returns text
language plpgsql
set timezone to 'UTC'
as $$
begin
perform _partition_create(_partition_meta(mode, poDate, baseName))
from _partition_over(mode, fromDate, partitionCount) poDate;
return 'done';
end;
$$;
------------------------------------------------------------------------------------
-- Function: partition_init
--
-- Similar to partition but allows the first partition to be bigger with an explicit
-- initDate typically to allow back dated rows to go into the initial partition.
--
-- Examples:
--
-- select partition_init(date '2001-01-01', 'week', 'event');
--
------------------------------------------------------------------------------------
create or replace function partition_init(
initDate date, -- first partition period start date
mode text, -- one of 'day','week','month','year'
baseName text, -- base table name
partitionCount integer default 0, -- number of additional partitions
fromDate date default current_date) -- date to create first partition for
returns text
language plpgsql
set timezone to 'UTC'
as $$
declare
meta partition_meta;
begin
-- override the period start for the first partition
meta = _partition_meta(mode, fromDate, baseName);
meta.period_start = initDate;
perform _partition_create(meta);
if (partitionCount > 0) then
-- create additional partitions normally
fromDate = fromDate + interval '1 day';
perform _partition_create(_partition_meta(mode, poDate, baseName))
from _partition_over(mode, fromDate, partitionCount) poDate;
end if;
return 'done';
end;
$$;
</ddl-script>
</extra-ddl>