Self-managing PostgreSQL partition tables

Question

I am trying to make a self-managing partition table setup with Postgres. It all revolves around this function but I can\'t seem to get Postgres to accept my table names. Any

Answer 1

You are mixing double precision output of date_part() with text '-'. That doesn't make sense to PostgreSQL. You would need an explicit cast to text. But there is a much simpler way to do all of this:

startdate:=date_part('year',to_timestamp(NEW.date))
||'-'||date_part('month',to_timestamp(NEW.date))
||'-'||date_part('day',to_timestamp(NEW.date));

Use instead:

startdate := to_char(NEW.date, 'YYYY-MM-DD');

This makes no sense either:

EXECUTE 'CREATE TABLE $1 (
        CHECK (date >= DATE $2 AND date < DATE $3 )
    ) INHERITS (pings)' USING quote_ident(tablename),startdate,enddate;

You can only supply values with the USING clause. Read the manual here. Try instead:

EXECUTE 'CREATE TABLE ' || quote_ident(tablename) || ' (
            CHECK ("date" >= ''' || startdate || ''' AND
                   "date" <  ''' || enddate   || '''))
            INHERITS (ping)';

Or better yet, use format(). See below.

Also, like @a_horse answered: You need to put your text values in single quotes.

Similar here:

EXECUTE 'INSERT INTO $1 VALUES (NEW.*)' USING quote_ident(tablename);

Instead:

EXECUTE 'INSERT INTO ' || quote_ident(tablename) || ' VALUES ($1.*)'
USING NEW;

Related answer:

• How to dynamically use TG_TABLE_NAME in PostgreSQL 8.2?

Aside: While "date" is allowed for a column name in PostgreSQL it is a reserved word in every SQL standard. Don't name your column "date", it leads to confusing syntax errors.

Complete working demo

CREATE TABLE ping (ping_id integer, the_date date);

CREATE OR REPLACE FUNCTION trg_ping_partition()
  RETURNS trigger AS
$func$
DECLARE
   _tbl text := to_char(NEW.the_date, '"ping_"YYYY_DDD_') || NEW.ping_id;
BEGIN
   IF NOT EXISTS (
      SELECT 1
      FROM   pg_catalog.pg_class c
      JOIN   pg_catalog.pg_namespace n ON n.oid = c.relnamespace
      WHERE  n.nspname = 'public'  -- your schema
      AND    c.relname = _tbl
      AND    c.relkind = 'r') THEN

      EXECUTE format('CREATE TABLE %I (CHECK (the_date >= %L AND
                                              the_date <  %L)) INHERITS (ping)'
              , _tbl
              , to_char(NEW.the_date,     'YYYY-MM-DD')
              , to_char(NEW.the_date + 1, 'YYYY-MM-DD')
              );
   END IF;

   EXECUTE 'INSERT INTO ' || quote_ident(_tbl) || ' VALUES ($1.*)'
   USING NEW; 

   RETURN NULL;
END
$func$ LANGUAGE plpgsql SET search_path = public;

CREATE TRIGGER insbef
BEFORE INSERT ON ping
FOR EACH ROW EXECUTE PROCEDURE trg_ping_partition();

• Update: Later versions of Postgres have more elegant ways to check if a table exists:

  • How to check if a table exists in a given schema

• to_char() can take a date as $1. That's converted to timestamp automatically.
  The manual on date / time functions.

• (Optionally) SET the search_path for the scope of your function to avoid misconduct with a changed search_path setting.

• Multiple other simplifications and improvements. Compare the code.

Tests:

INSERT INTO ping VALUES (1, now()::date);
INSERT INTO ping VALUES (2, now()::date);
INSERT INTO ping VALUES (2, now()::date + 1);
INSERT INTO ping VALUES (2, now()::date + 1);

SQL Fiddle.