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 ideas or examples of self-managing partition table trigger functions?

My current function:

DECLARE
day integer;
year integer;
tablename text;
startdate text;
enddate text;
BEGIN
day:=date_part('doy',to_timestamp(NEW.date));
year:=date_part('year',to_timestamp(NEW.date));
tablename:='pings_'||year||'_'||day||'_'||NEW.id;
-- RAISE EXCEPTION 'tablename=%',tablename;
PERFORM 'tablename' FROM pg_tables WHERE 'schemaname'=tablename;
-- RAISE EXCEPTION 'found=%',FOUND;
IF FOUND <> TRUE THEN
    startdate:=date_part('year',to_timestamp(NEW.date))||'-'||date_part('month',to_timestamp(NEW.date))||'-'||date_part('day',to_timestamp(NEW.date));
    enddate:=startdate::timestamp + INTERVAL '1 day';
    EXECUTE 'CREATE TABLE $1 (
        CHECK ( date >= DATE $2 AND date < DATE $3 )
    ) INHERITS (pings)' USING quote_ident(tablename),startdate,enddate;
END IF;
EXECUTE 'INSERT INTO $1 VALUES (NEW.*)' USING quote_ident(tablename);
RETURN NULL;
END;

I want it to auto-create a table called pings_YEAR_DOY_ID but it always fails with:

2011-10-24 13:39:04 CDT [15804]: [1-1] ERROR:  invalid input syntax for type double precision: "-" at character 45
2011-10-24 13:39:04 CDT [15804]: [2-1] QUERY:  SELECT date_part('year',to_timestamp( $1 ))+'-'+date_part('month',to_timestamp( $2 ))+'-'+date_part('day',to_timestamp( $3 ))
2011-10-24 13:39:04 CDT [15804]: [3-1] CONTEXT:  PL/pgSQL function "ping_partition" line 15 at assignment
2011-10-24 13:39:04 CDT [15804]: [4-1] STATEMENT:  INSERT INTO pings VALUES (0,0,5);

TRY 2

After applying the changes and modifying it some more (date is a unixtimestamp column, my thinking being that an integer column is faster than a timestamp column when selecting). I get the below error, not sure if I am using the proper syntax for USING NEW?

Updated function:

CREATE FUNCTION ping_partition() RETURNS trigger
    LANGUAGE plpgsql
    AS $_$DECLARE
day integer;
year integer;
tablename text;
startdate text;
enddate text;
BEGIN
day:=date_part('doy',to_timestamp(NEW.date));
year:=date_part('year',to_timestamp(NEW.date));
tablename:='pings_'||year||'_'||day||'_'||NEW.id;
-- RAISE EXCEPTION 'tablename=%',tablename;
PERFORM 'tablename' FROM pg_tables WHERE 'schemaname'=tablename;
-- RAISE EXCEPTION 'found=%',FOUND;
IF FOUND <> TRUE THEN
    startdate := to_char(to_timestamp(NEW.date), 'YYYY-MM-DD');
    enddate:=startdate::timestamp + INTERVAL '1 day';
    EXECUTE 'CREATE TABLE ' || quote_ident(tablename) || ' (
        CHECK ( date >= EXTRACT(EPOCH FROM DATE ' || quote_literal(startdate) || ')
            AND date < EXTRACT(EPOCH FROM DATE ' || quote_literal(enddate) || ') )
    ) INHERITS (pings)';
END IF;
EXECUTE 'INSERT INTO ' || quote_ident(tablename) || ' SELECT $1' USING NEW; 
RETURN NULL;
END;
$_$;

My statement:

INSERT INTO pings VALUES (0,0,5);

SQL error:

ERROR:  column "date" is of type integer but expression is of type pings
LINE 1: INSERT INTO pings_1969_365_0 SELECT $1
                                            ^
HINT:  You will need to rewrite or cast the expression.
QUERY:  INSERT INTO pings_1969_365_0 SELECT $1
CONTEXT:  PL/pgSQL function "ping_partition" line 22 at EXECUTE statement

Answer 1

Note: Since Postgres 10 declarative partitioning is typically superior to partitioning by inheritance as used in this case.

---

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
  LANGUAGE plpgsql SET client_min_messages = 'WARNING' AS
$func$
DECLARE
   _schema text := 'public';  -- double-quoted if necessary
   _tbl text := to_char(NEW.the_date, '"ping_"YYYY_DDD_') || NEW.ping_id;
BEGIN
   EXECUTE format('CREATE TABLE IF NOT EXISTS %1$s.%2$s
                   (CHECK (the_date >= %3$L
                       AND the_date <  %4$L)) INHERITS (%1$s.ping)'
           , _schema   -- %1$s
           , _tbl      -- %2$s  -- legal(!) name needs no quotes
           , to_char(NEW.the_date,     'YYYY-MM-DD')  -- %3$L
           , to_char(NEW.the_date + 1, 'YYYY-MM-DD')  -- %4$L
           );

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

   RETURN NULL;
END
$func$;

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

Postgres 9.1 added the clause IF NOT EXISTS for CREATE TABLE. See:

• PostgreSQL create table if not exists

Postgres 11 added the more appropriate syntax variant EXECUTE FUNCTION for triggers. Use EXECUTE PROCEDURE in older versions.
See:

• Trigger uses a procedure or a function?

to_char() can take a date as $1. That’s converted to timestamp automatically. See:

• The manual on date / time functions.

I SET client_min_messages = 'WARNING' for the scope of the function to silence the flood of notices that would otherwise be raised on conflict by IF NOT EXISTS.

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);

fiddle
_{OLD sqlfiddle}