---------------------------------------------------------------------------
--
-- complex.sql-
-- This file shows how to create a new user-defined type and how to
-- use this new type.
--
--
-- Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
-- Portions Copyright (c) 1994, Regents of the University of California
--
-- src/tutorial/complex.source
--
---------------------------------------------------------------------------
-----------------------------
-- Creating a new type:
-- We are going to create a new type called 'complex' which represents
-- complex numbers.
-- A user-defined type must have an input and an output function, and
-- optionally can have binary input and output functions. All of these
-- are usually user-defined C functions.
-----------------------------
-- Assume the user defined functions are in _OBJWD_/complex$DLSUFFIX
-- (we do not want to assume this is in the dynamic loader search path).
-- Look at $PWD/complex.c for the source. Note that we declare all of
-- them as STRICT, so we do not need to cope with NULL inputs in the
-- C code. We also mark them IMMUTABLE, since they always return the
-- same outputs given the same inputs.
-- the input function 'complex_in' takes a null-terminated string (the
-- textual representation of the type) and turns it into the internal
-- (in memory) representation. You will get a message telling you 'complex'
-- does not exist yet but that's okay.
CREATE FUNCTION complex_in(cstring)
RETURNS complex
AS '_OBJWD_/complex'
LANGUAGE C IMMUTABLE STRICT;
-- the output function 'complex_out' takes the internal representation and
-- converts it into the textual representation.
CREATE FUNCTION complex_out(complex)
RETURNS cstring
AS '_OBJWD_/complex'
LANGUAGE C IMMUTABLE STRICT;
-- the binary input function 'complex_recv' takes a StringInfo buffer
-- and turns its contents into the internal representation.
CREATE FUNCTION complex_recv(internal)
RETURNS complex
AS '_OBJWD_/complex'
LANGUAGE C IMMUTABLE STRICT;
-- the binary output function 'complex_send' takes the internal representation
-- and converts it into a (hopefully) platform-independent bytea string.
CREATE FUNCTION complex_send(complex)
RETURNS bytea
AS '_OBJWD_/complex'
LANGUAGE C IMMUTABLE STRICT;
-- now, we can create the type. The internallength specifies the size of the
-- memory block required to hold the type (we need two 8-byte doubles).
CREATE TYPE complex (
internallength = 16,
input = complex_in,
output = complex_out,
receive = complex_recv,
send = complex_send,
alignment = double
);
-----------------------------
-- Using the new type:
-- user-defined types can be used like ordinary built-in types.
-----------------------------
-- eg. we can use it in a table
CREATE TABLE test_complex (
a complex,
b complex
);
-- data for user-defined types are just strings in the proper textual
-- representation.
INSERT INTO test_complex VALUES ('(1.0, 2.5)', '(4.2, 3.55 )');
INSERT INTO test_complex VALUES ('(33.0, 51.4)', '(100.42, 93.55)');
SELECT * FROM test_complex;
-----------------------------
-- Creating an operator for the new type:
-- Let's define an add operator for complex types. Since POSTGRES
-- supports function overloading, we'll use + as the add operator.
-- (Operator names can be reused with different numbers and types of
-- arguments.)
-----------------------------
-- first, define a function complex_add (also in complex.c)
CREATE FUNCTION complex_add(complex, complex)
RETURNS complex
AS '_OBJWD_/complex'
LANGUAGE C IMMUTABLE STRICT;
-- we can now define the operator. We show a binary operator here but you
-- can also define a prefix operator by omitting the leftarg.
CREATE OPERATOR + (
leftarg = complex,
rightarg = complex,
procedure = complex_add,
commutator = +
);
SELECT (a + b) AS c FROM test_complex;
-- Occasionally, you may find it useful to cast the string to the desired
-- type explicitly. :: denotes a type cast.
SELECT a + '(1.0,1.0)'::complex AS aa,
b + '(1.0,1.0)'::complex AS bb
FROM test_complex;
-----------------------------
-- Creating aggregate functions
-- you can also define aggregate functions. The syntax is somewhat
-- cryptic but the idea is to express the aggregate in terms of state
-- transition functions.
-----------------------------
CREATE AGGREGATE complex_sum (
sfunc = complex_add,
basetype = complex,
stype = complex,
initcond = '(0,0)'
);
SELECT complex_sum(a) FROM test_complex;
-----------------------------
-- Interfacing New Types with Indexes:
-- We cannot define a secondary index (eg. a B-tree) over the new type
-- yet. We need to create all the required operators and support
-- functions, then we can make the operator class.
-----------------------------
-- first, define the required operators
CREATE FUNCTION complex_abs_lt(complex, complex) RETURNS bool
AS '_OBJWD_/complex' LANGUAGE C IMMUTABLE STRICT;
CREATE FUNCTION complex_abs_le(complex, complex) RETURNS bool
AS '_OBJWD_/complex' LANGUAGE C IMMUTABLE STRICT;
CREATE FUNCTION complex_abs_eq(complex, complex) RETURNS bool
AS '_OBJWD_/complex' LANGUAGE C IMMUTABLE STRICT;
CREATE FUNCTION complex_abs_ge(complex, complex) RETURNS bool
AS '_OBJWD_/complex' LANGUAGE C IMMUTABLE STRICT;
CREATE FUNCTION complex_abs_gt(complex, complex) RETURNS bool
AS '_OBJWD_/complex' LANGUAGE C IMMUTABLE STRICT;
CREATE OPERATOR < (
leftarg = complex, rightarg = complex, procedure = complex_abs_lt,
commutator = > , negator = >= ,
restrict = scalarltsel, join = scalarltjoinsel
);
CREATE OPERATOR <= (
leftarg = complex, rightarg = complex, procedure = complex_abs_le,
commutator = >= , negator = > ,
restrict = scalarlesel, join = scalarlejoinsel
);
CREATE OPERATOR = (
leftarg = complex, rightarg = complex, procedure = complex_abs_eq,
commutator = = ,
-- leave out negator since we didn't create <> operator
-- negator = <> ,
restrict = eqsel, join = eqjoinsel
);
CREATE OPERATOR >= (
leftarg = complex, rightarg = complex, procedure = complex_abs_ge,
commutator = <= , negator = < ,
restrict = scalargesel, join = scalargejoinsel
);
CREATE OPERATOR > (
leftarg = complex, rightarg = complex, procedure = complex_abs_gt,
commutator = < , negator = <= ,
restrict = scalargtsel, join = scalargtjoinsel
);
-- create the support function too
CREATE FUNCTION complex_abs_cmp(complex, complex) RETURNS int4
AS '_OBJWD_/complex' LANGUAGE C IMMUTABLE STRICT;
-- now we can make the operator class
CREATE OPERATOR CLASS complex_abs_ops
DEFAULT FOR TYPE complex USING btree AS
OPERATOR 1 < ,
OPERATOR 2 <= ,
OPERATOR 3 = ,
OPERATOR 4 >= ,
OPERATOR 5 > ,
FUNCTION 1 complex_abs_cmp(complex, complex);
-- now, we can define a btree index on complex types. First, let's populate
-- the table. Note that postgres needs many more tuples to start using the
-- btree index during selects.
INSERT INTO test_complex VALUES ('(56.0,-22.5)', '(-43.2,-0.07)');
INSERT INTO test_complex VALUES ('(-91.9,33.6)', '(8.6,3.0)');
CREATE INDEX test_cplx_ind ON test_complex
USING btree(a complex_abs_ops);
SELECT * from test_complex where a = '(56.0,-22.5)';
SELECT * from test_complex where a < '(56.0,-22.5)';
SELECT * from test_complex where a > '(56.0,-22.5)';
-- clean up the example
DROP TABLE test_complex;
DROP TYPE complex CASCADE;
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