postgresql/src/test/regress/sql/case.sql

--
-- CASE
-- Test the case statement
--

CREATE TABLE CASE_TBL (
  i integer,
  f double precision
);

CREATE TABLE CASE2_TBL (
  i integer,
  j integer
);

INSERT INTO CASE_TBL VALUES (1, 10.1);
INSERT INTO CASE_TBL VALUES (2, 20.2);
INSERT INTO CASE_TBL VALUES (3, -30.3);
INSERT INTO CASE_TBL VALUES (4, NULL);

INSERT INTO CASE2_TBL VALUES (1, -1);
INSERT INTO CASE2_TBL VALUES (2, -2);
INSERT INTO CASE2_TBL VALUES (3, -3);
INSERT INTO CASE2_TBL VALUES (2, -4);
INSERT INTO CASE2_TBL VALUES (1, NULL);
INSERT INTO CASE2_TBL VALUES (NULL, -6);

--
-- Simplest examples without tables
--

SELECT '3' AS "One",
  CASE
    WHEN 1 < 2 THEN 3
  END AS "Simple WHEN";

SELECT '<NULL>' AS "One",
  CASE
    WHEN 1 > 2 THEN 3
  END AS "Simple default";

SELECT '3' AS "One",
  CASE
    WHEN 1 < 2 THEN 3
    ELSE 4
  END AS "Simple ELSE";

SELECT '4' AS "One",
  CASE
    WHEN 1 > 2 THEN 3
    ELSE 4
  END AS "ELSE default";

SELECT '6' AS "One",
  CASE
    WHEN 1 > 2 THEN 3
    WHEN 4 < 5 THEN 6
    ELSE 7
  END AS "Two WHEN with default";


SELECT '7' AS "None",
   CASE WHEN random() < 0 THEN 1
   END AS "NULL on no matches";

-- Constant-expression folding shouldn't evaluate unreachable subexpressions
SELECT CASE WHEN 1=0 THEN 1/0 WHEN 1=1 THEN 1 ELSE 2/0 END;
SELECT CASE 1 WHEN 0 THEN 1/0 WHEN 1 THEN 1 ELSE 2/0 END;

-- However we do not currently suppress folding of potentially
-- reachable subexpressions
SELECT CASE WHEN i > 100 THEN 1/0 ELSE 0 END FROM case_tbl;

-- Test for cases involving untyped literals in test expression
SELECT CASE 'a' WHEN 'a' THEN 1 ELSE 2 END;

--
-- Examples of targets involving tables
--

SELECT
  CASE
    WHEN i >= 3 THEN i
  END AS ">= 3 or Null"
  FROM CASE_TBL;

SELECT
  CASE WHEN i >= 3 THEN (i + i)
       ELSE i
  END AS "Simplest Math"
  FROM CASE_TBL;

SELECT i AS "Value",
  CASE WHEN (i < 0) THEN 'small'
       WHEN (i = 0) THEN 'zero'
       WHEN (i = 1) THEN 'one'
       WHEN (i = 2) THEN 'two'
       ELSE 'big'
  END AS "Category"
  FROM CASE_TBL;

SELECT
  CASE WHEN ((i < 0) or (i < 0)) THEN 'small'
       WHEN ((i = 0) or (i = 0)) THEN 'zero'
       WHEN ((i = 1) or (i = 1)) THEN 'one'
       WHEN ((i = 2) or (i = 2)) THEN 'two'
       ELSE 'big'
  END AS "Category"
  FROM CASE_TBL;

--
-- Examples of qualifications involving tables
--

--
-- NULLIF() and COALESCE()
-- Shorthand forms for typical CASE constructs
--  defined in the SQL standard.
--

SELECT * FROM CASE_TBL WHERE COALESCE(f,i) = 4;

SELECT * FROM CASE_TBL WHERE NULLIF(f,i) = 2;

SELECT COALESCE(a.f, b.i, b.j)
  FROM CASE_TBL a, CASE2_TBL b;

SELECT *
  FROM CASE_TBL a, CASE2_TBL b
  WHERE COALESCE(a.f, b.i, b.j) = 2;

SELECT NULLIF(a.i,b.i) AS "NULLIF(a.i,b.i)",
  NULLIF(b.i, 4) AS "NULLIF(b.i,4)"
  FROM CASE_TBL a, CASE2_TBL b;

SELECT *
  FROM CASE_TBL a, CASE2_TBL b
  WHERE COALESCE(f,b.i) = 2;

-- Tests for constant subexpression simplification

explain (costs off)
SELECT * FROM CASE_TBL WHERE NULLIF(1, 2) = 2;

explain (costs off)
SELECT * FROM CASE_TBL WHERE NULLIF(1, 1) IS NOT NULL;

explain (costs off)
SELECT * FROM CASE_TBL WHERE NULLIF(1, null) = 2;

--
-- Examples of updates involving tables
--

UPDATE CASE_TBL
  SET i = CASE WHEN i >= 3 THEN (- i)
                ELSE (2 * i) END;

SELECT * FROM CASE_TBL;

UPDATE CASE_TBL
  SET i = CASE WHEN i >= 2 THEN (2 * i)
                ELSE (3 * i) END;

SELECT * FROM CASE_TBL;

UPDATE CASE_TBL
  SET i = CASE WHEN b.i >= 2 THEN (2 * j)
                ELSE (3 * j) END
  FROM CASE2_TBL b
  WHERE j = -CASE_TBL.i;

SELECT * FROM CASE_TBL;

--
-- Nested CASE expressions
--

-- This test exercises a bug caused by aliasing econtext->caseValue_isNull
-- with the isNull argument of the inner CASE's CaseExpr evaluation.  After
-- evaluating the vol(null) expression in the inner CASE's second WHEN-clause,
-- the isNull flag for the case test value incorrectly became true, causing
-- the third WHEN-clause not to match.  The volatile function calls are needed
-- to prevent constant-folding in the planner, which would hide the bug.

-- Wrap this in a single transaction so the transient '=' operator doesn't
-- cause problems in concurrent sessions
BEGIN;

CREATE FUNCTION vol(text) returns text as
  'begin return $1; end' language plpgsql volatile;

SELECT CASE
  (CASE vol('bar')
    WHEN 'foo' THEN 'it was foo!'
    WHEN vol(null) THEN 'null input'
    WHEN 'bar' THEN 'it was bar!' END
  )
  WHEN 'it was foo!' THEN 'foo recognized'
  WHEN 'it was bar!' THEN 'bar recognized'
  ELSE 'unrecognized' END;

-- In this case, we can't inline the SQL function without confusing things.
CREATE DOMAIN foodomain AS text;

CREATE FUNCTION volfoo(text) returns foodomain as
  'begin return $1::foodomain; end' language plpgsql volatile;

CREATE FUNCTION inline_eq(foodomain, foodomain) returns boolean as
  'SELECT CASE $2::text WHEN $1::text THEN true ELSE false END' language sql;

CREATE OPERATOR = (procedure = inline_eq,
                   leftarg = foodomain, rightarg = foodomain);

SELECT CASE volfoo('bar') WHEN 'foo'::foodomain THEN 'is foo' ELSE 'is not foo' END;

ROLLBACK;

-- Test multiple evaluation of a CASE arg that is a read/write object (#14472)
-- Wrap this in a single transaction so the transient '=' operator doesn't
-- cause problems in concurrent sessions
BEGIN;

CREATE DOMAIN arrdomain AS int[];

CREATE FUNCTION make_ad(int,int) returns arrdomain as
  'declare x arrdomain;
   begin
     x := array[$1,$2];
     return x;
   end' language plpgsql volatile;

CREATE FUNCTION ad_eq(arrdomain, arrdomain) returns boolean as
  'begin return array_eq($1, $2); end' language plpgsql;

CREATE OPERATOR = (procedure = ad_eq,
                   leftarg = arrdomain, rightarg = arrdomain);

SELECT CASE make_ad(1,2)
  WHEN array[2,4]::arrdomain THEN 'wrong'
  WHEN array[2,5]::arrdomain THEN 'still wrong'
  WHEN array[1,2]::arrdomain THEN 'right'
  END;

-- While we're here, also test handling of a NULLIF arg that is a read/write
-- object (bug #18722)

SELECT NULLIF(make_ad(1,2), array[2,3]::arrdomain);

ROLLBACK;

-- Test interaction of CASE with ArrayCoerceExpr (bug #15471)
BEGIN;

CREATE TYPE casetestenum AS ENUM ('e', 'f', 'g');

SELECT
  CASE 'foo'::text
    WHEN 'foo' THEN ARRAY['a', 'b', 'c', 'd'] || enum_range(NULL::casetestenum)::text[]
    ELSE ARRAY['x', 'y']
    END;

ROLLBACK;

--
-- Clean up
--

DROP TABLE CASE_TBL;
DROP TABLE CASE2_TBL;