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There are two implementation techniques: the executor understands a new JOIN_IN jointype, which emits at most one matching row per left-hand row, or the result of the IN's sub-select can be fed through a DISTINCT filter and then joined as an ordinary relation. Along the way, some minor code cleanup in the optimizer; notably, break out most of the jointree-rearrangement preprocessing in planner.c and put it in a new file prep/prepjointree.c.
168 lines
4.6 KiB
Plaintext
168 lines
4.6 KiB
Plaintext
--
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-- SUBSELECT
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--
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SELECT 1 AS one WHERE 1 IN (SELECT 1);
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one
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-----
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1
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(1 row)
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SELECT 1 AS zero WHERE 1 NOT IN (SELECT 1);
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zero
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------
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(0 rows)
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SELECT 1 AS zero WHERE 1 IN (SELECT 2);
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zero
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------
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(0 rows)
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-- Set up some simple test tables
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CREATE TABLE SUBSELECT_TBL (
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f1 integer,
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f2 integer,
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f3 float
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);
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INSERT INTO SUBSELECT_TBL VALUES (1, 2, 3);
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INSERT INTO SUBSELECT_TBL VALUES (2, 3, 4);
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INSERT INTO SUBSELECT_TBL VALUES (3, 4, 5);
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INSERT INTO SUBSELECT_TBL VALUES (1, 1, 1);
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INSERT INTO SUBSELECT_TBL VALUES (2, 2, 2);
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INSERT INTO SUBSELECT_TBL VALUES (3, 3, 3);
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INSERT INTO SUBSELECT_TBL VALUES (6, 7, 8);
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INSERT INTO SUBSELECT_TBL VALUES (8, 9, NULL);
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SELECT '' AS eight, * FROM SUBSELECT_TBL;
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eight | f1 | f2 | f3
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-------+----+----+----
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| 1 | 2 | 3
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| 2 | 3 | 4
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| 3 | 4 | 5
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| 1 | 1 | 1
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| 2 | 2 | 2
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| 3 | 3 | 3
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| 6 | 7 | 8
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| 8 | 9 |
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(8 rows)
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-- Uncorrelated subselects
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SELECT '' AS two, f1 AS "Constant Select" FROM SUBSELECT_TBL
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WHERE f1 IN (SELECT 1);
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two | Constant Select
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-----+-----------------
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| 1
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| 1
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(2 rows)
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SELECT '' AS six, f1 AS "Uncorrelated Field" FROM SUBSELECT_TBL
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WHERE f1 IN (SELECT f2 FROM SUBSELECT_TBL);
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six | Uncorrelated Field
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-----+--------------------
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| 1
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| 1
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| 2
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| 2
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| 3
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| 3
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(6 rows)
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SELECT '' AS six, f1 AS "Uncorrelated Field" FROM SUBSELECT_TBL
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WHERE f1 IN (SELECT f2 FROM SUBSELECT_TBL WHERE
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f2 IN (SELECT f1 FROM SUBSELECT_TBL));
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six | Uncorrelated Field
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-----+--------------------
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| 1
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| 1
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| 2
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| 2
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| 3
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| 3
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(6 rows)
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SELECT '' AS three, f1, f2
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FROM SUBSELECT_TBL
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WHERE (f1, f2) NOT IN (SELECT f2, CAST(f3 AS int4) FROM SUBSELECT_TBL
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WHERE f3 IS NOT NULL);
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three | f1 | f2
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-------+----+----
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| 1 | 2
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| 6 | 7
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| 8 | 9
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(3 rows)
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-- Correlated subselects
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SELECT '' AS six, f1 AS "Correlated Field", f2 AS "Second Field"
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FROM SUBSELECT_TBL upper
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WHERE f1 IN (SELECT f2 FROM SUBSELECT_TBL WHERE f1 = upper.f1);
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six | Correlated Field | Second Field
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-----+------------------+--------------
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| 1 | 2
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| 2 | 3
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| 3 | 4
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| 1 | 1
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| 2 | 2
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| 3 | 3
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(6 rows)
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SELECT '' AS six, f1 AS "Correlated Field", f3 AS "Second Field"
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FROM SUBSELECT_TBL upper
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WHERE f1 IN
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(SELECT f2 FROM SUBSELECT_TBL WHERE CAST(upper.f2 AS float) = f3);
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six | Correlated Field | Second Field
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-----+------------------+--------------
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| 2 | 4
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| 3 | 5
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| 1 | 1
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| 2 | 2
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| 3 | 3
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(5 rows)
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SELECT '' AS six, f1 AS "Correlated Field", f3 AS "Second Field"
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FROM SUBSELECT_TBL upper
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WHERE f3 IN (SELECT upper.f1 + f2 FROM SUBSELECT_TBL
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WHERE f2 = CAST(f3 AS integer));
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six | Correlated Field | Second Field
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-----+------------------+--------------
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| 1 | 3
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| 2 | 4
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| 3 | 5
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| 6 | 8
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(4 rows)
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SELECT '' AS five, f1 AS "Correlated Field"
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FROM SUBSELECT_TBL
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WHERE (f1, f2) IN (SELECT f2, CAST(f3 AS int4) FROM SUBSELECT_TBL
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WHERE f3 IS NOT NULL);
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five | Correlated Field
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------+------------------
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| 1
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| 2
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| 2
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| 3
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| 3
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(5 rows)
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--
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-- Use some existing tables in the regression test
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--
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SELECT '' AS eight, ss.f1 AS "Correlated Field", ss.f3 AS "Second Field"
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FROM SUBSELECT_TBL ss
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WHERE f1 NOT IN (SELECT f1+1 FROM INT4_TBL WHERE f1 != ss.f1);
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eight | Correlated Field | Second Field
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-------+------------------+--------------
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| 2 | 4
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| 3 | 5
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| 2 | 2
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| 3 | 3
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| 6 | 8
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| 8 |
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(6 rows)
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select q1, float8(count(*)) / (select count(*) from int8_tbl)
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from int8_tbl group by q1 order by q1;
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q1 | ?column?
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------------------+----------
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123 | 0.4
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4567890123456789 | 0.6
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(2 rows)
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