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Add IGNORE NULLS/RESPECT NULLS option to Window functions.
Add IGNORE NULLS/RESPECT NULLS option (null treatment clause) to lead, lag, first_value, last_value and nth_value window functions. If unspecified, the default is RESPECT NULLS which includes NULL values in any result calculation. IGNORE NULLS ignores NULL values. Built-in window functions are modified to call new API WinCheckAndInitializeNullTreatment() to indicate whether they accept IGNORE NULLS/RESPECT NULLS option or not (the API can be called by user defined window functions as well). If WinGetFuncArgInPartition's allowNullTreatment argument is true and IGNORE NULLS option is given, WinGetFuncArgInPartition() or WinGetFuncArgInFrame() will return evaluated function's argument expression on specified non NULL row (if it exists) in the partition or the frame. When IGNORE NULLS option is given, window functions need to visit and evaluate same rows over and over again to look for non null rows. To mitigate the issue, 2-bit not null information array is created while executing window functions to remember whether the row has been already evaluated to NULL or NOT NULL. If already evaluated, we could skip the evaluation work, thus we could get better performance. Author: Oliver Ford <ojford@gmail.com> Co-authored-by: Tatsuo Ishii <ishii@postgresql.org> Reviewed-by: Krasiyan Andreev <krasiyan@gmail.com> Reviewed-by: Andrew Gierth <andrew@tao11.riddles.org.uk> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Reviewed-by: David Fetter <david@fetter.org> Reviewed-by: Vik Fearing <vik@postgresfriends.org> Reviewed-by: "David G. Johnston" <david.g.johnston@gmail.com> Reviewed-by: Chao Li <lic@highgo.com> Discussion: https://postgr.es/m/flat/CAGMVOdsbtRwE_4+v8zjH1d9xfovDeQAGLkP_B6k69_VoFEgX-A@mail.gmail.com
This commit is contained in:
Tatsuo Ishii
@@ -5453,3 +5453,409 @@ SELECT * FROM pg_temp.f(2);
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{5}
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(5 rows)
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-- IGNORE NULLS tests
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CREATE TEMPORARY TABLE planets (
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name text,
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distance text,
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orbit integer
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);
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INSERT INTO planets VALUES
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('mercury', 'close', 88),
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('venus', 'close', 224),
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('earth', 'close', NULL),
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('mars', 'close', NULL),
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('jupiter', 'close', 4332),
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('saturn', 'far', 24491),
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('uranus', 'far', NULL),
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('neptune', 'far', 60182),
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('pluto', 'far', 90560),
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('xyzzy', 'far', NULL);
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-- test ruleutils
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CREATE VIEW planets_view AS
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SELECT name,
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orbit,
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lag(orbit) OVER w AS lag,
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lag(orbit) RESPECT NULLS OVER w AS lag_respect,
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lag(orbit) IGNORE NULLS OVER w AS lag_ignore
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FROM planets
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WINDOW w AS (ORDER BY name)
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;
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NOTICE: view "planets_view" will be a temporary view
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SELECT pg_get_viewdef('planets_view');
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pg_get_viewdef
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--------------------------------------------------
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SELECT name, +
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orbit, +
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lag(orbit) OVER w AS lag, +
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lag(orbit) OVER w AS lag_respect, +
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lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
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FROM planets +
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WINDOW w AS (ORDER BY name);
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(1 row)
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-- lag
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SELECT name,
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orbit,
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lag(orbit) OVER w AS lag,
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lag(orbit) RESPECT NULLS OVER w AS lag_respect,
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lag(orbit) IGNORE NULLS OVER w AS lag_ignore
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FROM planets
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WINDOW w AS (ORDER BY name)
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;
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name | orbit | lag | lag_respect | lag_ignore
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---------+-------+-------+-------------+------------
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earth | | | |
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jupiter | 4332 | | |
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mars | | 4332 | 4332 | 4332
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mercury | 88 | | | 4332
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neptune | 60182 | 88 | 88 | 88
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pluto | 90560 | 60182 | 60182 | 60182
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saturn | 24491 | 90560 | 90560 | 90560
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uranus | | 24491 | 24491 | 24491
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venus | 224 | | | 24491
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xyzzy | | 224 | 224 | 224
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(10 rows)
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-- lead
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SELECT name,
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orbit,
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lead(orbit) OVER w AS lead,
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lead(orbit) RESPECT NULLS OVER w AS lead_respect,
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lead(orbit) IGNORE NULLS OVER w AS lead_ignore
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FROM planets
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WINDOW w AS (ORDER BY name)
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;
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name | orbit | lead | lead_respect | lead_ignore
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---------+-------+-------+--------------+-------------
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earth | | 4332 | 4332 | 4332
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jupiter | 4332 | | | 88
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mars | | 88 | 88 | 88
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mercury | 88 | 60182 | 60182 | 60182
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neptune | 60182 | 90560 | 90560 | 90560
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pluto | 90560 | 24491 | 24491 | 24491
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saturn | 24491 | | | 224
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uranus | | 224 | 224 | 224
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venus | 224 | | |
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xyzzy | | | |
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(10 rows)
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-- first_value
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SELECT name,
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orbit,
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first_value(orbit) RESPECT NULLS OVER w1,
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first_value(orbit) IGNORE NULLS OVER w1,
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first_value(orbit) RESPECT NULLS OVER w2,
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first_value(orbit) IGNORE NULLS OVER w2
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FROM planets
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WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
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w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
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;
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name | orbit | first_value | first_value | first_value | first_value
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---------+-------+-------------+-------------+-------------+-------------
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earth | | | 4332 | | 4332
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jupiter | 4332 | | 4332 | | 4332
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mars | | | 4332 | | 4332
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mercury | 88 | | 4332 | 4332 | 4332
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neptune | 60182 | | 4332 | | 88
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pluto | 90560 | | 4332 | 88 | 88
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saturn | 24491 | | 4332 | 60182 | 60182
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uranus | | | 4332 | 90560 | 90560
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venus | 224 | | 4332 | 24491 | 24491
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xyzzy | | | 4332 | | 224
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(10 rows)
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-- nth_value
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SELECT name,
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orbit,
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nth_value(orbit, 2) RESPECT NULLS OVER w1,
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nth_value(orbit, 2) IGNORE NULLS OVER w1,
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nth_value(orbit, 2) RESPECT NULLS OVER w2,
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nth_value(orbit, 2) IGNORE NULLS OVER w2
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FROM planets
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WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
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w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
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;
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name | orbit | nth_value | nth_value | nth_value | nth_value
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---------+-------+-----------+-----------+-----------+-----------
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earth | | 4332 | 88 | 4332 |
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jupiter | 4332 | 4332 | 88 | 4332 | 88
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mars | | 4332 | 88 | 4332 | 88
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mercury | 88 | 4332 | 88 | | 88
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neptune | 60182 | 4332 | 88 | 88 | 60182
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pluto | 90560 | 4332 | 88 | 60182 | 60182
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saturn | 24491 | 4332 | 88 | 90560 | 90560
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uranus | | 4332 | 88 | 24491 | 24491
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venus | 224 | 4332 | 88 | | 224
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xyzzy | | 4332 | 88 | 224 |
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(10 rows)
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-- last_value
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SELECT name,
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orbit,
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last_value(orbit) RESPECT NULLS OVER w1,
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last_value(orbit) IGNORE NULLS OVER w1,
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last_value(orbit) RESPECT NULLS OVER w2,
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last_value(orbit) IGNORE NULLS OVER w2
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FROM planets
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WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
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w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
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;
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name | orbit | last_value | last_value | last_value | last_value
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---------+-------+------------+------------+------------+------------
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earth | | | 224 | | 4332
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jupiter | 4332 | | 224 | 88 | 88
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mars | | | 224 | 60182 | 60182
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mercury | 88 | | 224 | 90560 | 90560
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neptune | 60182 | | 224 | 24491 | 24491
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pluto | 90560 | | 224 | | 24491
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saturn | 24491 | | 224 | 224 | 224
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uranus | | | 224 | | 224
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venus | 224 | | 224 | | 224
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xyzzy | | | 224 | | 224
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(10 rows)
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-- exclude current row
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SELECT name,
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orbit,
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first_value(orbit) IGNORE NULLS OVER w,
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last_value(orbit) IGNORE NULLS OVER w,
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nth_value(orbit, 2) IGNORE NULLS OVER w,
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lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
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lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
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FROM planets
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WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
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;
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name | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore
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---------+-------+-------------+------------+-----------+-------------+------------
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earth | | 4332 | 4332 | | 4332 |
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jupiter | 4332 | 88 | 88 | | 88 |
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mars | | 4332 | 60182 | 88 | 88 | 4332
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mercury | 88 | 4332 | 90560 | 60182 | 60182 | 4332
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neptune | 60182 | 88 | 24491 | 90560 | 90560 | 88
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pluto | 90560 | 88 | 24491 | 60182 | 24491 | 60182
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saturn | 24491 | 60182 | 224 | 90560 | 224 | 90560
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uranus | | 90560 | 224 | 24491 | 224 | 24491
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venus | 224 | 24491 | 24491 | | | 24491
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xyzzy | | 224 | 224 | | | 224
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(10 rows)
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-- valid and invalid functions
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SELECT sum(orbit) OVER () FROM planets; -- succeeds
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sum
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--------
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179877
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179877
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179877
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179877
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179877
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179877
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179877
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179877
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179877
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179877
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(10 rows)
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SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
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ERROR: aggregate functions do not accept RESPECT/IGNORE NULLS
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LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
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^
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SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
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ERROR: aggregate functions do not accept RESPECT/IGNORE NULLS
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LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
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^
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SELECT row_number() OVER () FROM planets; -- succeeds
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row_number
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------------
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1
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2
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3
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4
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5
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6
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7
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8
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9
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10
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(10 rows)
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SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
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ERROR: function row_number does not allow RESPECT/IGNORE NULLS
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SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
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ERROR: function row_number does not allow RESPECT/IGNORE NULLS
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SELECT rank() OVER () FROM planets; -- succeeds
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rank
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------
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1
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1
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1
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1
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1
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1
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1
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1
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1
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1
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(10 rows)
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SELECT rank() RESPECT NULLS OVER () FROM planets; -- fails
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ERROR: function rank does not allow RESPECT/IGNORE NULLS
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SELECT rank() IGNORE NULLS OVER () FROM planets; -- fails
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ERROR: function rank does not allow RESPECT/IGNORE NULLS
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SELECT dense_rank() OVER () FROM planets; -- succeeds
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dense_rank
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------------
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1
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1
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1
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1
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1
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1
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1
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1
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1
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1
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(10 rows)
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SELECT dense_rank() RESPECT NULLS OVER () FROM planets; -- fails
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ERROR: function dense_rank does not allow RESPECT/IGNORE NULLS
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SELECT dense_rank() IGNORE NULLS OVER () FROM planets; -- fails
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ERROR: function dense_rank does not allow RESPECT/IGNORE NULLS
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SELECT percent_rank() OVER () FROM planets; -- succeeds
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percent_rank
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--------------
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0
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0
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0
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0
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0
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0
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0
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0
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0
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0
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(10 rows)
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SELECT percent_rank() RESPECT NULLS OVER () FROM planets; -- fails
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ERROR: function percent_rank does not allow RESPECT/IGNORE NULLS
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SELECT percent_rank() IGNORE NULLS OVER () FROM planets; -- fails
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ERROR: function percent_rank does not allow RESPECT/IGNORE NULLS
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SELECT cume_dist() OVER () FROM planets; -- succeeds
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cume_dist
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-----------
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1
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1
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1
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1
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1
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1
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1
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1
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1
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1
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(10 rows)
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SELECT cume_dist() RESPECT NULLS OVER () FROM planets; -- fails
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ERROR: function cume_dist does not allow RESPECT/IGNORE NULLS
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SELECT cume_dist() IGNORE NULLS OVER () FROM planets; -- fails
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ERROR: function cume_dist does not allow RESPECT/IGNORE NULLS
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SELECT ntile(1) OVER () FROM planets; -- succeeds
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ntile
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-------
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1
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1
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1
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1
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1
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1
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1
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1
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1
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1
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(10 rows)
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SELECT ntile(1) RESPECT NULLS OVER () FROM planets; -- fails
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ERROR: function ntile does not allow RESPECT/IGNORE NULLS
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SELECT ntile(1) IGNORE NULLS OVER () FROM planets; -- fails
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ERROR: function ntile does not allow RESPECT/IGNORE NULLS
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-- test two consecutive nulls
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update planets set orbit=null where name='jupiter';
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SELECT name,
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orbit,
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first_value(orbit) IGNORE NULLS OVER w,
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last_value(orbit) IGNORE NULLS OVER w,
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nth_value(orbit, 2) IGNORE NULLS OVER w,
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lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
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lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
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FROM planets
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WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
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;
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name | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore
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---------+-------+-------------+------------+-----------+-------------+------------
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earth | | | | | 88 |
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jupiter | | 88 | 88 | | 88 |
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mars | | 88 | 60182 | 60182 | 88 |
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mercury | 88 | 88 | 90560 | 60182 | 60182 |
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neptune | 60182 | 88 | 24491 | 60182 | 90560 | 88
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pluto | 90560 | 88 | 24491 | 60182 | 24491 | 60182
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saturn | 24491 | 60182 | 224 | 90560 | 224 | 90560
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uranus | | 90560 | 224 | 24491 | 224 | 24491
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venus | 224 | 24491 | 224 | 224 | | 24491
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xyzzy | | 224 | 224 | | | 224
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(10 rows)
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-- test partitions
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SELECT name,
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distance,
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orbit,
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first_value(orbit) IGNORE NULLS OVER w,
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last_value(orbit) IGNORE NULLS OVER w,
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nth_value(orbit, 2) IGNORE NULLS OVER w,
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lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
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lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
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FROM planets
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WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
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;
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name | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore
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---------+----------+-------+-------------+------------+-----------+-------------+------------
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earth | close | | | | | 88 |
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jupiter | close | | 88 | 88 | | 88 |
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mars | close | | 88 | 224 | 224 | 88 |
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mercury | close | 88 | 88 | 224 | 224 | 224 |
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venus | close | 224 | 88 | 224 | 224 | | 88
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neptune | far | 60182 | 60182 | 24491 | 90560 | 90560 |
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pluto | far | 90560 | 60182 | 24491 | 90560 | 24491 | 60182
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saturn | far | 24491 | 60182 | 24491 | 90560 | | 90560
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uranus | far | | 90560 | 24491 | 24491 | | 24491
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xyzzy | far | | 24491 | 24491 | | | 24491
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(10 rows)
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-- nth_value without nulls
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SELECT x,
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nth_value(x,2) IGNORE NULLS OVER w
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FROM generate_series(1,5) g(x)
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WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
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x | nth_value
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---+-----------
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1 | 3
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2 | 3
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3 | 2
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4 | 3
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5 | 4
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(5 rows)
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SELECT x,
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nth_value(x,2) IGNORE NULLS OVER w
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FROM generate_series(1,5) g(x)
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WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
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x | nth_value
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---+-----------
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1 | 2
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2 | 2
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3 | 2
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4 | 3
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5 | 4
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(5 rows)
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--cleanup
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DROP TABLE planets CASCADE;
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NOTICE: drop cascades to view planets_view
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@@ -1958,3 +1958,165 @@ $$ LANGUAGE SQL STABLE;
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|
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EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
|
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SELECT * FROM pg_temp.f(2);
|
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|
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-- IGNORE NULLS tests
|
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|
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CREATE TEMPORARY TABLE planets (
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name text,
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distance text,
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orbit integer
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||||
);
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INSERT INTO planets VALUES
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('mercury', 'close', 88),
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('venus', 'close', 224),
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('earth', 'close', NULL),
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('mars', 'close', NULL),
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('jupiter', 'close', 4332),
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('saturn', 'far', 24491),
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('uranus', 'far', NULL),
|
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('neptune', 'far', 60182),
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('pluto', 'far', 90560),
|
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('xyzzy', 'far', NULL);
|
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|
||||
-- test ruleutils
|
||||
CREATE VIEW planets_view AS
|
||||
SELECT name,
|
||||
orbit,
|
||||
lag(orbit) OVER w AS lag,
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lag(orbit) RESPECT NULLS OVER w AS lag_respect,
|
||||
lag(orbit) IGNORE NULLS OVER w AS lag_ignore
|
||||
FROM planets
|
||||
WINDOW w AS (ORDER BY name)
|
||||
;
|
||||
SELECT pg_get_viewdef('planets_view');
|
||||
|
||||
-- lag
|
||||
SELECT name,
|
||||
orbit,
|
||||
lag(orbit) OVER w AS lag,
|
||||
lag(orbit) RESPECT NULLS OVER w AS lag_respect,
|
||||
lag(orbit) IGNORE NULLS OVER w AS lag_ignore
|
||||
FROM planets
|
||||
WINDOW w AS (ORDER BY name)
|
||||
;
|
||||
|
||||
-- lead
|
||||
SELECT name,
|
||||
orbit,
|
||||
lead(orbit) OVER w AS lead,
|
||||
lead(orbit) RESPECT NULLS OVER w AS lead_respect,
|
||||
lead(orbit) IGNORE NULLS OVER w AS lead_ignore
|
||||
FROM planets
|
||||
WINDOW w AS (ORDER BY name)
|
||||
;
|
||||
|
||||
-- first_value
|
||||
SELECT name,
|
||||
orbit,
|
||||
first_value(orbit) RESPECT NULLS OVER w1,
|
||||
first_value(orbit) IGNORE NULLS OVER w1,
|
||||
first_value(orbit) RESPECT NULLS OVER w2,
|
||||
first_value(orbit) IGNORE NULLS OVER w2
|
||||
FROM planets
|
||||
WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
|
||||
w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
|
||||
;
|
||||
|
||||
-- nth_value
|
||||
SELECT name,
|
||||
orbit,
|
||||
nth_value(orbit, 2) RESPECT NULLS OVER w1,
|
||||
nth_value(orbit, 2) IGNORE NULLS OVER w1,
|
||||
nth_value(orbit, 2) RESPECT NULLS OVER w2,
|
||||
nth_value(orbit, 2) IGNORE NULLS OVER w2
|
||||
FROM planets
|
||||
WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
|
||||
w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
|
||||
;
|
||||
|
||||
-- last_value
|
||||
SELECT name,
|
||||
orbit,
|
||||
last_value(orbit) RESPECT NULLS OVER w1,
|
||||
last_value(orbit) IGNORE NULLS OVER w1,
|
||||
last_value(orbit) RESPECT NULLS OVER w2,
|
||||
last_value(orbit) IGNORE NULLS OVER w2
|
||||
FROM planets
|
||||
WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
|
||||
w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
|
||||
;
|
||||
|
||||
-- exclude current row
|
||||
SELECT name,
|
||||
orbit,
|
||||
first_value(orbit) IGNORE NULLS OVER w,
|
||||
last_value(orbit) IGNORE NULLS OVER w,
|
||||
nth_value(orbit, 2) IGNORE NULLS OVER w,
|
||||
lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
|
||||
lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
|
||||
FROM planets
|
||||
WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
|
||||
;
|
||||
|
||||
-- valid and invalid functions
|
||||
SELECT sum(orbit) OVER () FROM planets; -- succeeds
|
||||
SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
|
||||
SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
|
||||
SELECT row_number() OVER () FROM planets; -- succeeds
|
||||
SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
|
||||
SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
|
||||
SELECT rank() OVER () FROM planets; -- succeeds
|
||||
SELECT rank() RESPECT NULLS OVER () FROM planets; -- fails
|
||||
SELECT rank() IGNORE NULLS OVER () FROM planets; -- fails
|
||||
SELECT dense_rank() OVER () FROM planets; -- succeeds
|
||||
SELECT dense_rank() RESPECT NULLS OVER () FROM planets; -- fails
|
||||
SELECT dense_rank() IGNORE NULLS OVER () FROM planets; -- fails
|
||||
SELECT percent_rank() OVER () FROM planets; -- succeeds
|
||||
SELECT percent_rank() RESPECT NULLS OVER () FROM planets; -- fails
|
||||
SELECT percent_rank() IGNORE NULLS OVER () FROM planets; -- fails
|
||||
SELECT cume_dist() OVER () FROM planets; -- succeeds
|
||||
SELECT cume_dist() RESPECT NULLS OVER () FROM planets; -- fails
|
||||
SELECT cume_dist() IGNORE NULLS OVER () FROM planets; -- fails
|
||||
SELECT ntile(1) OVER () FROM planets; -- succeeds
|
||||
SELECT ntile(1) RESPECT NULLS OVER () FROM planets; -- fails
|
||||
SELECT ntile(1) IGNORE NULLS OVER () FROM planets; -- fails
|
||||
|
||||
-- test two consecutive nulls
|
||||
update planets set orbit=null where name='jupiter';
|
||||
SELECT name,
|
||||
orbit,
|
||||
first_value(orbit) IGNORE NULLS OVER w,
|
||||
last_value(orbit) IGNORE NULLS OVER w,
|
||||
nth_value(orbit, 2) IGNORE NULLS OVER w,
|
||||
lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
|
||||
lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
|
||||
FROM planets
|
||||
WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
|
||||
;
|
||||
|
||||
-- test partitions
|
||||
SELECT name,
|
||||
distance,
|
||||
orbit,
|
||||
first_value(orbit) IGNORE NULLS OVER w,
|
||||
last_value(orbit) IGNORE NULLS OVER w,
|
||||
nth_value(orbit, 2) IGNORE NULLS OVER w,
|
||||
lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
|
||||
lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
|
||||
FROM planets
|
||||
WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
|
||||
;
|
||||
|
||||
-- nth_value without nulls
|
||||
SELECT x,
|
||||
nth_value(x,2) IGNORE NULLS OVER w
|
||||
FROM generate_series(1,5) g(x)
|
||||
WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
|
||||
SELECT x,
|
||||
nth_value(x,2) IGNORE NULLS OVER w
|
||||
FROM generate_series(1,5) g(x)
|
||||
WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
|
||||
|
||||
--cleanup
|
||||
DROP TABLE planets CASCADE;
|
||||
|
||||
Reference in New Issue
Block a user