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Allow COPY FROM to filter data using WHERE conditions

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Extends the COPY FROM command with a WHERE condition, which allows doing
various types of filtering while importing the data (random sampling,
condition on a data column, etc.).  Until now such filtering required
either preprocessing of the input data, or importing all data and then
filtering in the database. COPY FROM ... WHERE is an easy-to-use and
low-overhead alternative for most simple cases.

Author: Surafel Temesgen
Reviewed-by: Tomas Vondra, Masahiko Sawada, Lim Myungkyu
Discussion: https://www.postgresql.org/message-id/flat/CALAY4q_DdpWDuB5-Zyi-oTtO2uSk8pmy+dupiRe3AvAc++1imA@mail.gmail.com
This commit is contained in:
Tomas Vondra
2019-01-19 23:48:16 +01:00
parent d6ef7fe75c
commit 31f3817402
13 changed files with 175 additions and 4 deletions
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40
src/test/regress/expected/copy2.out
View File

@ -49,6 +49,32 @@ CONTEXT: COPY x, line 1: "2002 232 40 50 60 70 80"
COPY x (b, c, d, e) from stdin delimiter ',' null 'x';
COPY x from stdin WITH DELIMITER AS ';' NULL AS '';
COPY x from stdin WITH DELIMITER AS ':' NULL AS E'\\X' ENCODING 'sql_ascii';
COPY x TO stdout WHERE a = 1;
ERROR: WHERE clause not allowed with COPY TO
LINE 1: COPY x TO stdout WHERE a = 1;
^
COPY x from stdin WHERE a = 50004;
COPY x from stdin WHERE a > 60003;
COPY x from stdin WHERE f > 60003;
ERROR: column "f" does not exist
LINE 1: COPY x from stdin WHERE f > 60003;
^
COPY x from stdin WHERE a = max(x.b);
ERROR: aggregate functions are not allowed in COPY FROM WHERE conditions
LINE 1: COPY x from stdin WHERE a = max(x.b);
^
COPY x from stdin WHERE a IN (SELECT 1 FROM x);
ERROR: cannot use subquery in COPY FROM WHERE condition
LINE 1: COPY x from stdin WHERE a IN (SELECT 1 FROM x);
^
COPY x from stdin WHERE a IN (generate_series(1,5));
ERROR: set-returning functions are not allowed in COPY FROM WHERE conditions
LINE 1: COPY x from stdin WHERE a IN (generate_series(1,5));
^
COPY x from stdin WHERE a = row_number() over(b);
ERROR: window functions are not allowed in COPY FROM WHERE conditions
LINE 1: COPY x from stdin WHERE a = row_number() over(b);
^
-- check results of copy in
SELECT * FROM x;
a | b | c | d | e
@ -73,12 +99,15 @@ SELECT * FROM x;
4006 | 6 | BackslashN | \N | before trigger fired
4007 | 7 | XX | XX | before trigger fired
4008 | 8 | Delimiter | : | before trigger fired
50004 | 25 | 35 | 45 | before trigger fired
60004 | 25 | 35 | 45 | before trigger fired
60005 | 26 | 36 | 46 | before trigger fired
1 | 1 | stuff | test_1 | after trigger fired
2 | 2 | stuff | test_2 | after trigger fired
3 | 3 | stuff | test_3 | after trigger fired
4 | 4 | stuff | test_4 | after trigger fired
5 | 5 | stuff | test_5 | after trigger fired
(25 rows)
(28 rows)
-- check copy out
COPY x TO stdout;
@ -102,6 +131,9 @@ COPY x TO stdout;
4006 6 BackslashN \\N before trigger fired
4007 7 XX XX before trigger fired
4008 8 Delimiter : before trigger fired
50004 25 35 45 before trigger fired
60004 25 35 45 before trigger fired
60005 26 36 46 before trigger fired
1 1 stuff test_1 after trigger fired
2 2 stuff test_2 after trigger fired
3 3 stuff test_3 after trigger fired
@ -128,6 +160,9 @@ N before trigger fired
BackslashN before trigger fired
XX before trigger fired
Delimiter before trigger fired
35 before trigger fired
35 before trigger fired
36 before trigger fired
stuff after trigger fired
stuff after trigger fired
stuff after trigger fired
@ -154,6 +189,9 @@ I'm null before trigger fired
6 before trigger fired
7 before trigger fired
8 before trigger fired
25 before trigger fired
25 before trigger fired
26 before trigger fired
1 after trigger fired
2 after trigger fired
3 after trigger fired

26
src/test/regress/sql/copy2.sql
View File

@ -95,6 +95,32 @@ COPY x from stdin WITH DELIMITER AS ':' NULL AS E'\\X' ENCODING 'sql_ascii';
4008:8:Delimiter:\::\:
\.
COPY x TO stdout WHERE a = 1;
COPY x from stdin WHERE a = 50004;
50003 24 34 44 54
50004 25 35 45 55
50005 26 36 46 56
\.
COPY x from stdin WHERE a > 60003;
60001 22 32 42 52
60002 23 33 43 53
60003 24 34 44 54
60004 25 35 45 55
60005 26 36 46 56
\.
COPY x from stdin WHERE f > 60003;
COPY x from stdin WHERE a = max(x.b);
COPY x from stdin WHERE a IN (SELECT 1 FROM x);
COPY x from stdin WHERE a IN (generate_series(1,5));
COPY x from stdin WHERE a = row_number() over(b);
-- check results of copy in
SELECT * FROM x;