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Commitdc2d9ef

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Doc: fix out-of-date example of SPI usage.
The "count" argument of SPI_exec() only limits execution whenthe query is actually returning rows. This was not the casebefore PG 9.0, so this example was correct when written; butwe missed updating it in commit2ddc600. Extend the exampleto show the behavior both with and without RETURNING.While here, improve the commentary and markup for the restof the example.David G. Johnston and Tom Lane, per report from Curt Kolovson.Back-patch to all supported branches.Discussion:https://postgr.es/m/CANhYJV6HWtgz_qjx_APfK0PAgLUzY-2vjLuj7i_o=TZF1LAQew@mail.gmail.com
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‎doc/src/sgml/spi.sgml

Lines changed: 33 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -4679,15 +4679,16 @@ CREATE FUNCTION execq(text, integer) RETURNS int8
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=> INSERT INTO a VALUES (execq('INSERT INTO a VALUES (0)', 0));
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INSERT 0 1
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=> SELECT execq('SELECT * FROM a', 0);
4682-
INFO: EXECQ: 0 -- inserted by execq
4683-
INFO: EXECQ: 1 -- returned by execq and inserted by upper INSERT
4682+
INFO: EXECQ: 0<lineannotation>-- inserted by execq</lineannotation>
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INFO: EXECQ: 1<lineannotation>-- returned by execq and inserted by upper INSERT</lineannotation>
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execq
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-------
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2
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(1 row)
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4690-
=&gt; SELECT execq('INSERT INTO a SELECT x + 2 FROM a', 1);
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=&gt; SELECT execq('INSERT INTO a SELECT x + 2 FROM a RETURNING *', 1);
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INFO: EXECQ: 2 <lineannotation>-- 0 + 2, then execution was stopped by count</lineannotation>
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execq
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-------
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1
@@ -4696,21 +4697,38 @@ INFO: EXECQ: 1 -- returned by execq and inserted by upper INSERT
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=&gt; SELECT execq('SELECT * FROM a', 10);
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INFO: EXECQ: 0
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INFO: EXECQ: 1
4699-
INFO: EXECQ: 2 -- 0 + 2, only one row inserted - as specified
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INFO: EXECQ: 2
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execq
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-------
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3 <lineannotation>-- 10 is the max value only, 3 is the real number of rows</lineannotation>
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(1 row)
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=&gt; SELECT execq('INSERT INTO a SELECT x + 10 FROM a', 1);
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execq
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-------
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3 --10 is the max value only, 3 is the real number of rows
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3<lineannotation>--all rows processed; count does not stop it, because nothing is returned</lineannotation>
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(1 row)
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4713+
=&gt; SELECT * FROM a;
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x
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----
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0
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1
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2
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10
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11
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12
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(6 rows)
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=&gt; DELETE FROM a;
4707-
DELETE3
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DELETE6
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=&gt; INSERT INTO a VALUES (execq('SELECT * FROM a', 0) + 1);
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INSERT 0 1
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=&gt; SELECT * FROM a;
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x
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---
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1 -- no rows in a (0) + 1
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1<lineannotation>--0 (no rows in a) + 1</lineannotation>
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(1 row)
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=&gt; INSERT INTO a VALUES (execq('SELECT * FROM a', 0) + 1);
@@ -4720,15 +4738,16 @@ INSERT 0 1
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x
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---
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1
4723-
2 -- there was one row in a + 1
4741+
2<lineannotation>--1 (there was one row in a) + 1</lineannotation>
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(2 rows)
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4726-
-- This demonstrates the data changes visibility rule:
4744+
<lineannotation>-- This demonstrates the data changes visibility rule.</lineannotation>
4745+
<lineannotation>-- execq is called twice and sees different numbers of rows each time:</lineannotation>
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=&gt; INSERT INTO a SELECT execq('SELECT * FROM a', 0) * x FROM a;
4729-
INFO: EXECQ: 1
4748+
INFO: EXECQ: 1 <lineannotation>-- results from first execq</lineannotation>
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INFO: EXECQ: 2
4731-
INFO: EXECQ: 1
4750+
INFO: EXECQ: 1 <lineannotation>-- results from second execq</lineannotation>
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INFO: EXECQ: 2
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INFO: EXECQ: 2
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INSERT 0 2
@@ -4737,10 +4756,9 @@ INSERT 0 2
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---
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1
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2
4740-
2 -- 2 rows * 1 (x in first row)
4741-
6 -- 3 rows (2 + 1 just inserted) * 2 (x in second row)
4742-
(4 rows) ^^^^^^
4743-
rows visible to execq() in different invocations
4759+
2 <lineannotation>-- 2 rows * 1 (x in first row)</lineannotation>
4760+
6 <lineannotation>-- 3 rows (2 + 1 just inserted) * 2 (x in second row)</lineannotation>
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(4 rows)
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</programlisting>
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</para>
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</sect1>

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