/*
* tablefunc
*
* Sample to demonstrate C functions which return setof scalar
* and setof composite.
* Joe Conway <mail@joeconway.com>
*
* Copyright 2002 by PostgreSQL Global Development Group
*
* Permission to use, copy, modify, and distribute this software and its
* documentation for any purpose, without fee, and without a written agreement
* is hereby granted, provided that the above copyright notice and this
* paragraph and the following two paragraphs appear in all copies.
*
* IN NO EVENT SHALL THE AUTHORS OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
* LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
* DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* THE AUTHORS AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
* ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
*
*/
Version 0.1 (20 July, 2002):
First release
Release Notes:
Version 0.1
- initial release
Installation:
Place these files in a directory called 'tablefunc' under 'contrib' in the
PostgreSQL source tree. Then run:
make
make install
You can use tablefunc.sql to create the functions in your database of choice, e.g.
psql -U postgres template1 < tablefunc.sql
installs following functions into database template1:
normal_rand(int numvals, float8 mean, float8 stddev, int seed)
- returns a set of normally distributed float8 values
crosstabN(text sql)
- returns a set of row_name plus N category value columns
- crosstab2(), crosstab3(), and crosstab4() are defined for you,
but you can create additional crosstab functions per the instructions
in the documentation below.
crosstab(text sql, N int)
- returns a set of row_name plus N category value columns
- requires anonymous composite type syntax in the FROM clause. See
the instructions in the documentation below.
Documentation
==================================================================
Name
normal_rand(int, float8, float8, int) - returns a set of normally
distributed float8 values
Synopsis
normal_rand(int numvals, float8 mean, float8 stddev, int seed)
Inputs
numvals
the number of random values to be returned from the function
mean
the mean of the normal distribution of values
stddev
the standard deviation of the normal distribution of values
seed
a seed value for the pseudo-random number generator
Outputs
Returns setof float8, where the returned set of random values are normally
distributed (Gaussian distribution)
Example usage
test=# SELECT * FROM
test=# normal_rand(1000, 5, 3, EXTRACT(SECONDS FROM CURRENT_TIME(0))::int);
normal_rand
----------------------
1.56556322244898
9.10040991424657
5.36957140345079
-0.369151492880995
0.283600703686639
.
.
.
4.82992125404908
9.71308014517282
2.49639286969028
(1000 rows)
Returns 1000 values with a mean of 5 and a standard deviation of 3.
==================================================================
Name
crosstabN(text) - returns a set of row_name plus N category value columns
Synopsis
crosstabN(text sql)
Inputs
sql
A SQL statement which produces the source set of data. The SQL statement
must return one row_name column, one category column, and one value
column.
e.g. provided sql must produce a set something like:
row_name cat value
----------+-------+-------
row1 cat1 val1
row1 cat2 val2
row1 cat3 val3
row1 cat4 val4
row2 cat1 val5
row2 cat2 val6
row2 cat3 val7
row2 cat4 val8
Outputs
Returns setof tablefunc_crosstab_N, which is defined by:
CREATE VIEW tablefunc_crosstab_N AS
SELECT
''::TEXT AS row_name,
''::TEXT AS category_1,
''::TEXT AS category_2,
.
.
.
''::TEXT AS category_N;
for the default installed functions, where N is 2, 3, or 4.
e.g. the provided crosstab2 function produces a set something like:
<== values columns ==>
row_name category_1 category_2
---------+------------+------------
row1 val1 val2
row2 val5 val6
Notes
1. The sql result must be ordered by 1,2.
2. The number of values columns depends on the tuple description
of the function's declared return type.
3. Missing values (i.e. not enough adjacent rows of same row_name to
fill the number of result values columns) are filled in with nulls.
4. Extra values (i.e. too many adjacent rows of same row_name to fill
the number of result values columns) are skipped.
5. Rows with all nulls in the values columns are skipped.
6. The installed defaults are for illustration purposes. You
can create your own return types and functions based on the
crosstab() function of the installed library.
The return type must have a first column that matches the data
type of the sql set used as its source. The subsequent category
columns must have the same data type as the value column of the
sql result set.
Create a VIEW to define your return type, similar to the VIEWS
in the provided installation script. Then define a unique function
name accepting one text parameter and returning setof your_view_name.
For example, if your source data produces row_names that are TEXT,
and values that are FLOAT8, and you want 5 category columns:
CREATE VIEW my_crosstab_float8_5_cols AS
SELECT
''::TEXT AS row_name,
0::FLOAT8 AS category_1,
0::FLOAT8 AS category_2,
0::FLOAT8 AS category_3,
0::FLOAT8 AS category_4,
0::FLOAT8 AS category_5;
CREATE OR REPLACE FUNCTION crosstab_float8_5_cols(text)
RETURNS setof my_crosstab_float8_5_cols
AS '$libdir/tablefunc','crosstab' LANGUAGE 'c' STABLE STRICT;
Example usage
create table ct(id serial, rowclass text, rowid text, attribute text, value text);
insert into ct(rowclass, rowid, attribute, value) values('group1','test1','att1','val1');
insert into ct(rowclass, rowid, attribute, value) values('group1','test1','att2','val2');
insert into ct(rowclass, rowid, attribute, value) values('group1','test1','att3','val3');
insert into ct(rowclass, rowid, attribute, value) values('group1','test1','att4','val4');
insert into ct(rowclass, rowid, attribute, value) values('group1','test2','att1','val5');
insert into ct(rowclass, rowid, attribute, value) values('group1','test2','att2','val6');
insert into ct(rowclass, rowid, attribute, value) values('group1','test2','att3','val7');
insert into ct(rowclass, rowid, attribute, value) values('group1','test2','att4','val8');
select * from crosstab3(
'select rowid, attribute, value
from ct
where rowclass = ''group1''
and (attribute = ''att2'' or attribute = ''att3'') order by 1,2;');
row_name | category_1 | category_2 | category_3
----------+------------+------------+------------
test1 | val2 | val3 |
test2 | val6 | val7 |
(2 rows)
==================================================================
Name
crosstab(text, int) - returns a set of row_name
plus N category value columns
Synopsis
crosstab(text sql, int N)
Inputs
sql
A SQL statement which produces the source set of data. The SQL statement
must return one row_name column, one category column, and one value
column.
e.g. provided sql must produce a set something like:
row_name cat value
----------+-------+-------
row1 cat1 val1
row1 cat2 val2
row1 cat3 val3
row1 cat4 val4
row2 cat1 val5
row2 cat2 val6
row2 cat3 val7
row2 cat4 val8
N
number of category value columns
Outputs
Returns setof record, which must defined with a column definition
in the FROM clause of the SELECT statement, e.g.:
SELECT *
FROM crosstab(sql, 2) AS ct(row_name text, category_1 text, category_2 text);
the example crosstab function produces a set something like:
<== values columns ==>
row_name category_1 category_2
---------+------------+------------
row1 val1 val2
row2 val5 val6
Notes
1. The sql result must be ordered by 1,2.
2. The number of values columns is determined at run-time. The
column definition provided in the FROM clause must provide for
N + 1 columns of the proper data types.
3. Missing values (i.e. not enough adjacent rows of same row_name to
fill the number of result values columns) are filled in with nulls.
4. Extra values (i.e. too many adjacent rows of same row_name to fill
the number of result values columns) are skipped.
5. Rows with all nulls in the values columns are skipped.
Example usage
create table ct(id serial, rowclass text, rowid text, attribute text, value text);
insert into ct(rowclass, rowid, attribute, value) values('group1','test1','att1','val1');
insert into ct(rowclass, rowid, attribute, value) values('group1','test1','att2','val2');
insert into ct(rowclass, rowid, attribute, value) values('group1','test1','att3','val3');
insert into ct(rowclass, rowid, attribute, value) values('group1','test1','att4','val4');
insert into ct(rowclass, rowid, attribute, value) values('group1','test2','att1','val5');
insert into ct(rowclass, rowid, attribute, value) values('group1','test2','att2','val6');
insert into ct(rowclass, rowid, attribute, value) values('group1','test2','att3','val7');
insert into ct(rowclass, rowid, attribute, value) values('group1','test2','att4','val8');
SELECT *
FROM crosstab(
'select rowid, attribute, value
from ct
where rowclass = ''group1''
and (attribute = ''att2'' or attribute = ''att3'') order by 1,2;', 3)
AS ct(row_name text, category_1 text, category_2 text, category_3 text);
row_name | category_1 | category_2 | category_3
----------+------------+------------+------------
test1 | val2 | val3 |
test2 | val6 | val7 |
(2 rows)
==================================================================
-- Joe Conway
45e2544584