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README.tablefunc

/*
 * 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.

    connectby(text relname, text keyid_fld, text parent_keyid_fld,
                text start_with, int max_depth [, text branch_delim])
      - returns keyid, parent_keyid, level, and an optional branch string
      - 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)

==================================================================
Name

connectby(text, text, text, text, int[, text]) - returns a set
    representing a hierarchy (tree structure)

Synopsis

connectby(text relname, text keyid_fld, text parent_keyid_fld,
            text start_with, int max_depth [, text branch_delim])

Inputs

  relname

    Name of the source relation

  keyid_fld

    Name of the key field

  parent_keyid_fld

    Name of the key_parent field

  start_with

    root value of the tree input as a text value regardless of keyid_fld type

  max_depth

    zero (0) for unlimited depth, otherwise restrict level to this depth

  branch_delim

    If optional branch value is desired, this string is used as the delimiter.
    When not provided, a default value of '~' is used for internal 
    recursion detection only, and no "branch" field is returned.

Outputs

  Returns setof record, which must defined with a column definition
  in the FROM clause of the SELECT statement, e.g.:

    SELECT * FROM connectby('connectby_tree', 'keyid', 'parent_keyid', 'row2', 0, '~')
      AS t(keyid text, parent_keyid text, level int, branch text);

    - or -

    SELECT * FROM connectby('connectby_tree', 'keyid', 'parent_keyid', 'row2', 0)
      AS t(keyid text, parent_keyid text, level int);
    
Notes

  1. keyid and parent_keyid must be the same data type

  2. The column definition *must* include a third column of type INT4 for
     the level value output

  3. If the branch field is not desired, omit both the branch_delim input
     parameter *and* the branch field in the query column definition. Note
     that when branch_delim is not provided, a default value of '~' is used
     for branch_delim for internal recursion detection, even though the branch
     field is not returned.

  4. If the branch field is desired, it must be the fourth column in the query
     column definition, and it must be type TEXT.

  5. The parameters representing table and field names must include double
     quotes if the names are mixed-case or contain special characters.


Example usage

CREATE TABLE connectby_tree(keyid text, parent_keyid text);

INSERT INTO connectby_tree VALUES('row1',NULL);
INSERT INTO connectby_tree VALUES('row2','row1');
INSERT INTO connectby_tree VALUES('row3','row1');
INSERT INTO connectby_tree VALUES('row4','row2');
INSERT INTO connectby_tree VALUES('row5','row2');
INSERT INTO connectby_tree VALUES('row6','row4');
INSERT INTO connectby_tree VALUES('row7','row3');
INSERT INTO connectby_tree VALUES('row8','row6');
INSERT INTO connectby_tree VALUES('row9','row5');

-- with branch
SELECT * FROM connectby('connectby_tree', 'keyid', 'parent_keyid', 'row2', 0, '~')
 AS t(keyid text, parent_keyid text, level int, branch text);
 keyid | parent_keyid | level |       branch
-------+--------------+-------+---------------------
 row2  |              |     0 | row2
 row4  | row2         |     1 | row2~row4
 row6  | row4         |     2 | row2~row4~row6
 row8  | row6         |     3 | row2~row4~row6~row8
 row5  | row2         |     1 | row2~row5
 row9  | row5         |     2 | row2~row5~row9
(6 rows)

-- without branch
SELECT * FROM connectby('connectby_tree', 'keyid', 'parent_keyid', 'row2', 0)
 AS t(keyid text, parent_keyid text, level int);
 keyid | parent_keyid | level
-------+--------------+-------
 row2  |              |     0
 row4  | row2         |     1
 row6  | row4         |     2
 row8  | row6         |     3
 row5  | row2         |     1
 row9  | row5         |     2
(6 rows)

==================================================================
-- Joe Conway

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