Also try to improve readability and performance.

> be a useful function for many users.   However, I found the fact that
> if connectby_tree has the following data, connectby() tries to search the end
> of roots without knowing that the relations are infinite(-5-9-10-11-9-10-11-)
.
> I hope connectby() supports a check routine to find infinite relations.
>
>
> CREATE TABLE connectby_tree(keyid int, parent_keyid int);
> INSERT INTO connectby_tree VALUES(1,NULL);
> INSERT INTO connectby_tree VALUES(2,1);
> INSERT INTO connectby_tree VALUES(3,1);
> INSERT INTO connectby_tree VALUES(4,2);
> INSERT INTO connectby_tree VALUES(5,2);
> INSERT INTO connectby_tree VALUES(6,4);
> INSERT INTO connectby_tree VALUES(7,3);
> INSERT INTO connectby_tree VALUES(8,6);
> INSERT INTO connectby_tree VALUES(9,5);
>
> INSERT INTO connectby_tree VALUES(10,9);
> INSERT INTO connectby_tree VALUES(11,10);
> INSERT INTO connectby_tree VALUES(9,11);    <-- infinite
>

The attached patch fixes the infinite recursion bug in
contrib/tablefunc/tablefunc.c:connectby found by Masaru Sugawara.

test=# SELECT * FROM connectby('connectby_tree', 'keyid',
'parent_keyid', '2', 4, '~') AS t(keyid int, parent_keyid int, level
int, branch text);
  keyid | parent_keyid | level |   branch
-------+--------------+-------+-------------
      2 |              |     0 | 2
      4 |            2 |     1 | 2~4
      6 |            4 |     2 | 2~4~6
      8 |            6 |     3 | 2~4~6~8
      5 |            2 |     1 | 2~5
      9 |            5 |     2 | 2~5~9
     10 |            9 |     3 | 2~5~9~10
     11 |           10 |     4 | 2~5~9~10~11
(8 rows)

test=# SELECT * FROM connectby('connectby_tree', 'keyid',
'parent_keyid', '2', 5, '~') AS t(keyid int, parent_keyid int, level
int, branch text);
ERROR:  infinite recursion detected

I implemented it by checking the branch string for repeated keys
(whether or not the branch is returned). The performance hit was pretty
minimal -- about 1% for a moderately complex test case (220000 record
table, 9 level tree with 3800 members).

Joe Conway

that the right flavors of largefile-related definitions are seen.
Most of these changes are probably unnecessary, but better safe than
sorry.

function, connectby(), which can serve as a reference implementation for

the changes made in the last few days -- namely the ability of a
function to return an entire tuplestore, and the ability of a function
to make use of the query provided "expected" tuple description.

Description:

   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.

Joe Conway

(overlaying low byte of page size) and add HEAP_HASOID bit to t_infomask,
per earlier discussion.  Simplify scheme for overlaying fields in tuple
header (no need for cmax to live in more than one place).  Don't try to
clear infomask status bits in tqual.c --- not safe to do it there.  Don't
try to force output table of a SELECT INTO to have OIDs, either.  Get rid
of unnecessarily complex three-state scheme for TupleDesc.tdhasoids, which
has already caused one recent failure.  Improve documentation.

to the table function, thus preventing memory leakage accumulation across
calls.  This means that SRFs need to be careful to distinguish permanent
and local storage; adjust code and documentation accordingly.  Patch by
Joe Conway, very minor tweaks by Tom Lane.

composite type capability makes it possible to create a system view
based on a table function in a way that is hopefully palatable to
everyone. The attached patch takes advantage of this, moving
show_all_settings() from contrib/tablefunc into the backend (renamed
all_settings(). It is defined as a builtin returning type RECORD. During
initdb a system view is created to expose the same information presently
available through SHOW ALL. For example:

test=# select * from pg_settings where name like '%debug%';
          name          | setting
-----------------------+---------
  debug_assertions      | on
  debug_pretty_print    | off
  debug_print_parse     | off
  debug_print_plan      | off
  debug_print_query     | off
  debug_print_rewritten | off
  wal_debug             | 0
(7 rows)


Additionally during initdb two rules are created which make it possible
to change settings by updating the system view -- a "virtual table" as
Tom put it. Here's an example:

Joe Conway

three functions which exercise the tablefunc API.

show_all_settings()
   - returns the same information as SHOW ALL, but as a query result

normal_rand(int numvals, float8 mean, float8 stddev, int seed)
   - returns a set of normally distributed float8 values
   - This routine implements Algorithm P (Polar method for normal
     deviates) from Knuth's _The_Art_of_Computer_Programming_, Volume 2,
     3rd ed., pages 122-126. Knuth cites his source as "The polar
     method", G. E. P. Box, M. E. Muller, and G. Marsaglia,
     _Annals_Math,_Stat._ 29 (1958), 610-611.

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 directions
     in the README.

Joe Conway