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
