I read some more about window functions and now see more clearly that they are an extension to aggregate functions. Now I understand why it makes sense to have a method name for both aggregate and window functions. I'll also go ahead and put window function support in my code next chance I get, rather than wait until I'm totally solid on aggregate functions.
On Wed, Jan 30, 2019, 13:59 Richard Hipp <d...@sqlite.org wrote: > It seems that you distinguish between the xStep and xFinal methods by > the number of argments. xStep as 1+N argument (where N is the number > of function parameters) and xFinal has just 1. > > Dan suggests (and I agree) that this will not extend well to window > functions. It might be better to have an initial argument that is the > "method" name. xStep would 2+N arguments where the first argument is > the string "step" and xFinal has 2 arguments where the first argument > is "final". Then when you go to add the xValue and xInverse routines > for window functions, you will have a convenient way to distinguish > those calls from xStep and xFinal. > > On 1/30/19, Andy Goth <andrew.m.g...@gmail.com> wrote: > > On 1/29/19 1:15 AM, Andy Goth wrote: > >> I wish to define custom aggregate functions in Tcl > > > > Initial implementation: > > > > > https://chiselapp.com/user/andy/repository/sqlite-andy/info/e0689f05d1f8792d > > > > Sample program, intended to be run from the root of a built SQLite tree: > > > > #!/usr/bin/env tclsh > > > > load .libs/libtclsqlite3.so > > > > sqlite3 db > > > > db function incr -deterministic { > > > > apply {{arg} { > > > > incr arg > > > > }} > > > > } > > > > db function list -deterministic -aggregate { > > > > apply {{state args} { > > > > concat $state $args > > > > }} > > > > } > > > > puts [db eval { > > > > SELECT list(column1, ''), incr(42) > > > > FROM (VALUES ('#'), ('#'), (' c '), ('\'), ('\\'), ('{ xx '), > > ('}')) > > }] > > > > db close > > > > # vim: set sts=4 sw=4 tw=80 et ft=tcl: > > > > > > Here's the output: > > > > {{#} {} # {} { c } {} \\ {} {\\} {} \{\ xx\ {} \} {}} 43 > > > > > > Notice that the first # element is brace-quoted and the second one is > > not. This demonstrates TIP 401 compliance (http://tip.tcl.tk/401) in > > recent Tcl. > > > > Before I can call this project finished, I need to update the test suite > > and documentation. But I didn't want to wait for that to release the > > code I've already written, so here you go. > > > > As a separate project, I would like to improve the Tcl script dispatch. > > For several reasons, safeToUseEvalObjv() doesn't really meet its stated > > goal. I have a lot to say about this but should wait until another time > > to go into detail. Let's finish the aggregate function project first. > > > > Another good follow-on project would be adding support for window > > functions. Before I can take that on, I need to gain some experience > > using, let alone writing, window functions. > > > > -- > > Andy Goth | <andrew.m.goth/at/gmail/dot/com> > > _______________________________________________ > > sqlite-users mailing list > > sqlite-users@mailinglists.sqlite.org > > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users > > > > > -- > D. Richard Hipp > d...@sqlite.org > _______________________________________________ > sqlite-users mailing list > sqlite-users@mailinglists.sqlite.org > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users > _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
