Is it possible to construct aggregate functions using embedded R? Would the syntax be: "create aggregate function"? I need to pass in a pair of aligned vectors/columns to compute weighted percentiles.
I've held off on taking the R route for performance reasons, but I don't see how to pass multiple vectors into the new sub* aggregate implementation.
All of the aggregate functions in gdk_agg.c take a single column and I don't know if it is possible to alter the interface to pass in multiples.
Thanks,
Dave
-----Original Message-----
From: Roberto Cornacchia [roberto.cornacchia@gmail.commailto:roberto.cornacchia@gmail.com]
Sent: Wednesday, May 04, 2016 04:59 AM Eastern Standard Time
To: Communication channel for MonetDB users
Subject: Re: PCRE: references to captures in replace string
Another option is to use R. This is available in Jul2015 branch, and is very easy (https://www.monetdb.org/content/embedded-r-monetdbhttps://urldefense.proofpoint.com/v2/url?u=https-3A__www.monetdb.org_content_embedded-2Dr-2Dmonetdb&d=CwMFaQ&c=j-EkbjBYwkAB4f8ZbVn1Fw&r=8_GYjk1edsyLJlNaxMxYxBJsviF3JXYvwDK42uy5KWU&m=CqtgVJpkJoop7G_7izH9LywiM82AR0XCNvGu0ipkFuo&s=cMjL1PD_6AwNjME5KXxpxTCzfole4bSqgnp4uolKgoY&e=)
CREATE FUNCTION r_replace(s STRING, p STRING, r STRING) RETURNS STRING LANGUAGE R {
sub(p,r,s)
};
sql>select r_replace('Apple Pear', '^([a-zA-Z]+)\\s*([a-zA-Z]+)$', '\\2 \\1');
+------------------------+
| r_replace_single_value |
+========================+
| Pear Apple |
+------------------------+
It works out of the box on columns:
select r_replace(value, '^.*(\d).*$','\\1%\\2') from obj_string limit 100;
And luckily without loops:
X_10:bat[:oid,:str] := batrapi.eval(nil,"{\n sub(p,r,s)\n};",X_9,A0,A1);
Still not very fast - I've just tried on 11M strings, 45s - probably because strings are fully copied, but for now this seems the easiest workaround.
It would be great to have it working on pcre though.
Roberto
On 4 May 2016 at 10:31, Roberto Cornacchia mailto:roberto.cornacchia@gmail.com> wrote:
An interesting workaround for now could be to implement a simple UDF in python, to let python perform the regex processing: https://www.monetdb.org/blog/embedded-pythonnumpy-monetdbhttps://urldefense.proofpoint.com/v2/url?u=https-3A__www.monetdb.org_blog_embedded-2Dpythonnumpy-2Dmonetdb&d=CwMFaQ&c=j-EkbjBYwkAB4f8ZbVn1Fw&r=8_GYjk1edsyLJlNaxMxYxBJsviF3JXYvwDK42uy5KWU&m=CqtgVJpkJoop7G_7izH9LywiM82AR0XCNvGu0ipkFuo&s=USK84Sl9Muw1-qalA5A9ju8ZlqTAQhLAjZpaBBU8-rw&e=
Unfortunately this is for now only available in a separate branch which is kept in sync with default. For me this is no option because I need to rely on a stable MonetDB version. But perhaps for other it is an option.
On 26 April 2016 at 16:57, imad hajj chahine mailto:imad.hajj.chahine@gmail.com> wrote:
I still find this to be an interested feature to add, as its very useful in string date manipulation.
On Tue, Apr 26, 2016 at 5:28 PM, Roberto Cornacchia mailto:roberto.cornacchia@gmail.com> wrote:
I found this thread from October 2015 where Sjoerd concludes that back references replacement is not implemented in the MonetDB wrapper: https://www.monetdb.org/pipermail/users-list/2015-October/008492.htmlhttps://urldefense.proofpoint.com/v2/url?u=https-3A__www.monetdb.org_pipermail_users-2Dlist_2015-2DOctober_008492.html&d=CwMFaQ&c=j-EkbjBYwkAB4f8ZbVn1Fw&r=8_GYjk1edsyLJlNaxMxYxBJsviF3JXYvwDK42uy5KWU&m=CqtgVJpkJoop7G_7izH9LywiM82AR0XCNvGu0ipkFuo&s=-2C6SmdbU2YUQPzV0Y4tHbMAO_qimRAh1LYz_CmnnVk&e=
Probably that is still the case?
On 20 April 2016 at 16:35, Roberto Cornacchia mailto:roberto.cornacchia@gmail.com> wrote:
After declaring a wrapper for pcre.replace:
sql>create function pcre_replace(s string, pattern string, repl string, flags string) returns string external name pcre."replace";
operation successful (6.187ms)
I cannot get replacements with references to captures work (but the code in pcre.c seems to support it):
sql>select pcre_replace('Apple Pear', '^([a-zA-Z]+)\\s*([a-zA-Z]+)$', '\\1 \\2', '');
+---------------------------+
| pcre_replace_single_value |
+===========================+
| \1 \2 |
+---------------------------+
1 tuple (0.309ms)
The pattern is matched, but the back references are replaced literally.
Am I not getting the syntax correct?
From http://www.pcre.org/original/doc/html/pcresyntax.htmlhttps://urldefense.proofpoint.com/v2/url?u=http-3A__www.pcre.org_original_doc_html_pcresyntax.html&d=CwMFaQ&c=j-EkbjBYwkAB4f8ZbVn1Fw&r=8_GYjk1edsyLJlNaxMxYxBJsviF3JXYvwDK42uy5KWU&m=CqtgVJpkJoop7G_7izH9LywiM82AR0XCNvGu0ipkFuo&s=1w0JvVy_zYBkYl-zfHDgynjLIdhHUAILmVoBG7XimvA&e= I see I could use any of \1, \g1, \g{1] for back references, but none seem to work.
Roberto
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