I have been loosely following this thread and thought I would share my first
use of C_OBJECT. Many years ago I inherited a 4D database that David Adams, yes
you David, had done some work on. Specifically he had crated a web interface
for it and used much of what he talked about in one of his early books on the
subject of 4D and the web.
David used a set of routines to parse both incoming URL parameters name value
pairs, as well as form field name value pairs into parallel arrays. I just
recently modified his code to instead parse them into C_Objects. I did this as
I was about to implement a very large complex query to respond to requests for
records from a table of 50,000 records with up to 30 possible filters or search
parameters involving multiple related tables.
I must say that using C_Objects for the query made building the query much
easier and with fewer lines of code. In the web app the filters are loaded into
Dictionaries, which I combine into a single dictionary which is sent as a form
in the request to 4D. Parsed into a C_Object…
QUERY([Project];[Project]ID>0;*)
If (OB Get(oFormFieldPrameters;"pfTitle")#"")
QUERY([Project]; & ;[Project]Project_Title=OB
Get(oFormFieldPrameters;"pfTitle";*))
End if
If (OB Get(oFormFieldPrameters;"pfConsultants")#"")
QUERY([Project]; & ;[Project]Consultants=OB
Get(oFormFieldPrameters;"pfConsultants";*))
End if
//..... etc. 30 times
QUERY([Project])
Could of done it with the parallel arrays, but this is far more elegant and
perhaps even more efficient.
John
> On Jul 19, 2017, at 11:39 PM, JPR via 4D_Tech <4d_tech@lists.4d.com> wrote:
>
>
>
> [JPR]
>
> Hi Guys,
>
> The exact thing that I've explained was how to use objects to get Associative
> Arrays in 4D. Associative Arrays are widely used in other languages like PHP
> or JavaScript.
>
> In computer science, an Associative Array is an abstract data type composed
> of a collection of (key, value) pairs, such that each possible key appears
> just once in the collection. In 4D, the JSON-type Objects are perfect for
> Associative Arrays.
>
> In many case, you will have 2 parallel arrays, let's say one for the product
> code ($arCodes), and one for the product name ($arNames). You want to find
> the name for a specific code (classic 4D way)
>
> - You create the array with a loop, adding elements pairs $myCode and $myName:
>
> $k:=Find in array($arCodes;$myCode)
> If ($k>0)
> $arNames{$k}:=$myName
> Else
> APPEND TO ARRAY($arCodes;$myCode)
> APPEND TO ARRAY($arNames;$myName)
> End if
>
> - Then you can find a name from a code:
>
> $k:=Find in array($arCodes;$myCode)
> If ($k>0)
> $myName:=$arNames{$k}
> Else
> $myName:=""
> End if
>
> Now if you use an Object:
>
> C_OBJECT($myArray)
>
> You create the array with a loop:
>
> OB SET($myArray;$myCode;$myName)
>
> -and you find with:
>
> $myName:=OB Get($myArray;$myCode}
>
> ...much simpler, and much faster! Why is it faster? With a classic array, the
> Find in array command has to parse the entire array, element per element,
> until the correct element is found (Except in case of a Sorted array, but
> sometimes you can't sort the array because the index of an element can be
> meaningful for your method)
>
> In case of an object, the properties are 'indexed' by using an internal Hash
> table, so the access to one particular Property doesn't need a sequential
> parsing of the list of values, but an almost direct access. I confirm what
> Justin says, that is to say that the bigger will be the array, the more
> efficient will be associative arrays compared with classic parsing of arrays.
>
> My very best,
>
> JPR
>
>
>
>> Message: 7
>> Date: Mon, 17 Jul 2017 11:43:12 -0700
>> From: Justin Leavens <jus...@jitbusiness.com>
>> To: 4D iNug Technical <4d_tech@lists.4d.com>
>> Subject: Re: Arrays vs Object for Key/Value pair lookups
>> Message-ID:
>> <CABwcA3un5GoYVWrFeRXzpm8bNuOtSdaymO9=byk-d_c1vp5...@mail.gmail.com>
>> Content-Type: text/plain; charset="UTF-8"
>>
>> I did a 2014 Summit presentation (5 JSON Tips) which should be available
>> for download that demonstrated the benefits of using objects for key/value
>> pair cache lookups, but in the end it’s pretty easy to demonstrate. The
>> benefits start to show up with a few hundred keys, but at 100,000 it’s
>> easily 20x faster looking up object keys as opposed to find in array in
>> interpreted. And when you compile, it’s literally hundred of times faster
>> (400-500x) at 100k keys - and the benefits just get bigger and bigger with
>> more keys. That’s both for filling the cache and for retrieving values
>> (objects save you from having to check if a key is already in the array
>> before adding it).
>>
>> --
>> Justin Leavens
>> jus...@jitbusiness.com (818) 986-7298 x <//(818) 986-7298 x301>701
>> Just In Time Consulting, Inc.
>> Custom software for unique businesses
>> http://www.linkedin.com/in/justinleavens
>>
>> On July 17, 2017 at 3:46:26 AM, Peter Jakobsson via 4D_Tech (
>> 4d_tech@lists.4d.com) wrote:
>>
>> Hi
>>
>> I remember at last year’s summit, JPR was emphasising how objects were far
>> more optimised than arrays for doing lookups over large numbers of key
>> value pairs.
>>
>> e.g. we usually do this:
>>
>> $x:=find in array(myKEYS;”product_code_x”)
>>
>> if($x>0)
>> $0:=myPRICES{$x}
>> end if
>>
>> How do people prefer to do this with objects ? Enumerate the keys in some
>> systematic way and then populate the object like this >
>>
>> For($i;1;$SIZE)
>>
>> $key:=string($i)
>> $value:=myarrayVAL{$i}
>> OB SET($object;$key;$value)
>>
>> End For
>>
>> Then for retreiving:
>>
>> $key:=string($1)
>>
>> $0:=OB Get($object;$key)
>>
>> …or was JPR suggesting we use object arrays and do some kind of “find” over
>> the object arrays ?
>>
>> Best Regards
>>
>> Peter
>>
>
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