Hi Tony, thanks for taking your time and your extensive reply. Perhaps I've made it too complicated. Ok, I try to reformulate it. Disclaimer also: I work in a corporate environment, so I'm not completely free in the tools I am allowed to use (to my surprise, Node.js is ok - yessss!) and how much information I can disclose.
Let's put it that way: I have set up an internal information repository which contains more or less textual information only so far. But now and then, I would like to display some figures. And I would have to perform some simple arithmetics with that figures (basically summing up). Let's call the things I am looking at "facilities". A "facility" should be displayed in a templated tiddler, displaying textual and quantitative information. Each "facility" can feature several "units" (that's the 1:n relation), figures for which should also be displayed and/or shown as a grand total. The data for the facility/unit information should initially come from an Excel table. For further use (the CRUD part), I would like to create a TW-based interface. As "facility" is a comprehensive entity for my purposes, I thought it would be ok to store it in a nested JSON tiddler, i.e. store the units per facility in a JSON array. This, of course, breaks the RDBMS dogma, but it saves me from having to fiddle with primary keys. Mimicking a RDBMS in TW is definitely not a rabbit hole I want to jump into. If I needed something like that, I would try if I could connect a DB backend via Node.js (in my special environment I would end up with SQLite or ODBC), and let this do the grunt work. All this being said, here's the core of my question: Accessing nested JSON data using Joshua Fontenay's JSONMANGLER plugin works great, as long as the index position is known, but I need a way to determine the length of a variable-length array in a JSON structure, for not running out-of-bounds while looping into the nested data. I understand $:/History is such a variable-length array, and thanks for pointing me at this. In that case, maybe I need to look up how data are retrieved from there. I know, as a workaround, I still could store the number of units as a data field in the JSON structure, but then I would have to take care of it programatically, which I want to avoid. Thanks again and apologies for any confusion I caused Werner TW Tones schrieb am Freitag, 10. Juli 2020 um 01:19:01 UTC+2: > Werner, > > Despite clearly having a lot in common with an understanding of databases > I don't completely follow you need or argument here. However I believe I > can offer you some helpful leads. > > One part that confuses me is your 1:n or one to many, I have already build > one to one, one to many and many to many half a dozen ways without a data > tiddler in tiddlywiki. What is the particular issue here? > > First look at tiddlywikis existing functionality. > > - The history mechanism stores tiddler titles and more during a > session in the $:/historyList this may be an analogue > - The Import and export mechanism extract and package tiddlers as json > representations > - Mohammad's Trash Plugin moves deleted tiddlers into another > structure to keep them aside, I think it is JSON as well. > - In my demo site here > <https://anthonymuscio.github.io/ActiveTiddler.html> the active > tiddler process extracts titles from the history list using splitregexp > not > standard JSON as the key is not unique > > However It would not necessarily be too concerned about using tiddlers > unless your number will be truly astounding in numbers. We had a 66,000 > word tiddler example in the last year and that was single file. > > Speculation > > If you packed more static tiddlers (eg a reference table) into a plugin > and access them as shadow tiddlers you are effectively packing them into a > json file and allow yourself to edit exceptions and the database becomes > the combination of the packaged and overwritten providing a lot of > flexibility to your design. In effect you CRUD will make use of standard > tiddlywiki features, just treat the records like standard tiddlers. The D > or delete of CRUD could get smart (adding and removing from JSON) or you > could simply flag deleted tiddlers as such and treat them as deleted with > an occasional rebuild recommended after N tiddlers are flagged as deleted. > > I can already foresee a lot of sophisticated features being possible > including tracing and logs, difference engines, database snapshot at a > point in time and more. I have recently designed an alternative to shadow > tiddlers I call ghost tiddlers that may also be a useful algorithm. > > Offer > I as a tiddlywiki superuser, I am investing totally in the TiddlyWiki > platform, if you are interested in collaboration to build a database model > process, making full use tiddlywiki's unique features I think it will be a > good investment in the future. > > Lets start the conversation. > > Regards > Tony > > > > > On Friday, July 10, 2020 at 5:38:31 AM UTC+10, Werner wrote: >> >> Dear all, heavy user and rare poster here. Using TW has become a daily >> treat for me, but I have managed to still stay at the surface so far. Now, >> I have to dive in deeper. >> >> I have been using TW so far to store semi-structured information, but now >> I need to integrate structured information, i.e. a database featuring an >> 1:n relation. >> >> I thought it might be a good idea using JSON. I also thought, for my >> purposes, I don't want to mimic an RDBMS in TW with all the primary key >> hassles and a deluge of .TID files (I am running TW on Node.js), so I >> wanted to use a JSON tiddler for the entities and use arrays in JSON for >> sub-entities. >> >> I came across Joshua Fontenay's JSONMangler plugin (Kudos, Josh!) and so >> far so good. >> >> BUT >> >> Eventually I want to implement CRUD (create-retrieve-update-delete) >> functionalities for this special data. And I want to display the 1:n >> relation in a single tiddler. And this is where I'm stuck at the moment: >> >> - how to get the total number of array items in a JSON array in order to >> be able to display the 1:n >> >> apart from the variable array length, the JSON structure is fix, so >> everything else should be fairly straightforward. OK, there are some >> numeric fields in the array I need to sum up, but one thing after the >> other... >> >> Any insight would be greatly appreciated >> >> Best, >> Werner >> >> >> -- You received this message because you are subscribed to the Google Groups "TiddlyWiki" group. To unsubscribe from this group and stop receiving emails from it, send an email to tiddlywiki+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/tiddlywiki/ffdf0f49-dd6e-41cb-8a13-aed6544f4f0en%40googlegroups.com.
