Roy Tang

Programmer, engineer, scientist, critic, gamer, dreamer, and kid-at-heart.

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It's Naked CSS day, so this website is super barebones!

All entries tagged software-development.

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Apr 2020

Naked CSS Day

Mar 2020

Browsers and HTTP

Drew Devault wrote a great post/rant about the reckless limitless scope of modern web browsers: I conclude that it is impossible to build a new web browser. The complexity of the web is obscene. The creation of a new web browser would be comparable in effort to the Apollo program or the Manhattan project. For the past year or so, I’ve been thinking about contributing to an open source project.

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Pure CSS Spoilers

I previously had some post that had some content hidden via spoiler tags, using a custom Hugo shortcode. Since I’m an old-school developer I was previously doing this using some Javascript run on load: let elements = document.querySelectorAll(".spoiler_header");, function(el, i) { el.addEventListener( 'click', function( event ) { let nextEl = el.nextElementSibling; let display = getComputedStyle(nextEl)['display']; if (display == 'none') { = 'block'; } else { = 'none'; } }, false); }); This is the modern age however.

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Posted by under post at #software development #css
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Feb 2020

Tales from the Old Web (Development)

There was this great (and long!) article that came out recently about the history of CSS. It reminded me a lot of the old days when I started out in web development. So join me in a walk down memory lane as I reminisce about the trials and tribulations of early web development. (This one isn’t about CSS as much as that linked article.)

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Jan 2020

Flask vs Django

Nov 2019

Is SQL a dying art?

I was helping my brother check some database issues the other week, and he mentioned how impressed he was with how quickly I was able to come up with SQL queries on the fly. I told him that SQL was one of the skills I considered myself to have mastery over. This shouldn’t be surprising given my early career path: for most of my first year working as a software developer, I was working on reports which involved lovingly handcrafted (and oftentimes quite complicated) SQL queries.

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Posted by under post at #software development #sql
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What to do in a production crisis

Despite our best efforts as software developers, it can still happen: production goes down. Or some sort of bug introduces catastrophic data error. Hopefully you have a support/DevOps team to handle the response. If not, the dev team themselves have to step in. This usual means a mad rush to figure out what happened and how to fix it, sometimes during off hours and maybe even into the early morning, all while facing pressure from clients and higher-ups.

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DevNotes: Python's yield

I’ve been using Python for well over 10 years, and I still don’t have an intuitive mastery of one of its keywords: yield. Everytime I see it in someone’s code I need to stop and mentally remind myself what it does. I figured I’d write a devnote to help improve my recall. Typically, yield is used in a function with a loop, like so: def some_func(lim): for i in range(0, lim): yield i yield means the function returns a “generator” that can be used as an iterable in a loop:

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The Perils of Handover Documentation

A while back I found myself having to figure out how to compile/build/run a mobile application. The developers previously assigned to the project were no longer available to consult with, but they did leave behind some documentation. However, their documentation quality left a lot to be desired. The instructions they left basically amounted to: npm install ionic serve ionic codrova run android/ios Okay, first sign of trouble is that their instructions were basically commands that anyone who knew the app used Ionic would be able to Google.

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Aug 2019

Python: Markov Chains

Back when I was still learning Python in 2008, one of the first “fun” scripts I wrote was a text generator using Markov chains. I’d run it against all the chat logs I had with people at work and serve the results from a webserver on my computer. THe results were often amusing and sometimes hilarious. Since I’ve been going through my old scripts lately, I thought I’d update that script to Python 3 (read: add parentheses around print params and use pathlib) and run it against all the posts on this here site.

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Posted by under post at #software development #python
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Devnotes: Python Pathlib

Ever since I started learning Python back in 2008ish, I’ve been using it as my primary scripting language for various tasks such as processing log files, organizing my own file system, processing stuff on this blog, and so on. A lot of it is basically moving files around. In the days of Python 2, that involved a lot of imports of different libraries like os, shutil and glob. It can become a bit messy with so many imports, and I often can’t remember which import I need for a particular case and end up having to search for the documentation (or stackoverflow, let’s not kid ourselves here).

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Devnotes: Migrating Mercurial to Git

Big news in online repositories this week is that Bitbucket is sunsetting support for Mercurial! This might be the death knell for Mercurial, although Git was already the super popular choice before. Back when I started using online source control for my personal coding projects I started out with Bitbucket over Github because they offered unlimited private repos and Mercurial (which I had already tried out before at work, so at first I preferred it over git).

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I recently found myself doing a really small project as sort of a proof of concept/demo for a potential client. It often seems that it might be a waste of time to do something like this since you don’t know if the project will actually push through or maybe the client will want something else. To kind of hedge my bets a bit, I decided to take the opportunity to try out some new technologies so that no matter what I at least learned something from all of this.

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I decided to start doing small “devnotes” on developer stuff I’m doing so I can refer to them later (and also because I feel like I could use more technical content on this blog) Today is about PostgreSQL. I haven’t used it much beyond standard ANSI sql stuff. You won’t always have a graphical interface to access your database, sometimes you need to ssh to prod and query the database from the shell.

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Posted by under post at #devnotes #software development
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Jul 2019

Upgrading a React Native Project

I have a small mobile app that I wrote using React Native (henceforth RN) back in 2017, currently deployed on the Google Play Store and Apple App Store. Shortly before my US trip, I got an email from Google telling me about a required action: By August 1, 2019, all apps that use native code must provide a 64-bit version in addition to the 32-bit version in order to publish an update.

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10X Programmers

The topic of the mythical “10x programmer” has been the topic of discussion recently on tech twitter, due to a thread listing out the supposed signs of being such a mythical beast. 10x engineers Founders if you ever come across this rare breed of engineers, grab them. If you have a 10x engineer as part of your first few engineers, you increase the odds of your startup success significantly. OK, here is a tough question.

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Apr 2019

Learning from failure

Success is not final, failure is not fatal: it is the courage to continue that counts. – Winston Churchill I already typed the above quote into the post, then realized I had already used it before. Whatever, just goes to show, I’m no stranger to failure. I was reminded of this quote because recently I prepared a demo for a project that didn’t push through. At first I was annoyed at the wasted effort, but I realized that I had wisely taken the demo project as an opportunity to learn/sharpen some skills.

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Mar 2019

A Quick Twitter App I Wrote

I wish I had a more concise way to describe it, but I really don’t. Some time ago this guy I follow on Twitter, visakanv wanted to know how to do a certain search: he wanted to know who a given famous person follows on Twitter, and among those, finds the one who follow him (visakanv), so he could network through them. I might not be explaining the concept too well, here’s the thread.

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Lies and marketing

I mentioned before that as an engineer, I’m not fond of marketing. Image credit: (Disclaimer: Liking the Dilbert comics is not an endorsement of Scott Adams’ politics) It’s not that I can’t be good at salesmanship either. I have a good grasp of communication skills and think I have a decent chance of writing good copy. My main issue is that I’ve been exposed many times to sales/marketing practices that just seem dishonest downright or scummy.

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If I could give some advice to someone starting out in their software development career, it would be this: Don’t stay in the same place too long. The first company I worked at, I stayed with them for thirteen years, which I now feel was way too long. I have to admit, the work was hard and challenging, but I was young and had a lot of energy and was willing to work the long hours.

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Another repost from my Quora answers, this time some info for anyone looking to move into programming. What are the pros and cons of making your career in programming? Pros: It is a very rewarding career financially. Software development often ranks in the top 10 highest-earning careers in most countries There is a lot of scope - you could be developing web applications, mobile applications, embedded applications, client-side, server-side, data analysis, artificial intelligence, games, etc It is very difficult to be bored.

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Studying a large project codebase

Given my recent misgivings about Quora, I thought it might be a good idea to cross-post some of my answers from there into this blog, with some edits even. So here’s the first one! (stuff in italics were added during the cross-post) How can you read and study a large software project source code? Attacking a large, existing codebase that you are unfamiliar with can be a daunting endeavor.

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Posted by under post at #quora #Software Development
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Feb 2019

Reddit PH: Software Dev Q&A

I had some free time the other day so I randomly decided to post in the PH subreddit‘s regular afternoon random discussion thread, asking for questions about software development. I ended up typing some longish answers, I thought I’d copy them over to the blog in case anyone was interested. TBH I meant more like StackOverflow type questions with specific technical problems, but I ended up answering mostly career-related questions, which is fine, but disclaimer: I don’t claim to be an expert, these are just my opinions on things.

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Last October I participated in #Hacktoberfest, sponsored by DigitalOcean and Github. It’s a “celebration” to promote open source activity, and basically you just need to submit 5 pull requests to any github repository, and they give away swag to anyone who completes the activity. Microsoft held a [counterpart celebration] where they only require you to submit 1 pull request to any Microsoft repository. I’ve always wanted to start participating in Open Source, but it’s a bit difficult to find a good place to contribute (other than logging issues of course).

read more (386 words)

A while back I started a Twitter trivia bot as a weekend project. That bot is still up and running on Twitter, you can check it out there! But today, I thought I’d write about the answer-checking mechanism used by the bot. It was a bit interesting to me because it was the first nontrivial use I had for Django’s unit testing framework. I’m not too keen on unit testing web functionality (something I still have to learn), but this seemed an appropriate first use of a unit test framework for several reasons:

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Jan 2019

I still Google the most basic things

I’ve been working with Javascript for more than a decade. Last week while helping another developer debug a problem, I had to Google how to check if an element exists in a Javascript array, something superbasic, that one would expect most newbies to know. I’m sure I Google some superbasic thing at least once a week. It’s not embarassing or anything, it’s a common occurrence. I’m surely not alone. Just last night a tweet about this crossed my TL:

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Finding Time to Learn new Things

Someone responded to my post on things to learn in 2019 by asking how one finds the inspiration to learn all of the things. Well, my first answer was that those are just things I find interesting and may look into, but that’s not really an answer for the inspiration part. Software development is a very wide field, one where the amount of things you can learn increases daily, so it’s almost impossible to keep up with everything.

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Git vs CVS

A while back we were tasked with helping a client’s internal dev team to migrate their repositories from Subversion to Git. The distributed VCS seemed ideal for their situation - they had a very small in-house dev team managing contributions from external subcontractors. The main rationale was that their process of merging contributions from the external developers was extremely complicated and often resulted in conflicts that were challenging to merge. Before this, I hadn’t actually used Git too deeply myself (aside from cloning stuff from Github), and especially not in a team setting, so the training one of our other engineers gave them was a good opportunity for me to become familiar with Git as well.

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Tech to Learn in 2019

One of the things about self-identifying as a “Full Stack Developer” or “Solution Architect” is that there’s no shortage of things to learn, and oftentimes it’s good for your career-wise to at least have some passing knowledge of a bunch of technologies. It helps that I really like the field as well. I try to make sure I study or learn at least one new programming language or framework every year (though I am willing to stretch that definition as needed).

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Solution Architect

Although I still primarily identify as a “Full Stack Developer”, during the past few years I’ve also found myself in a role called “Solution Architect”. The thing about being a solution architect is that there isn’t really a clear definition of the role, what it involves, or the scope of responsibility. I suppose it depends largely on the organization and the project. The role mostly involves making techical decisions on a larger scale, like project-wide or organization-wide, rather than on the micro day-to-day technical decisions involved in a typical software development involves.

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Revisiting C++ after a decade

This year I had the dubious privilege of having to work with a C++ project again. Although my college education was in C, that was a completely different animal. I did self-study C++ for a bit back even before I was working, mostly because I was interested in game development even back then. I remember trying some OpenGL and/or DirectX stuff back with good old Borland Turbo-C++ during the DOS days and using the Dev-C++ IDE when I shifted to Windows.

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Posted by under post at #c++ #Software Development
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Dec 2018

Adding Developers to a Late Project

For any nontrivial software project of at least moderate team size, there can be a significant cost to onboarding a new team member, especially at later stages when you are rushing to meet deadlines. The most signifiant cost is of course the communication overhead as described in the Mythical Man Month. Fun story, the CEO of a company once told me they would add more developers to a delayed project to meet the deadline and when I pointed out the increased overhead he said to me that it wasn’t a problem because they would just assign modules to those devs that have minimal dependencies so they don’t have to communicate so much.

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Posted by under post at #devto #Software Development
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Nov 2018

My history in text editors

Text editors (and by extension IDEs) are a programmer’s best friend. I thought I’d look back at a number of text editors I’ve used over the years. (I grew up with Windows, so I won’t list vim/emacs/nano here, even though I’m at least a bit proficient with vim by now. That is, I know how to exit vim.) Notepad – of course, the default editor in Windows. The one we turn to when all else fails.

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Posted by under post at #Tech Life #Software Development
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168 hours vs 10000 hours

According to Malcolm Gladwell’s book Outliers, you need 10,000 hours of continuous sustained practice to become an expert. There are 168 hours in a week. If you never sleep and you eat as you practice, you can become an expert in 60 weeks. (Around 14 months) If you sleep 8 hours a day, you only have 112 hours in a week. If you eat as you practice, you can become an expert in 90 weeks.

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Version Issues

SCM (Software Configuration Management) doesn’t just refer to version control for the software you’re building. It also means controlling the versions of software you depend on. This includes operating system and programming runtimes. Sometimes even minor version differences can cause issues in running your software. I have two example stories to share: One of our clients asked us for help with an upgrade their production servers from CentOS 6.4 to 6.

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Oct 2018

Change and Risk and Governments

Systemic change is difficult. I’m talking about software projects/systems, but there are a lot of parallels with societal systems too, like governments or states. I’ve been in large projects with hundreds of thousands of LOC where a lot of the code was painful to read and full of code smells and so on. It happens over time as projects get maintained by different developers and teams or different enhancements or changes are made.

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Django Blog Application

Ten years ago this month, I started studying Django by trying to build my own blog application. I found the code lying around while I was going through some backups lately. It’s way out of date, it uses an early version of django. I thought of bringing it up to speed, but that didn’t seem practical. Instead, for archival purposes, I cleaned it up a bit and uploaded the code to a github repo.

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Gladwell and Risk Management

Malcolm Gladwell, in an article from 1996 discussing the Challenger disaster, tells us: This kind of disaster is what the Yale University sociologist Charles Perrow has famously called a “normal accident.” By “normal” Perrow does not mean that it is frequent; he means that it is the kind of accident one can expect in the normal functioning of a technologically complex operation. Modern systems, Perrow argues, are made up of thousands of parts, all of which interrelate in ways that are impossible to anticipate.

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Working hours and overtime

Rockstar was in the gaming news recently because they mentioned that some of them had worked 100-hour weeks on their massive sequel to Red Dead Redemption coming out soon (no idea if I’ll play this). The idea of 100 hour weeks seemed insane to me, and it got me thinking: I’ve done some serious overtime before, have I ever gotten close to that amount of work in a week? Luckily, I didn’t have to speculate too much, because I had data (I love data).

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Mentoring in Software Development

Mentoring is one of those tasks that’s to be expected of anyone in a senior software development role. This usually involves reviewing other people’s code, helping them with tough technical issues, and even giving career advice. I’m not sure how good I am when it comes to mentoring other software developers. When I first became technical lead on projects, I got some evaluations from junior developers saying I can be “intimidating”.

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Apr 2018


As a programmer, I’ve always been a big fan of StackOverflow. I asked my first question there and also wrote my first answer in September 2008, which was the month the site launched, so I was pretty much there from the beginning. The site was a huge boon to programmers when it first came out, because the internet as a venue for asking questions and answers back then was a horrible fragmented landscape of small forums and mailing lists and sites like Experts Exchange, all of which were terribly designed.

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Mar 2018

The Setup 2018 Edition

While browsing through my old blog posts, I found one about my setup from 2010. I figured it was a good time to do an update. I like doing posts like these because it provides an easy reference for me to look back and see what I was working with at a certain point in time. What Hardware Do I Use? Desktop. I bought a new desktop rig back in late 2015, here are the specs:

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Feb 2018

According to the documentation here:

If link doesn’t return the domain, the syndication framework will insert the domain of the current site, according to your SITE_ID setting

However, I’m trying to generate a feed of magnet: links. The framework doesn’t recognize this and attempts to append the SITE_ID, such that the links end up like this (on localhost):


Is there a way to bypass this?

Dec 2017

I have a query using MarkLogic node.js that basically boils down to something like this:

.on('data', function(row) {
    console.log("Stream on data");
.on('end', function() {
    console.log("Stream on end");
.on('error', function(error) {

Now, for a certain collection we have in our database, the ‘end’ function doesn’t fire, i.e. I never see “Stream on end” appear in the log. There’s no error or anything, processing just stops. It’s only for this particular collection, other collections seem fine.

If I query documents in that collection directly using other methods such as qb.value() without using qb.collection(), the end event fires correctly. But once I add qb.collection() into the mix (using qb.and), the end event doesn’t fire.

I’m unsure how to debug this, as this is my first time trying to use streams in the nodejs client library. Any advice as to what I can check?


My Coding Approach

I was thinking about my typical approach to coding. When writing a new feature, I tend to implement in the direction of where the data flows, starting from the user interface then to the backend and back to the frontend and wherever else that goes. I will build incrementally, using debugging tools or console printouts to ensure that each step is working correctly. As an example, here’s how I did a recent web-based function:

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How to specify that a column in the schema should be nullable?

I tried adding a nullable attribute:

var myFirstTDE = xdmp.toJSON(
    "template": {
      "context": "/match",
      "collections": ["source1"],
      "rows": [
          "schemaName": "soccer",
          "viewName": "matches",
          "columns": [
              "name": "id",
              "scalarType": "long",
              "val": "id",
              "nullable": 0
              "name": "document",
              "scalarType": "string",
              "val": "docUri"
              "name": "date",
              "scalarType": "date",
              "val": "match-date"
              "name": "league",
              "scalarType": "string",
              "val": "league"


But this gave me a template error:

"message": "TDE-INVALIDTEMPLATENODE: Invalid extraction template node: fn:doc('')/template/array-node('rows')/object-node()/array-node('columns')/object-node()[1]/number-node('nullable')"

For a template defined using XQuery, adding nullable to the column works:


How to do the same thing using JS/Json?

Nov 2017

This is a follow-up to my question here:

So let’s say I have a number of documents structured like this:


         content: {
           name:'Joe Parent',
           children: [
               name: 'Bob Child'
               name: 'Sue Child'
               name: 'Guy Child'
       {permissions : xdmp.defaultPermissions(),
        collections : ['test']})

I want to define a template that would extract triples from these documents defining sibling relationships between the children. For the above example, I would want to extract the following triples (the relationship is two-way):

Bob Child sibling-of Sue Child
Bob Child sibling-of Guy Child
Sue Child sibling-of Bob Child
Sue Child sibling-of Guy Child
Guy Child sibling-of Bob Child
Guy Child sibling-of Sue Child

How can i set up my template to accomplish this?


I’ve been studying the examples here:

I have a set of documents that are structured with a parent name and an array of children nodes with their own names. I want to create a template that generates triples of the form “name1 is-a-parent-of name2”. Here’s a test I tried, with a sample of the document structure:


         content: {
           name:'Joe Parent',
           children: [
               name: 'Bob Child'
               name: 'Sue Child'
       {permissions : xdmp.defaultPermissions(),
        collections : ['test']})


var tde = require("/MarkLogic/tde.xqy");
// Load the user template for user profile rows
var template = xdmp.toJSON(
    "collections": [
        "subject": {
          "val": "xs:string(name)"
        "predicate": {
          "val": "sem:iri('is-parent-of')"
        "object": {
          "val": "xs:string(children/name)"
tde.templateInsert("/templates/test.tde", template);
  [cts.doc( '/test/tde.json' )]

However, the above throws an Exception:

[javascript] TDE-EVALFAILED: tde.nodeDataExtract([cts.doc("/test/tde.json”)]) – Eval for Object='xs:string(children/name)’ returns TDE-BADVALEXPRESSION: Invalid val expression: XDMP-CAST: (err:FORG0001) Invalid cast: (fn:doc("/test/tde.json”)/content/array-node(“children”)/object-node()[1]/text(“name”), fn:doc("/test/tde.json”)/content/array-node(“children”)/object-node()[2]/text(“name”)) cast as xs:string?

What is the proper syntax for extracting array nodes into a triple?

2nd somewhat related question: say I also wanted to have triples of the form “child1 is-sibling-of child2”. For the example above it would be “Bob Child is-sibling-of Sue Child”. What would be the proper syntax for this? I’m not even sure how to begin with this one.

Is TDE even the way to go here? Or is it better to do this programmatically? i.e. on document ingestion, generate those triples inside the document directly?

(If it’s relevant, the ML version being used is 9.)

I’ve been testing migrating one of our systems to Marklogic 9 and using the Optics API.

One of our functions involves grouping claims by member_id, member_name and getting the sums and counts, so I did something like this:

var results = op.fromView('test', 'claims')
  .groupBy(['member_id', 'member_name'], [
         op.count('num_claims', 'claim_no'),
         op.sum('total_amount', 'claim_amount')

Above works fine. The results are of the form

    member_id: 1, 
    member_name: 'Bob', 
    num_claims: 10, 
    total_amount: 500

However, we also have a field “company”, where each claim is filed under a different company. Basically the relevant view columns are claim_no, member_id, member_name, company, claim_amount

I would like to be able to show a column that list the different companies for which the member_id/member_name has filed claims, and how many claims for each company.

i.e. I want my results to be something like:

    member_id: 1, 
    member_name: 'Bob', 
    num_claims: 10, 
    total_amount: 500,
    companies: [
        company: 'Ajax Co',
        num_claims: 8
        company: 'Side Gig',
        num_claims: 2

I tried something like this:

results =, index, array) => {
  var companies = op.fromView('test', 'claims')
    .where(op.eq(op.col('member_id'), member.member_id))
    .groupBy('company', [
      op.count('num_claims', 'claim_no')      
  member.companies = companies;
  return member;

And the output seems correct, but it also executes quite slowly - almost a minute (total number of claim documents is around 120k)

In our previous ML8 implementation, we were pre-generating summary documents for each member - so retrieval was reasonably fast with the downside that whenever we got a bunch of new data, all of the summary documents had to be re-generated. I was hoping that ML9’s optic API would make it easier to do the retrieval/grouping/aggregates on the fly so we wouldn’t have to do that.

In theory, I could just add company to the groupBy fields, then merge the rows in the result query as needed. But the problem with that approach is that I can’t guarantee I’ll get the top 200 by total amount (as was my original query)

So, the question is: Is there a better way of doing this with a reasonable execution time? Or should I just stick to pre-generating the summary documents?