As shown blow,sometime,the elements of embedded array comments will be modified,or an new comment will be inserted into comments as first element,and when these modifications happen,I want to lock something in minimal scope to avoid nasty issue,questions are:
1,What scope to lock is appropriate?
2,How to lock?
{
name: 'Me',
comments: [{
"author": "Joe S.",
"text": "I'm Thirsty"
},
{
"author": "Adder K.",
"text": "old content"
}]
}
RethinkDB automatically locks the document when you do an update, so concurrent modifications to the embedded comments array should not be an issue.
Whether you need additional locking depends on your application and the structure of your data. For example, is one of the fields in the embedded comments a reference to a different document, which must be maintained?
RethinkDB provides an atomicity per document (see http://www.rethinkdb.com/docs/advanced-faq/#how-does-the-atomicity-model-work).
So you can update a nested array (push/update/delete an element in the array) without having to worry about a concurrent operation.
Related
Like many others I've been getting this error when using Sequelize with Express and Express-handlebars:
Handlebars: Access has been denied to resolve the property "first_name" because it is not an "own property" of its parent.
You can add a runtime option to disable the check or this warning:
See https://handlebarsjs.com/api-reference/runtime-options.html#options-to-control-prototype-access for details
Handlebars: Access has been denied to resolve the property "last_name" because it is not an "own property" of its parent.
You can add a runtime option to disable the check or this warning:
See https://handlebarsjs.com/api-reference/runtime-options.html#options-to-control-prototype-access for details
I have found some answers on how to get around this. ie: allowProtoMethods, or adding npm install #handlebars/allow-prototype-access
What I'm curious about is, is there a proper way to handle the data or exclude the proto methods from the sequelize response?
I may not be understanding the issue at hand properly, so if that's the case I apologize. I'm just looking for the "right" way to deal with this.
Edit: To clarify a little further, I'm seeking to do things in a way that will produce the most secure application.
From handlebarsjs.com:
Using these properties may open security holes.
UPDATE!
I'm still trying to work this issue out, but I've noticed an interesting behavior.
Nested objects seem to trigger this issue.
It seems to trigger when the data in a nested object is accessed/rendered on the html page (exa: {{contact.first_name}}
sometimes it will have nested dataValues objects within the object and sometimes it won't.
I'd provide an example including dataValues, but it hasn't displayed like that for a while.
Object being returned:
{
"id": 3,
"email": "email2#email.com",
"password": "$2b$10$fOGiJC6NgUTR4qIt7/R7vuwpaFb3PUl9ks2vHBEkLnOUmRN0tEFue",
"kind": "user",
"createdAt": "2020-08-16T04:37:58.000Z",
"updatedAt": "2020-08-16T04:37:58.000Z",
"Contact": {
"id": 3,
"first_name": "Jane",
"last_name": "Doe",
"gender": "female",
"city": "Long Beach",
"state": "CA",
"zip": 12345,
"phone_number": 1234567891,
"createdAt": "2020-08-16T04:37:58.000Z",
"updatedAt": "2020-08-16T04:37:58.000Z",
"UserId": 3
},
"Props": []
}
I'm not necessarily seeing any other explicit types of data that trigger this error message. (That's not to say that there aren't any, but so far every data type and script that I've passed hasn't caused a problem.)
Data I was having a problem with: This data is from a Sequelize query response shown above.
let hbsObject = {
user: data[0],
contact: data[0].Contact
};
Notes about what happened with this data:
I used a promise to chain several queries at once.
User was queried, and contact was included in that query, so there were nested objects/data in the response. (obviously)
When I tried to render the first and last names from the data I was receiving the error message.
Data that seems to have solved my error:
let user = {
id: data[0].id,
email: data[0].email,
kind: data[0].kind,
createdAt: data[0].createdAt,
updatedAt: data[0].updatedAt,
};
let hbsObject = {
user: user,
contact: data[0].Contact.dataValues,
};
It's strange because sometimes when you view the data in the console, dataValues will be visible, and sometimes it won't. However, when you access it as I showed above the error is removed.
Current Conclusion
The data you are seeking to access on the handlebars page via the handlebars object must not be in a nested object.
What does that mean?
It seems to mean that you must either deconstruct it prior to passing the data to the page either manually (like I did with user) or by sending the data from the object 1 level at a time (like I did with contact).
If anyone can build on this or expand additional information I would greatly appreciate it! I'll edit again if more information becomes available.
UPDATE2
An array of objects is inaccessible as it is a list of objects nested in an array. This makes {{#each x}} a challenge. Individual data has been accessible with the method above.
UPDATE3
I was unable to find any clear solution to this issue. In the end I just allowed the proto methods with the handlebars/allow-prototype-access package.
As long as you're the only one that has access to your template/you absolutely 100% trust whoever also has access to your template, then it shouldn't really be a problem. If that isn't the case, I'd suggest using something other than handlebars for now.
0
If you are using MySQL, sequelize, use raw query options {raw: true} and if you are using relationships, you can use {nest: true}, eg:
users = await User.findAll({
where: { username: "SimonAngatia" },
include: [{ model: Tweet, as: "Tweets" }],
raw: true,
nest: true,
}).catch(errorHandler);
refer here: Sequelize, convert entity to plain object
Could not find this answer online, so decided to post the question then the answer.
I created a table in the capabilities.json file:
"dataRoles": [
{
"displayName": "Stakeholders",
"name": "roleIwant",
"kind": "GroupingOrMeasure"
}
...
"dataViewMappings": [
{
"table": {
"rows": {
"select": [
{
"for": {
"in": "roleIwant"
}
}
]
}
}
}
]
I realized that I could not simply set, for instance, legend data from the first category, because the first category comes from the first piece of data the user drags in, regardless of position. So if they set a bunch of different pieces of data in Power BI online, for instance, then remove one, the orders of everything get messed up. I thought the best way to settle this would be to identify the role of each column and go from there.
When you click on show Dataview, the hierarchy clearly shows:
...table->columns[0]->roles: { "roleIwant": true }
So I thought I could access it like:
...table.columns[0].roles.roleIwant
but that is not the case. I was compiling using pbiviz start from the command prompt, which gives me an error:
error TYPESCRIPT /src/visual.ts : (56,50) Property 'roleIwant' does not exist on type '{ [name: string]: boolean; }'.
Why can I not access this in this way? I was thinking because natively, roles does not contain the property roleIwant, which is true, but that shouldn't matter...
The solution is actually pretty simple. I got no 'dot' help (typing a dot after roles for suggestions), but you can use regular object properties for roles. The command for this case would be:
...table.columns[0].roles.hasOwnProperty("roleIwant")
And the functional code portion:
...
columns.forEach((column) =>{
if(column.roles.hasOwnProperty("roleIwant")){
roleIwantData = dataview.categorical.categories[columns.indexOf(column)].values;
})
If it has the property, it belongs to that role. From here, the data saved will contain the actual values of that role! The only thing I would add on here is that if a column is used for multiple roles, depending on how you code, you may want to do multiple if's to check for the different roles belonging to a column instead of if else's.
If anyone has any further advice on the topic, or a better way to do it, by all means. I searched for the error, all over for ways to access columns' roles, and got nothing, so hopefully this topic helps someone else. And sorry for the wordiness - I tend to talk a lot.
For school I am creating a deckbuilder website based on Magic the gathering. It's the project that decides if I get my degree or not. Trough the website from Deckbrew I have been able to get data like the following:
[
{
"name": "About Face",
"id": "about-face",
"url": "https://api.deckbrew.com/mtg/cards/about-face",
"store_url": "http://store.tcgplayer.com/magic/urzas-legacy/about-face",
"types": [
"instant"
],
"colors": [
"red"
],
"cmc": 1,
"cost": "{R}",
"text": "Switch target creature's power and toughness until end of turn.",
"formats": {
"commander": "legal",
"legacy": "legal",
"vintage": "legal"
},
"editions": [
{
"set": "Urza's Legacy",
"rarity": "common",
"artist": "Melissa A. Benson",
"multiverse_id": 12414,
"flavor": "The overconfident are the most vulnerable.",
"number": "73",
"layout": "normal",
"price": {
"low": 0,
"average": 0,
"high": 0
},
"url": "https://api.deckbrew.com/mtg/cards?multiverseid=12414",
"image_url": "http://mtgimage.com/multiverseid/12414.jpg",
"set_url": "https://api.deckbrew.com/mtg/sets/ULG",
"store_url": "http://store.tcgplayer.com/magic/urzas-legacy/about-face"
}
]
}
]
It's obvious that it's in jSon format. I have found the way to turn this into objects and the structure of the project is 4-layer MVC with entity framework and C#, which is working (kinda)...The problem is the database. I have been working on it for 2 months now and I am not getting any further. The thing I get stuck on is the database. I have not seen much on how to create databases and that's where it goes wrong. I don't get how to build the database. The creation itself would work if I figured out how to include certain things...
1) Formats: if the card is legal in a format, Formats is filled with: "legacy": "legal", "commander":"legal", ... so only the legal formats are included.
2) Types and colors are just plain arrays of words, but since I'm very bad with databases I don't even know how to figure this one out.
3) Editions is something completely different. It's an array of the object Edition which I believe has to have a table of its own. The problem here is that I thought I needed to use a foreign key but since it's an array of Editions I don't really know how to start doing that either.
4) and then there's Price: It always has 3 values: low, average and high which can be 0 if there's no price known.
So here you have it. To me this database is very complex or maybe I am making it too complex. Is there anybody who can help me to get this database organized so I can get on with my project, because I'm so lost at the moment that I feel I am not going to get this ready by the end of next month and that would be awful.
1: No, you should include all.
2: Table with colors, standard m:n binding table in between mapping the card table with the color table. Not knowing how to make a m:n relationship thing makes me thing you skipped all classes... this is fundamental and basic.
3: Seems like "cardedition" is the main table actually, and everything before is a master type table. Not sure- I don't really do magic at all, so I lack what is called domain knowledge. Are cards changed so multiple editions exist? Why is that an array in json?
3: magic values, 0,1,2,3. What is the question?
To me this database is very complex
I suggest you start from scratch (making things easier) and just have maybe 10 or so tables. Go step by step. Follow what you learned, go to 3rd of 4th normal form and go relational.
I understand that JOINs are either not possible or frowned upon in document databases. I'm coming from a relational database background and trying to understand how to handle such scenarios.
Let's say I have an Employees collection where I store all employee related information. The following is a typical employee document:
{
"id": 1234,
"firstName": "John",
"lastName": "Smith",
"gender": "Male",
"dateOfBirth": "3/21/1967",
"emailAddresses":[
{ "email": "johnsmith#mydomain.com", "isPrimary": "true" },
{ "email": "jsmith#someotherdomain.com", "isPrimary": "false" }
]
}
Let's also say, I have a separate Projects collection where I store project data that looks something like that:
{
"id": 444,
"projectName": "My Construction Project",
"projectType": "Construction",
"projectTeam":[
{ "_id": 2345, "position": "Engineer" },
{ "_id": 1234, "position": "Project Manager" }
]
}
If I want to return a list of all my projects along with project teams, how do I handle making sure that I return all the pertinent information about individuals in the team i.e. full names, email addresses, etc?
Is it two separate queries? One for projects and the other for people whose ID's appear in the projects collection?
If so, how do I then insert the data about people i.e. full names, email addresses? Do I then do a foreach loop in my app to update the data?
If I'm relying on my application to handle populating all the pertinent data, is this not a performance hit that would offset the performance benefits of document databases such as MongoDB?
Thanks for your help.
"...how do I handle making sure that I return all the pertinent information about individuals in the team i.e. full names, email addresses, etc? Is it two separate queries?"
It is either 2 separate queries OR you denormalize into the Project document. In our applications we do the 2nd query and keep the data as normalized as possible in the documents.
It is actually NOT common to see the "_id" key anywhere but on the top-level document. Further, for collections that you are going to have millions of documents in, you save storage by keeping the keys "terse". Consider "name" rather than "projectName", "type" rather than "projectType", "pos" rather than "position". It seems trivial but it adds up. You'll also want to put an index on "team.empId" so the query "how many projects has Joe Average worked on" runs well.
{
"_id": 444,
"name": "My Construction Project",
"type": "Construction",
"team":[
{ "empId": 2345, "pos": "Engineer" },
{ "empId": 1234, "pos": "Project Manager" }
]
}
Another thing to get used to is that you don't have to write the whole document every time you want to update an individual field or, say, add a new member to the team. You can do targeted updates that uniquely identify the document but only update an individual field or array element.
db.projects.update(
{ _id : 444 },
{ $addToSet : "team" : { "empId": 666, "position": "Minion" } }
);
The 2 queries to get one thing done hurts at first, but you'll get past it.
Mongo DB is a document storage database.
It supports High Availability, and Scalability.
For returning a list of all your projects along with project team(details),
according to my understanding, you will have to run 2 queries.
Since mongoDb do not have FK constraints, we need to maintain it at the program level.
Instead of FK constraints,
1) if the data is less, then we can embed the data as a sub document.
2) rather than normalized way of designing the db, in MongoDb we need to design according to the access pattern. i.e. the way we need to query the data more likely. (However time for update is more(slow), but at the user end the performance mainly depends on read activity, which will be better than RDBMS)
The following link provides a certificate course on mongo Db, free of cost.
Mongo DB University
They also have a forum, which is pretty good.
I'm at a loss as to how to map a document for search with the following structure:
{
"_id": "007ff234cb2248",
"ids": {
"source1": "123",
"source2": "456",
"source3": "789"
}
"names": [
{"en":"Example"},
{"fr":"exemple"},
{"es":"ejemplo"},
{"de":"Beispiel"}
],
"children" : [
{
"ids": {
"source1": "CXXIII",
"source2": "CDLVI",
"source3": "DCCLXXXIX",
}
names: [
{"en":"Example Child"},
{"fr":"exemple enfant"},
{"es":"Ejemplo niño"},
{"de":"Beispiel Kindes"}
]
}
],
"relatives": {
// Typically no "ids" at this level.
"relation": 'uncle',
"children": [
{
"ids": {
"source1": "0x7B",
"source2": "0x1C8",
"source3": "0x315"
},
"names": [
{"en":"Example Cousin"},
{"fr":"exemple cousine"},
{"es":"Ejemplo primo"},
{"de":"Beispiel Cousin"}
]
}
]
}
}
The child object may appear in the children section directly, or further nested in my document as uncle.children (cousins, in this case). The IDs field is common to levels one (the root), level two (the children and the uncle), and to level three (the cousins), the naming structure is also common to levels one and three.
My use-case is to be able to search for IDs (nested objects) by prefix, and by the whole ID. And also to be able to search for child names, following an (as yet undefined) set of analyzer rules.
I haven't been able to find a way to map these in any useful way. I don't believe I'll have much success using the same technique for ids and names, as there's an extra level of mapping between names and the document root.
I'm not even certain that it is even mappable. I believe at least in principle that the ids should be mappable as terms, and perhaps that if I index the names as terms in some way, too.
I'm simply at a loss, and the documentation doesn't seem to cover anything like this level of complex mapping.
I have limited (read: no) control of the document as it's coming from the CouchDB river, and the upstream application already relies on this format, so I can't really change it.
I'm looking for being able to search by the following pseudo conditions, all of which should match:
ID: "123"
ID by source (I don't know how best to mark this up in pseudo language)
ID prefix: "CDL"
Name: "Example", "Example Child"
Localized name (I don't even know how best to pseudo-mark this up!
The specifics of tokenising and analysis I can figure out for myself, when I at least know how to map
Objects when both the key and the value of the object properties are important
Enumerable objects when the key and value are important.
If the mapping from an ID to its children is 1-to-many, then you could store the children's names in a child field, as a field can have multiple values. Each document would then have an ID field, possibly a relation field, and zero or more child fields.