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QUESTION
Let's say I have a canvas where there are various objects I can add in, such as a/an:
- Drawing
- Image
- Chart
- Note
- Table
For each object I need to store the dimensions and the layer order, for example something like this:
- ObjectID
- LayerIndex
- Dimensions ((x1, y1), (x2, y2))
Each of the objects have vastly different properties and so are stored in different tables (or classes or whatever). Would it be possible to store this into a relational database, and if so, how could it be done? In JSON it would be something like this:
...ANSWER
Answered 2021-Dec-05 at 03:53You have many options as shown below.
There is not much difference in which one you pick, but I would avoid the multi-table design which is the one you said. An object type with 100 properties would be scattered in 101 tables for no gain. 101 disk page accesses for each object type being read. That's unnecessary (if those pages are cached then this problem would be lesser than otherwise but is still waste).
Even dual table is not really necessary if you don't wish to filter things like 'all objects with color=red', but I guess performance is not so urgent to reach to this point, other things matters more, or other bottlenecks have more influence in performance, so pick the one of the no-more-than-dual-table that fits best for you.
Single table - flexible schema per object type objlayerindex type props x0 y0 x1 y1 0 drawing {color:#00FF00,background-color:#00FFFF} 1 2 3 4 1 chart {title:2021_sales,values:[[0,0],[3,4]]} 11 22 33 44- in props the keys are used for flexibility, different objects of the same type may have different keys, for example a chart without subtitle can omit this key.
- this schema is fixed - drawing always has color+backgroundcolor; chart always have title+values; etc - less space used but changing schema involves some work on already existing data.
- here we assume that property ordering is not important. If it is, an extra column
propertyindex
would be needed. For those who love normalization, it is possible also to takepropertyname
out of this table to apropertykey-propertydescription
and reference it by itspropertykey
.
- Specifically this kind of data can be normalized one extra level:
You can also use non-relational formats.
Document (Json) StoreQUESTION
I need to remove a child object in FQL. Let me demonstrate with the following example:
...ANSWER
Answered 2021-Oct-22 at 21:08When you set a key's value to null
in Fauna, it is removed from the object. In your example, assuming ref
is a valid Reference:
QUESTION
I'm don't understand how to unwind and then nested collections in mongoDB. basically I have two collections that are structured like this:
questions doc:
...ANSWER
Answered 2021-Mar-22 at 17:40UPDATE based on comments:
Updated query:
QUESTION
I'm struggling with this nested document too much. I tried to read the document and also follow other SO responses to see if it works for me, but I'm not getting the results that I'm looking for. I want to extract some information from a big nested document.
DATA
I've uploaded the data to mongo playground. https://mongoplayground.net/p/7nbLtXMlFMx
...ANSWER
Answered 2020-Oct-08 at 23:51You can do (almost!) anything with an aggregate query. In your case I suggest using $unwind
to convert the lists to onjects, then $match
on your target field(s), $project
to trim down the output, $replaceRoot
to simplify the structure and $limit
for good measure as there's actually 2 records that match your criteria.
QUESTION
Suppose I'm using the cursor to iterate a subset of the documents, ordered by some field let's say.
What happens if while iterating, a new document is being inserted or a current one is being deleted?
Would that affect the cursor or does it MongoDB make some sort of snapshot of the data?
...ANSWER
Answered 2020-Aug-15 at 22:20When you are in a transaction with read concern snapshot, you are reading from a consistent snapshot of the data.
Otherwise you could be experiencing various phenomena described here.
QUESTION
I would like to save a single document field into a local variable, but I am not able to do that. Here is my code:
...ANSWER
Answered 2020-Jul-11 at 21:57You should probably change
QUESTION
I am currently working on an ASP.Net application that stores student information. I am required to store the following information:
- Student number
- Name
- Email address
- Home address
- Contact no.
- Upload photo of the student
- isActive flag to state whether the student is active or not
This information is being stored in a document database and the photo of the student needs to be uploaded to Azure blob storage while returning the link of the image to the document database
How do I do this?
I currently have a class for the student information which looks like this :
...ANSWER
Answered 2020-Mar-10 at 14:52Using Azure CosmosDB for the storage could help. With CosmosDB, you can easily store the image as an attachment to the student document: https://docs.microsoft.com/en-us/rest/api/cosmos-db/attachments
If you don't plan to use CosmosDB, be more precise please about the database storage.
QUESTION
I am very confused between schema, model, instance of a model, and collection in Mongoose.
My understanding is as follows:
- Mongoose.schema( { } ) - analogous to defining the columns of a table in relational databases
- Mongoose.model( 'Name', Schema) - analogous to creating a table in relational dbs (create table statement)
- new Model ({ //DATA }) - analogous to creating a row in relational dbs
- new Model ().query() - analogous to query statements (general Query) in relational dbs
Is this correct?
...ANSWER
Answered 2020-Jan-18 at 19:54You are mostly correct.
Firstly MongoDB is unstructured by nature, hence i recommend not trying to find "analogies" to match it to the structured scheme. With that said similarities do exist so for simplicity we can do so.
One more note is that this syntax your referring to is mongoose
specifically and not the original Mongo
syntax.
Mongoose.schema( { } )
Yes, mongoose gives you the ability to "force" a structure, note this will only come into play when trying toinsert
/create
/update
documents and not when it comes to querying.Mongoose.model('Name', Schema)
Yes-ish, mongoose will not create a database per-se, meaning if it does not exist a new one will be created, however inserting a document to that model will create a such collection.new Model ({ //DATA })
Yes, however you need to addnew Model().save()
, without the save it will not be triggered and saved into the database.new Model ().query()
Yes-ish, again similar to themodel
function this is a mongoose wrapper (that I'm less familiar with) As specified in the docs:
Query constructor used for building queries. You do not need to instantiate a Query directly. Instead use Model functions like Model.find().
Personally I just use the Model functions to query such as find
,findOne
,aggregate
and more.
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