I am developing an application of iphone which is navigation based, and i am showing data on first View Items then on second View Sub Items and so on. So my question is that what will good approach to save this on Data base (sqlite).
Keep this simple.
Each object/View has it's own ID and at least one parent ID.
This will ensure your data can represent trees of any depth and any complexity.
i am not an expert in this field but you can do it like this ... now that you said all you data can be represented something like tree...
Find all the objects that will be leaf of your tree make those objects as a table in DB, (please keep in mind that you make table only for objects that have different structure not because they have different values)
Repeat above step for one level above until you reach top
Eventually you will find that you just got your DB.
To be more precise you need to study DBMS
Related
I have a situation as described in the ExtbaseFluid book:
I would like to store information in the intermediate table which is not recommended at all.
Here is a cite from the warning box of the above linked book chapter:
Do not store data in the Intermediate Table that concern the Domain. Though TYPO3 supports this (especially in combination with Inline Relational Record Editing (IRRE) but this is always a sign that further improvements can be made to your Domain Model. Intermediate Tables are and should always be tools for storing relationships and nothing else.
Let’s say you want to store a CD with its containing music tracks: CD -- m:n (Intermediate Table) -- Song. The track number may be stored in a field of the Intermediate Table. However, the track should be stored as a separate domain object, and the connection be realized as CD -- 1:n -- Track -- n:1 -- Song.
So I want not to do what is not recommended. But thinking about the workflow for the editor that results of the recommended solution rises a few question for me.
To stay with this example I would need the following tables:
tx_extname_domain_model_cd
tx_extname_domain_model_cd_track_mm
tx_extname_domain_model_track (which holds the track number)
tx_extname_domain_model_track_song_mm
tx_extname_domain_model_song
From what I know this would end in the situation that the editor would need to create following records:
one record for the cd
one record for the song
now the editor can create one record for the track.
There the track number is added.
Furthermore the cd record needs to be assigned as well as the song.
So here are my questions:
I guess this workflow cannot be improved with some (to me unknown) TCA setup?
An editor cannot directly reach the song when the cd record is opened?
Instead first she / he has to open the track record and can from there navigate to the song?
Is it really that bad to store data in the intermediate table? The TYPO3 table sys_file_reference does the same!? But I wonder how those data could be shown (because IRRE is not possible because it shall only be used for 1:n relations (source).
The question you have to ask yourself is: Do I want to do coding by the book, or do I want to create a pragmatic approach to solve a customer's problem?
In this specific case the additional problem is, that the people who originally invented Extbase had a quite sophisticated and academic approach, but when it comes to a pragmatic use and performance, they were blocked by their own rules and stuck with coding by the book.
Especially this example and the warning message shows a way of thinking that was one of the reasons, why I never actually used Extbase but went for Core-API methods to create performant and pragmatic queries to get the desired result sets. Now that we've got Doctrine under the hood, this works like a charm even with quite exotic DB flavors.
Of course intermediate tables are a good idea and of course those intermediate tables can and should be enriched with additional data fields, that do not require a 3rd, 4th or nth table to store i.e. a simple set of dropdown options, since this can easily be handled with attributes configured in TCA, as it is shown here: https://docs.typo3.org/m/typo3/reference-tca/master/en-us/ColumnsConfig/Type/Inline/Examples.html
sys_file_reference is the most prominent example since it provides exactly that kind of additional information that should not be pumped into additional tables - and guess what, the TYPO3 core does not make use of a single line of Extbase code to deal with that data or almost any other data of the core tables.
To answer your last question: Take a look at the good old IRRE Tutorial to get a clue how to do m:n connections with intermediate inline tables.
https://docs.typo3.org/typo3cms/extensions/irre_tutorial/0.4.0/Manual/Index.html#intermediate-tables-for-m-n-relations
Depends on the issue, sometimes the intermediate table is an entity, sometimes not. In this example the intermediate table is the track, which would contain: [uid, cd, song, track_no, ... (whatever else needed to define the track)]
Be carefull when you define your data, that you do not make it too advanced.
I have a database of million of Objects (simply say lot of objects). Everyday i will present to my users 3 selected objects, and like with tinder they can swipe left to say they don't like or swipe right to say they like it.
I select each objects based on their location (more closest to the user are selected first) and also based on few user settings.
I m under mongoDB.
now the problem, how to implement the database in the way it's can provide fastly everyday a selection of object to show to the end user (and skip all the object he already swipe).
Well, considering you have made your choice of using MongoDB, you will have to maintain multiple collections. One is your main collection, and you will have to maintain user specific collections which hold user data, say the document ids the user has swiped. Then, when you want to fetch data, you might want to do a setDifference aggregation. SetDifference does this:
Takes two sets and returns an array containing the elements that only
exist in the first set; i.e. performs a relative complement of the
second set relative to the first.
Now how performant this is would depend on the size of your sets and the overall scale.
EDIT
I agree with your comment that this is not a scalable solution.
Solution 2:
One solution I could think of is to use a graph based solution, like Neo4j. You could represent all your 1M objects and all your user objects as nodes and have relationships between users and objects that he has swiped. Your query would be to return a list of all objects the user is not connected to.
You cannot shard a graph, which brings up scaling challenges. Graph based solutions require that the entire graph be in memory. So the feasibility of this solution depends on you.
Solution 3:
Use MySQL. Have 2 tables, one being the objects table and the other being (uid-viewed_object) mapping. A join would solve your problem. Joins work well for the longest time, till you hit a scale. So I don't think is a bad starting point.
Solution 4:
Use Bloom filters. Your problem eventually boils down to a set membership problem. Give a set of ids, check if its part of another set. A Bloom filter is a probabilistic data structure which answers set membership. They are super small and super efficient. But ya, its probabilistic though, false negatives will never happen, but false positives can. So thats a trade off. Check out this for how its used : http://blog.vawter.com/2016/03/17/Using-Bloomfilters-to-Avoid-Repetition/
Ill update the answer if I can think of something else.
I've got a question for you couchbase pros: Is it possible to synchronize a subset of documents (eg. the documents within a view) with an other bucket?
So that the other bucket documents are always a direct subset of the "master" bucket?
if so, isn't that to much expensive in terms of perfomance? or does couchbase have any functionality to only create deeplinks to the documents instead of copying it?
Alternatively: is it possible to write views on views?
Thank you in advance!
--- EDIT ----
Let's say I want to have two sets (buckets) of documents S1 and S2. S2 is a subset of S1. Each set contains the same views V1, V2 and V3 since I want to be able to query any of them with the same logic/interface. In my case set S2 is build per user/company/store/whatever, in production there should be like 1000ish subsets S2 - to stay abstract let's call them S2a S2b and S2c.
The selection of documents which to be contained in any subset is done by a filtering instance (for example a view). Let's call these filtering instances F1 for filtering S1 to S2 hence F1a, F1b and F1c.
So with my actual knowledge of couchbase this results in the following design/view architecture: I've got the three "base" views to display V1,V2 and V3, and to realize S2a, S2b and S2c I must create the design views S2aV1, S2aV2, S2aV3, S2bV1, S2bV2, etc. (9 Views).
One could say "Well choose your keys wisely and you can avoid the sub views" but in my opinion this isn't that easy because of the following circumstances: In worst case the filter parameters change every minute and contain many WHERE IN constraints which could (at my actual point of view) not be handled efficiently querying k/v lists.
This leads to the following thoughts and the question I initially asked. If I use the same views in any subset (defined by a filter) shouldn't it be possible to build up an entity which helps me handling complex filtering? For example a function which is called during runtime while generating the view output? This could look like /design/view?filter=F1 or something like that.
Or do you have any other ideas to solve this problem? Or should I use SQL since it's more capable of handling frequently changing filters?
Generally speaking for most models you don't really need to have bucket "subsets", is there a particular reason you are trying to do this and why you would want that data broken out? You can also query your views, or instead of a view on a view, you can just make a separate view that maps/filters further based on your needs (i.e. does the same job as a view on a view).
We are working on Elastic Search integration. Maybe better for your use case
I think what you want to do is write a view on your original bucket, and then copy the key/values from that view, to be documents in a new bucket.
It shouldn't be hard to write an automated framework for managing this so that you can keep the derived data up to date in near real time.
I have a Triangle class. Each Triangle has three edges a, b, and c, and also three angles angleA, angleB, and angleC. In addition to the size (length or angle), each datum also stores whether it was entered by the user or was calculated based on geometric relationships to other data.
Corresponding to my Triangle class, I have a TriangleSidesAndAnglesView. This view has six subviews -- one for each of the angles, and one for each of the sides. The contents of the subviews depends on the information in the model class. The subviews are all of class TriangleDatumView.
Information can pass both ways. For example, if the user enters something in a text field corresponding to an edge or angle, the entered value needs to be passed up to the model.
I am trying to figure out how to keep everything organized. For example, should the TriangleDatumView objects contain references to the respective corresponding members in the model class? Does the TriangleSidesAndAnglesView need to keep a table of which TriangleDatumView corresponds to what model object? Should the TriangleDatumView for (say) edge b know that the name of the edge it is displaying is "b" so that it can write "b=" each time . . . or does it grab that info from the model?
Nothing here is fundamentally difficult. The challenge is organizing it all in a sensible way.
Thanks for any help.
A question I ask myself is "What do I want to be able to independently vary?" -- meaning, if I have a model, could I imagine a totally different implementation of the same interface or a totally different view for the same model. In the variations that I care about, what needs to be where.
So, if labels are always A, B, and C -- I see no reason to store labels in the model. If they can change, then yes, you should not hard-code them in the view.
Views in MVC often have references right to the model they are viewing. Sometimes the controller is an intermediary. Models should usually not contain references to views -- but instead use things like delegates to alert of changes to their state.
I'm in the "Do the simplest thing that works, and don't repeat yourself, refactor when necessary" camp. The issue with building in the complexity at the start is that it might be complex on the wrong axis -- let the features dictate how the interfaces grow.
A view controller could sit between model and view, managing an array of TriangleView instances. The controller adds, modifies and deletes views based on what is in the model, and does the same for model instances based upon changes to the parent view (typing in a text field, tapping and dragging, and other UI actions, etc.).
What are some possible designs to deal with frequently changing data forms?
I have a basic CRUD web application where the main data entry form changes yearly. So each record should be tied to a specific version of the form. This requirement is kind of new, so the existing application was not built with this in mind.
I'm looking for different ways of handling this, hoping to avoid future technical debt. Here are some options I've come up with:
Create a new object, UI and set of tables for each version. This is obviously the most naive approach.
Keep adding all the fields to the same object and DB tables, but show/hide them based on the form version. This will become a mess after a few changes.
Build form definitions, then dynamically build the UI and store the data as some dictionary like format (e.g. JSON/XML or maybe an document oriented database) I think this is going to be too complex for the scope of this app, especially for the UI.
What other possibilities are there? Does anyone have experience doing this? I'm looking for some design patterns to help deal with the complexity.
First, I will speak to your solutions above and then I will give my answer.
Creating a new table for each
version is going to require new
programming every year since you will
not be able to dynamically join to
the new table and include the new
columns easily. That seems pretty obvious and really makes this a bad choice.
The issues you mentioned with adding
the columns to the same form are
correct. Also, whatever database you
are using has a max on how many
columns it can handle and how many
bytes it can have in a row. That could become another concern.
The third option I think is the
closest to what you want. I would
not store the new column data in a
JSON/XML unless it is for duplication
to increase speed. I think this is
your best option
The only option you didn't mention
was storing all of the data in 1
database field and using XML to
parse. This option would make it
tough to query and write reports
against.
If I had to do this:
The first table would have the
columns ID (seeded), Name,
InputType, CreateDate,
ExpirationDate, and CssClass. I
would call it tbInputs.
The second table would have the have
5 columns, ID, Input_ID (with FK to
tbInputs.ID), Entry_ID (with FK to
the main/original table) value, and
CreateDate. The FK to the
main/original table would allow you
to find what items were attached to
what form entry. I would call this
table tbInputValues.
If you don't
plan on having that base table then
I would use a simply table that tracks the creation date, creator ID,
and the form_id.
Once you have those you will just need to create a dynamic form that pulls back all of the inputs that are currently active and display them. I would put all of the dynamic controls inside of some kind of container like a <div> since it will allow you to loop through them without knowing the name of every element. Then insert into tbInputValues the ID of the input and its value.
Create a form to add or remove an
input. This would mean you would
not have much if any maintenance
work to do each year.
I think this solution may not seem like the most eloquent but if executed correctly I do think it is your most flexible solution that requires the least amount of technical debt.
I think the third approach (XML) is the most flexible. A simple XML structure is generated very fast and can be easily versioned and validated against an XSD.
You'd have a table holding the XML in one column and the year/version this xml applies to.
Generating UI code based on the schema is basically a bad idea. If you do not require extensive validation, you can opt for a simple editable table.
If you need a custom form every year, I'd look at it as kind of a job guarantee :-) It's important to make the versioning mechanism and extension transparent and explicit though.
For this particular app, we decided to deal with the problem as if there was one form that continuously grows. Due to the nature of the form this seemed more natural than more explicit separation. We will have a mapping of year->field for parts of the application that do need to know which data is for which year.
For the UI, we will be creating a new page for each year's form. Dynamic form creation is far too complex in this situation.