SimpleDB | SimpleDB implementation for MIT | Database library
kandi X-RAY | SimpleDB Summary
kandi X-RAY | SimpleDB Summary
This is an implementation of SimpleDB as part of the MIT 6.830 Database Systems course on MIT OpenCourseware. The course consists of the following labs, which implement major components of a relational database:. Lab1: Buffer pool and heap files. Lab2: Operators such as join, filter, aggregates, inserts, etc. Lab3: Transactions via a Lock Manager. Lab5: Rollback and recovery.
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- The main entry point for the script
- Displays the join plan
- Computes the cost and cardinality of joins
- Converts a logical plan to a DbIterator
- Main entry point
- Convert a list of integers to a string
- Convert a text file into a binary page
- Recover the database system
- Read PageData from the Reader
- Compares a field with the given operator
- Generate a logical plan from a string
- Reads the next tuples from the child operator
- Creates a TupleDesc with the fields of the file
- Compute the min and max of the fields in the table
- Takes a list of tuples and returns a tuple of the width of each field
- Reads the next tuple produced by the join predicate
- Deletes the next tuple from the child operator
- Reads the next tuple in the table
- Read a page of data from disk
- Prints the log
- Add a tuple of tuples to the buffer
- Read the next tuple from the source file
- Create a new empty table with the given columns
- Return a DbIterator for the group aggregate results
- Generate histograms
- Creates a DbIterator for the aggregate results
SimpleDB Key Features
SimpleDB Examples and Code Snippets
Community Discussions
Trending Discussions on SimpleDB
QUESTION
...
ANSWER
Answered 2021-Jun-25 at 18:55add a User
property to your App
class
QUESTION
I read this answer, which clarified a lot of things, but I'm still confused about how I should go about designing my primary key.
First off I want to clarify the idea of WCUs. I get that WCU is the write capacity of max 1kb per second. Does it mean that if writing a piece of data takes 0.25 seconds, I would need 4 of those to be billed 1 WCU? Or each time I write something it consumes 1 WCU, but I could also write X times within 1 second and still be billed 1 WCU?
Usage
I want to create a table that stores the form data for a set of gyms (95% will be waivers, the rest will be incidents reports). Most of the time, each forms will be accessed directly via its unique ID. I also want to query the forms by date, form, userId, etc..
We can assume an average of 50k forms per gym
Options
First option is straight forward: having the formId be the partition key. What I don't like about this option is that scan operations will always filter out 90% of the data (i.e. the forms from other gyms), which isn't good for RCUs.
Second option is that I would make the gymId the partition key, and add a sort key for the date, formId, userId. To implement this option I would need to know more about the implications of having 50k records on one partition key.
Third option is to have one table per gyms and have the formId as partition key. This seems to be like the best option for now, but I don't really like the idea of having a a large number of tables doing the same thing in my account.
Is there another option? Which one of the three is better?
Edit: I'm assuming another option would be SimpleDB?
...ANSWER
Answered 2021-May-21 at 20:26For your PK design. What data does the app have when a user is going to look for a form? Does it have the GymID, userID, and formID? If so, make a compound key out of that for the PK perhaps? So your PK might look like:
QUESTION
I have the following requirements:
- For every deleted record in RDS we need to archive it into somewhere cheaper on AWS.
- Reduce storage cost
- Not using Glacier
- Context oriented (e.g. a file per table)
- re-import is not a requirement
I'm not an experienced user with AWS, so I'm still a bit lost among the amount of options it has to offer and I'd like to know if you have more ideas to help me clear it out.
Initial thoughts:
- The microservice that deletes the record, might send it to a broker (RabbitMQ for e.g.) and another microservice (let's call it
archiver
) will listen to it, write into a file, zip and send to S3. This approach has some technical challenges though: in order to make sense create big files, I need to wait the queue to growth a bit, wrap it into a stream and zip inside S3. The transaction control is very weak as well, since file writing and ack on messages are signal based i.e. I'll remove the messages from the broker just after the file is created. - Add a new column to the "archiveble" tables as "deleted (bool)" and run a separate job fetching only those records and saving them into S3. Discarded they don't want the new microservice with access to other's databases.
- Following the same approach as in the first item, but instead of save into S3, save into a cheaper database. SimpleDB?
ANSWER
Answered 2020-Jul-03 at 16:54option 1, but instead of rabbitmq, write it to a kinesis firehose and direct that to an s3 location - it doesn't get much cheaper or easier than that.
QUESTION
I have tried all of the solutions I could find and still haven't been able to get around this error. The error occurs in the getNotes() section, in its forth line. Also, the getNote() is currently not doing anything, so you don't need to look at that. I directly copied all code from these youtube tutorials, which I then adapted to my needs.
https://www.youtube.com/watch?v=pa_lghjVQVA&t=933s
...Thanks for any help.
ANSWER
Answered 2020-Apr-23 at 23:03I assume that you had been following the video which builds up the Database handling step by step.
I have taken your code, added a Note class so it will compile and played around with it a bit. The code itself works fine, however you had (probably do to incremental changes of the code) deleted the table and it has not been recreated yet. Therefore it will always lead to a crash.
Fortunately this can be solved very easily by:
- Either reinstalling the App
- Or by incrementing the Database version
If you choose to delete and install the App again, you can reset the Database version to 1.
If you choose to increment the Database version, onUpgrade
will be called which will delete the table (if it exists) and then recreate it (by calling onCreate
).
As someone already mentioned as a comment, SQL should be handled on Android by using Room
nowadays. I understand you are probably just starting out, but once you get better you should definitely check out Room. It makes things a LOT easier.
Hope this solves your issue :)
Community Discussions, Code Snippets contain sources that include Stack Exchange Network
Vulnerabilities
No vulnerabilities reported
Install SimpleDB
You can use SimpleDB like any standard Java library. Please include the the jar files in your classpath. You can also use any IDE and you can run and debug the SimpleDB component as you would do with any other Java program. Best practice is to use a build tool that supports dependency management such as Maven or Gradle. For Maven installation, please refer maven.apache.org. For Gradle installation, please refer gradle.org .
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