I am creating a program for a bar-code reader CHD FIVE running Windows CE 5.0.
i have a file containing a csv table output with item bar-codes(approx 94000 rows). It is 8MB in size. I can go through the file at every program startup but that is long. Maybe if i would serialize the data and after deserialization i get a DataTable. In what way could i do this? or any other ideas where a table such as this needs to be quickly accessible and searchable offline. i have searched for solutions bet havent found anything.
I would first sort the data and then use a quick search algorithm. You can create a parallel table with only the index and do the search on this table. You can also use a entropy minimization algorithm to create a new and simple index set.
Related
I currently have approximately 10M rows, ~50 columns in a table that I wrap up and share as a pivot. However, this also means that it takes approximately 30mins-1hour to download the csv or much longer to do a powerquery ODBC connection directly to Redshift.
So far the best solution I've found is to use Python -- Redshift_connector to run update queries and perform an unload a zipped resultset to an S3 bucket then use BOTO3/gzip to download and unzip the file, then finally performing a refresh from the CSV. This resulted in a 600MB excel file compiled in ~15-20 mins.
However, this process still feel clunky and sharing a 600MB excel file among teams isn't the best either. I've searched for several days but I'm not closer to finding an alternative: What would you use if you had to share a drillable table/pivot among a team with a 10GB datastore?
As a last note: I thought about programming a couple of PHP scripts, but my office doesn't have the infrastructure to support that.
Any help would or ideas would be most appreciated!
Call a meeting with the team and let them know about the constraints, you will get some suggestions and you can give some suggestions
Suggestions from my side:
For the file part
reduce the data, for example if it is time dependent, increase the interval time, for example an hourly data can be reduced to daily data
if the data is related to some groups you can divide the file into different parts each file belonging to each group
or send them only the final reports and numbers they require, don't send them full data.
For a fully functional app:
you can buy a desktop PC (if budget is a constraint buy a used one or use any desktop laptop from old inventory) and create a PHP/Python web application that can do all the steps automatically
create a local database and link it with the application
create the charting, pivoting etc modules on that application, and remove the excel altogether from your process
you can even use some pre build applications for charting and pivoting part, Oracle APEX is one examples that can be used.
A very simple question...
I have downloaded a very large .csv file (around 3.7 GB) and now wish to open it; but excel can't seem to manage this.
Please how do I open this file?
Clearly I am missing a trick!
Please help!
There are a number of other Stackoverflow questions addressing this problem, such as:
Excel CSV. file with more than 1,048,576 rows of data
The bottom line is that you're getting into database territory with that sort of size. The best solution I've found is Bigquery from Google's cloud platform. It's super cheap, astonishingly fast, and it automatically detects schemas on most CSVs. The downside is you'll have to learn SQL to do even the simplest things with the data.
Can you not tell excel to only "open" the file with the first 10 lines ...
This would allow you to inspect the format and then use some database functions on the contents.
Another thing that can impact whether you can open a large Excel file is the resources and capacity of the computer. That's a huge file and you have to have a lot of on-disk swap space (page file in windows terms) + memory to open a file of that size. So, one thing you can do is find another computer that has more memory and resources or increase your swap space on your computer. If you have windows just google how to increase your page file.
This is a common problem. The typical solutions are
Insert your .CSV file into a SQL database such as MySQL, PostgreSQL etc.
Processing you data using Python, or R.
Find a data hub for your data. For example, Acho Studio.
The problem with solution one is that you'll have to design a table schema and find a server to host the database. Also you need to write server side code to maintain or change the database. The problem with Python or R is that running processes on GBs of data will put a of stress to your local computer. A data hub is much easier but its costs may vary.
I am trying to learn SQLyog Job Agent (SJA).
I am on a Linux machine, and use SJA from within a bash script by a line command: ./sja myschema.xml
I need to sync an almost 100 tables db and its local clone.
Since a single table stores a few config data, which I do not wish to sync, it seems I need to write a myschema.xml where I list all the remaining 99 tables.
Question is: is there a way to write to sync all the table but a single one?
I hope my question is clear. I appreciate your help.
If you are using the latest version of sqlyog:You are given the table below, and the option to generate an xml job file at the end of the database syncronisation wizard reflecting the operation you've opted to perform. This will in effect list the other 99 tables in the xml file itself for you, but it will give you what you are looking for, and I dont think you would be doing anything in particular with an individual table, since you are specifying all tables in a single element.
I wrote a Console Application that reads list of flat files
and Parse the data type on a row basis
and inserts records one after other in respective tables.
there are few Flat Files which contains about 63k records(rows).
for such files, my program is taking about 6 hours for one file of 63k
records to complete.
This is a test data file. In production i have to deal with 100 time more load.
I am worried, if i can do this any better to speed up.
Can any one suggest a best way to handle this job?
Work Flow is as below:
Read the FlatFile from Local Machine using File.ReadAllLines("location")
Create a Record Entity object after parsing each field of the row.
Insert this current row in to the Entity
Purpose of making this as console application is,
this application should be run(scheduled application) on weekly basis
and there is conditional logic in it, based on some variable there will be
full table replace or
update a existing table or
delete records in table.
You can try to use 'bulk insert' operation for inserting a huge data into database.
I have been working with databases recently and before that I was developing standalone components that do not use databases.
With all the DB work I have a few questions that sprang up.
Why is a database query faster than a programming language data retrieval from a file.
To elaborate my question further -
Assume I have a table called Employee, with fields Name, ID, DOB, Email and Sex. For reasons of simplicity we will also assume they are all strings of fixed length and they do not have any indexes or primary keys or any other constraints.
Imagine we have 1 million rows of data in the table. At the end of the day this table is going to be stored somewhere on the disk. When I write a query Select Name,ID from Employee where DOB="12/12/1985", the DBMS picks up the data from the file, processes it, filters it and gives me a result which is a subset of the 1 million rows of data.
Now, assume I store the same 1 million rows in a flat file, each field similarly being fixed length string for simplicity. The data is available on a file in the disk.
When I write a program in C++ or C or C# or Java and do the same task of finding the Name and ID where DOB="12/12/1985", I will read the file record by record and check for each row of data if the DOB="12/12/1985", if it matches then I store present the row to the user.
This way of doing it by a program is too slow when compared to the speed at which a SQL query returns the results.
I assume the DBMS is also written in some programming language and there is also an additional overhead of parsing the query and what not.
So what happens in a DBMS that makes it faster to retrieve data than through a programming language?
If this question is inappropriate on this forum, please delete but do provide me some pointers where I may find an answer.
I use SQL Server if that is of any help.
Why is a database query faster than a programming language data retrieval from a file
That depends on many things - network latency and disk seek speeds being two of the important ones. Sometimes it is faster to read from a file.
In your description of finding a row within a million rows, a database will normally be faster than seeking in a file because it employs indexing on the data.
If you pre-process you data file and provided index files for the different fields, you could speedup data lookup from the filesystem as well.
Note: databases are normally used not for this feature, but because they are ACID compliant and therefore are suitable for working in environments where you have multiple processes (normally many clients on many computers) querying the database at the time.
There are lots of techniques to speed up various kinds of access. As #Oded says, indexing is the big solution to your specific example: if the database has been set up to maintain an index by date, it can go directly to the entries for that date, instead of reading through the entire file. (Note that maintaining an index does take up space and time, though -- it's not free!)
On the other hand, if such an index has not been set up, and the database has not been stored in date order, then a query by date will need to go through the entire database, just like your flat-file program.
Of course, you can write your own programs to maintain and use a date index for your file, which will speed up date queries just like a database. And, you might find that you want to add other indices, to speed up other kinds of queries -- or remove an index that turns out to use more resources than it is worth.
Eventually, managing all the features you've added to your file manager may become a complex task; you may want to store this kind of configuration in its own file, rather than hard-coding it into your program. At the minimum, you'll need features to make sure that changing your configuration will not corrupt your file...
In other words, you will have written your own database.
...an old one, I know... just for if somebody finds this: The question contained "assume ... do not have any indexes"
...so the question was about the sequential dataread fight between the database and a flat file WITHOUT indexes, which the database wins...
And the answer is: if you read record by record from disk you do lots of disk seeking, which is expensive performance wise. A database always loads pages by concept - so a couple of records all at once. Less disk seeking is definitely faster. If you would do a mem buffered read from a flat file you could achieve the same or better read values.