I have multiple csv file with difference header tile, and I want to merge all of them & keep combination Header title.
I think I can doing cover csv to array then compare header tile in all file then merge csv file. However, seem it get huge processing time because o a lot of loop there. Could you help if have any fast solution.
Example:
file1.csv
No,Series,Product,A,B,C,D,E
1, AAA, XX, a1,b1,c1,d1,e1
file2.csv
No,Series,Product,A,C,D,B,E,F,G
1, AAB, XX, a1,c1,d1,b1,e1,f1,g1
file3.csv
No,Series,Product,A,A1,A2,C,D,B1,B,E
1, AAC, XX, a1,a11,a21,c1,d1,b11,b1,e1
My expected merge file is:
merge.csv
No,Series,Product,A,A1,A2,B,B1,C,D,E,F,G
1, AAA, XX, a1,0,0,b1,0,c1,d1
1, AAB, XX, a1,0,0,b1,0,c1,d1,e1,f1,g1
1, AAC, XX, a1,a11,a21,b1,b11,c1,d1,e1
"Data which not available in column will show as "0" or "NA",etc.
From your comment it seems you have no code but you think your sketch will be slow, it sounds like you are optimising prematurely – code your algorithm, test it, if its slow use Instruments to see where the time is being spent and then look at optimisation.
That said some suggestions:
You need to decide if you are supporting general CSV files, where field values may contain commas, newlines or double quotes; or simple CSV files where none of those characters is present in a field. See section 2 of Common Format and MIME Type for Comma-Separated Values (CSV) Files what what you need to parse to support general CSV files, and remember you need to output values using the same convention. If you stick with simple CSV files then NSString's componentsSeparatedByString: and NSArray's componentsJoinedByString: may be all you need to parse and output respectively.
Consider first iterating over your files reading just the header rows, parse those, and produce the merged list of headers. You will need to preserve the order of the headers, so you can pair them up with the data rows, so arrays are your container of choice here. You may choose to use sets in the merging process, but the final merged list of headers should also be an array in the order you wish them to appear in the merged file. You can use these arrays of headers directly in the dictionary methods below.
Using a dictionary as in your outline is one approach. In this case look at NSDictionary's dictionaryWithObjects:forKeys: for building the dictionary from the parsed header and record. For outputting the dictionary look at objectsForKeys:notFoundMarker: and using the merged list of headers. This supports missing keys and you supply the value to insert. For standard CSV's the missing value is empty (i.e. two adjacent commas in the text) but you can use NA or 0 as you suggest.
You can process each file in turn, a row at a time: read, parse, make dictionary, get an array of values back from dictionary with the missing value in the appropriate places, combine, write. You never need to hold a complete file in memory at any time.
If after implementing your code using dictionaries to easily handle the missing columns you find it is too slow you can then look at optimising. You might want to consider instead of breaking each input data row into fields and the recombining adding in the missing columns that you just do direct string replacement operations on the text of the data row and just add in extra delimiters as needed – e.g. if column four is missing you can change the third comma for two commas to insert the missing column.
If after designing your algorithm and coding it you hit problems you can ask a new question, include your algorithm and code, a link back to this question so people can follow the history, and explain what your issue is. Someone will undoubtedly help you take the next step.
HTH
I have data something like this in CSV file:
1|abc|"Hello,
how are you"|pqr
2|xyz|I am fine|tuv
3|hjd|what abt you|klf
You can see we have a multiline record in CSV.Although I can load this in hive table. But it will not show me the correct result.
How can I handle multiline records to load in hive
Hive is suitable for structured dataset, where the column sequence and delimiters are well defined. In your case, the EOL character is row delimiter and can occur in the dataset as well. Due to this, the data is semi structured.
You have few options:
If the file is being generated by any other program, you should
change the row delimiter to something else than a newline. The best
practice is to use Ctrl+A for column delimiter and Ctrl+B for row delimiter.
If option 1 is not feasible, Write a map-reduce with custom record reader implementation, where record reader could determine the boundary of one record (i.e. logic to pick one complete record). Reformat the record in the map reduce program to output records delimited with Ctrl+A (columns delimiter) and Ctrl+B (row delimiter). Now, you may load the file in hive.
I have a lengthy (with about 1000 characters) clob object stored in a table. I need to read this value through a bash script. How can I do this?
I've tried using a normal SELECT query. But then the output comes as multiple lines. I cannot merge them as it does not produce the exact text in the database in special cases (e.g. if there is a space at the end of single line)
e.g.
abcd
efg
hijk
If I merged the lines with sed ':a;N;$!ba;s/\n//g;', this becomes abcdefghijk when the actual text is abcdefg hijk.
What is the best approach for doing what I'm trying to do here.
Since I couldn't find a way around using the above method, I managed to do what I want using a different approach.
Since the space character was the problem, and since I am the one who is inserting those clobs, instead of inserting the text directly, I've first base64 encoded the text and inserted the encoded text into the table.
I could use the same SELECT query after this. I had to perform a base64 decode on the select output to get the original text.
I've been given some csv files that I want to turn into tables in a SQL database. However, the genius who created the files used comma delimiters, even though several data fields contain commas. So when I try to BCP the data into the database, I get a whole bunch of errors.
Is there a way that I can escape the commas that aren't field separators? At the moment I'm tempted to write a script to manually replace every comma in each file with a pipe, and then go through and manually change the affected rows back.
The only way to fix this is to write a script or program that fixes the data.
If the bad data is limited to a single field the process should be trivial:
You consume the row from either side by the count of good delimiters and replace with a new unique delimiter and what remains is the column with the extra old delimiters that you would just leave as is.
If you have two bad fields straddling good fields, you would need some kind of advanced logic, for instance I had XML data with delimiters, I had to parse the XML until I found a terminating tag and then process the other delimiters as needed.
I'm generating a CSV which contains several rows and columns.
However, when I'm testing said CSV I feel like I am simply repeating the code that builds the file in the test as I'm checking each and every field is correct.
Question is, is this more sensible than it seems to me, or is there a better way?
A far simpler test is to just import the CSV into a spreadsheet or database and verify the data output is aligned to the proper fields. No extra columns or extra rows, data selected from the imported recordset is a perfect INTERSECT with the recordset from which the CSV was generated, etc.
More importantly, I recommend making sure your test data includes common CSV fail scenarios such as:
Field contains a comma (or whatever your separator character)
Field contains multiple commas (You might think it's the same thing, but I've seen one fail where the other succeeded)
Field contains the new-row character(s)
Field contains characters not in the code page of the CSV file
...to make sure your code is handling them properly.