I have a large file contain > 10 million line. I want to get dupplicate line using MapReduce.
How can I solve this problem?
Thanks for help
You need to make use of the fact that the default behaviour of MapReduce is to group values based on a common key.
So the basic steps required are:
Read in each line of you file to you mapper, probably using something like the TextInputFormat.
Set the output Key (Text object) to the value of each line. The contents of the value doesn't really matter. You can just set it to a NullWritable if you want.
In the reduce check the number of values grouped for each key. If you have more than one value you know you have a duplicate.
If you just want the duplicate values, write out the keys that have multiple values.
Related
Is it possible to overwrite a record in the target if specific conditions are met using spark without reading the target into a dataframe? For example, I know we can do this if both sets of data are loaded into dataframes, but I would like to know if there is a way to perform this action without loading the target into a dataframe. Basically, a way to specify overwrite/update conditions.
I am guessing no, but I figured I would ask before I dive into this project. I know we have the write options of append and overwrite. What I really want is, if a few specific columns already exist in the data target, then overwrite it and fill in the other columns with the new data. For example:
File1:
id,name,date,score
1,John,"1-10-17",35
2,James,"1-11-17",43
File2:
id,name,date,score
3,Michael,"1-10-17",23
4,James,"1-11-17",56
5,James,"1-12-17",58
I would like the result to look like this:
id,name,date,score
1,John,"1-10-17",35
3,Michael,"1-10-17",23
4,James,"1-11-17",56
5,James,"1-12-17",58
Basically, Name and Date columns act like primary keys in this scenario. I want updates to occur based on those two columns matching, otherwise make a new record. As you can see id 4 overwrites id 2, but id 5 appends because the date column did not match. Thanks ahead guys!
I have this kind of data:
I need to transpose this data into something like this using Talend:
Help would be much appreciated.
dbh's suggestion should work indeed, but I did not try it.
However, I have another solution which doesn't require to change input format and is not too complicated to implement. Indeed the job has only 2 transformation components (tDenormalize and tMap).
The job looks like the following:
Explanation :
Your input is read from a CSV file (could be a database or any other kind of input)
tDenormalize component will Denormalize your column value (column 2), based on value on id column (column 1), separating fields with a specific delimiter (";" in my case), resulting as shown in 2 rows.
tMap : split the aggregated column into multiple columns, by using java's String.split() method and spreading the resulting array into multiple columns. The tMap should like like this:
Since Talend doesn't accept to store Array objects, make sure to store the splitted String in Object format. Then, cast that object into Array on the right side of the Map.
That approach should give you the expected result.
IMPORTANT:
tNormalize might shuffle the rows, meaning for bigger input, you might encounter unsorted output. Make sure to sort it if needed or use tDenormalizeSortedRow instead.
tNormalize is similar to an aggregation component meaning it scans the whole input before processing, which results into possible performance issues with particularly big inputs (tens of millions of records).
Your input is probably wrong (you have 5 entries with 1 as id, and 6 entries with 2 as id). 6 columns are expected meaning you should always have 6 lines per id. If not, then you should implement dbh's solution, and you probably HAVE TO add a column with a key.
You can use Talend's tPivotToColumnsDelimited component to achieve this. You will most likely need an additional column in your data to represent the field name.
Like "Identifier, field name, value "
Then you can use this component to pivot the data and write a file as output. If you need to process the data further, read the resulting file with tFileInoutDelimited .
See docs and an example at
https://help.talend.com/display/TalendOpenStudioComponentsReferenceGuide521EN/13.43+tPivotToColumnsDelimited
I am working on a database that (hopefully) will end up using a primary key with both numbers and letters in the values to track lots of agricultural product. Due to the way in which the weighing of product takes place at more than one facility, I have no other option but to maintain the same base number but use letters in addition to this base number to denote split portions of each lot of product. The problem is, after I create record number 99, the number 100 suddenly floats up and underneath 10. This makes it difficult to maintain consistency and forces me to replace this alphanumeric lot ID with a strictly numeric value in order to keep it sorted (which I use "autonumber" as the data type). Either way, I need the alphanumeric lot ID, and so having 2 ID's for the same lot can be confusing for anyone inputting values into the form. Is there a way around this that I am just not seeing?
If you're using query as a data source then you may try to sort it by string converted to number, something like
SELECT id, field1, field2, ..
ORDER BY CLng(YourAlphaNumericField)
Edit: you may also try Val function instead of CLng - it should not fail on non-numeric input
Why not properly format your key before saving ? e.g: "0000099". You will avoid a costly conversion later.
Alternatively, you could use 2 fields as the composite PK. One with the Number (as Long) and one with the Location (as String).
I have some content in a file on which I must generate statistics such as how many of records are of type - 1, type - 2 etc. Number of types can change and is unknown to the code until file arrives. In a SQL system, I can do this using COUNT and GROUP BY clause. But I am not sure if I can do this using SYNCSORT or COBOL program. Would anyone here have an idea on how I can implement 'GROUP BY' type query on a file using SYNCSORT.
Sample Data:
TYPE001 SUBTYPE001 TYPE01-DESC
TYPE001 SUBTYPE002 TYPE01-DESC
TYPE001 SUBTYPE003 TYPE01-DESC
TYPE002 SUBTYPE001 TYPE02-DESC
TYPE002 SUBTYPE004 TYPE02-DESC
TYPE002 SUBTYPE008 TYPE02-DESC
I want to get the information such as TYPE001 ==> 3 Records, TYPE002 ==> 3 Records. What the code doesn't know until runtime is the TYPENNN value
You show data already in sequence, so there is no need to sort the data itself, which makes SUM FIELDS= with SORT a poor solution if anyone suggests it (plus code for the formatting).
MERGE with a single input file and SUM FIELDS= would be better, but still require the code for formatting.
The simplest way to produce output which may suit you is to use OUTFIL reporting functions:
OPTION COPY
OUTFIL NODETAIL,
REMOVECC,
SECTIONS=(1,7,
TRAILER3=(1,7,
' ==> ',
COUNT=(M10,LENGTH=3),
' Records'))
The NODETAIL says "remove all the data lines". The REMOVECC says "although it is a report, don't use printer-control characters on position one of the output records". The SECTIONS says "we're going to use control-breaks, and here they (it in this case) are". In this case, your control-field is 1,7. The TRAILER3 defines the output which will be produced at each control-break: COUNT here is the number of records in that particular break. M10 is an editing mask which will change leading zeros to blanks. The LENGTH gives a length to the output of COUNT, three is chosen from your sample data with sub-types being unique and having three digits as the unique part of the data. Change to whatever suits your actual data.
You've not been clear, and perhaps you want the output "floating" (3bb instead of bb3, where b represents a blank)? That would require more code...
I have a Cassandra ColumnFamily (0.6.4) that will have new entries from users. I'd like to query Cassandra for those new entries so that I can process that data in another system.
My sense was that I could use a TimeUUIDType as the key for my entry, and then query on a KeyRange that starts either with "" as the startKey, or whatever the lastStartKey was. Is this the correct method?
How does get_range_slice actually create a range? Doesn't it have to know the data type of the key? There's no declaration of the data type of the key anywhere. In the storage_conf.xml file, you declare the type of the columns, but not of the keys. Is the key assumed to be of the same type as the columns? Or does it do some magic sniffing to guess?
I've also seen reference implementations where people store TimeUUIDType in columns. However, this seems to have scale issues as this particular key would then become "hot" since every change would have to update it.
Any pointers in this case would be appreciated.
When sorting data only the column-keys are important. The data stored is of no consequence neither is the auto-generated timestamp. The CompareWith attribute is important here. If you set CompareWith as UTF8Type then the keys will be interpreted as UTF8Types. If you set the CompareWith as TimeUUIDType then the keys are automatically interpreted as timestamps. You do not have to specify the data type. Look at the SlicePredicate and SliceRange definitions on this page http://wiki.apache.org/cassandra/API This is a good place to start. Also, you might find this article useful http://www.sodeso.nl/?p=80 In the third part or so he talks about slice ranging his queries and so on.
Doug,
Writing to a single column family can sometimes create a hot spot if you are using an Order-Preserving Partitioner, but not if you are using the default Random Partitioner (unless a subset of users create vastly more data than all other users!).
If you sorted your rows by time (using an Order-Preserving Partitioner) then you are probably even more likely to create hotspots, since you will be adding rows sequentially and a single node will be responsible for each range of the keyspace.
Columns and Keys can be of any type, since the row key is just the first column.
Virtually, the cluster is a circular hash key ring, and keys get hashed by the partitioner to get distributed around the cluster.
Beware of using dates as row keys however, since even the randomization of the default randompartitioner is limited and you could end up cluttering your data.
What's more, if that date is changing, you would have to delete the previous row since you can only do inserts in C*.
Here is what we know :
A slice range is a range of columns in a row with a start value and an end value, this is used mostly for wide rows as columns are ordered. Known column names defined in the CF are indexed however so they can be retrieved specifying names.
A key slice, is a key associated with the sliced column range as returned by Cassandra
The equivalent of a where clause uses secondary indexes, you may use inequality operators there, however there must be at least ONE equals clause in your statement (also see https://issues.apache.org/jira/browse/CASSANDRA-1599).
Using a key range is ineffective with a Random Partitionner as the MD5 hash of your key doesn't keep lexical ordering.
What you want to use is a Column Family based index using a Wide Row :
CompositeType(TimeUUID | UserID)
In order for this not to become hot, add a first meaningful key ("shard key") that would split the data accross nodes such as the user type or the region.
Having more data than necessary in Cassandra is not a problem, it's how it is designed, so what you must ask yourself is "what do I need to query" and then design a Column Family for it rather than trying to fit everything in one CF like you'd do in an RDBMS.