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 package org.apache.pig;
 
 
 
StoreFuncs take records from Pig's processing and store them into a data store. Most frequently this is an HDFS file, but it could also be an HBase instance, RDBMS, etc.
 
 public interface StoreFuncInterface {

    
This method is called by the Pig runtime in the front end to convert the output location to an absolute path if the location is relative. The StoreFuncInterface implementation is free to choose how it converts a relative location to an absolute location since this may depend on what the location string represent (hdfs path or some other data source). The static method LoadFunc.getAbsolutePath(java.lang.String,org.apache.hadoop.fs.Path) provides a default implementation for hdfs and hadoop local file system and it can be used to implement this method.

Parameters:
location location as provided in the "store" statement of the script
curDir the current working direction based on any "cd" statements in the script before the "store" statement. If there are no "cd" statements in the script, this would be the home directory -
/user/<username> 
Returns:
the absolute location based on the arguments passed
Throws:
java.io.IOException if the conversion is not possible
 
     String relToAbsPathForStoreLocation(String locationPath curDirthrows IOException;

    
Return the OutputFormat associated with StoreFuncInterface. This will be called on the front end during planning and on the backend during execution.

Returns:
the org.apache.hadoop.mapreduce.OutputFormat associated with StoreFuncInterface
Throws:
java.io.IOException if an exception occurs while constructing the OutputFormat
 
     OutputFormat getOutputFormat() throws IOException;

    
Communicate to the storer the location where the data needs to be stored. The location string passed to the StoreFuncInterface here is the return value of relToAbsPathForStoreLocation(java.lang.String,org.apache.hadoop.fs.Path) This method will be called in the frontend and backend multiple times. Implementations should bear in mind that this method is called multiple times and should ensure there are no inconsistent side effects due to the multiple calls. checkSchema(org.apache.pig.ResourceSchema) will be called before any call to setStoreLocation(java.lang.String,org.apache.hadoop.mapreduce.Job).

Parameters:
location Location returned by relToAbsPathForStoreLocation(java.lang.String,org.apache.hadoop.fs.Path)
job The org.apache.hadoop.mapreduce.Job object
Throws:
java.io.IOException if the location is not valid.
 
     void setStoreLocation(String locationJob jobthrows IOException;
 
    
Set the schema for data to be stored. This will be called on the front end during planning if the store is associated with a schema. A Store function should implement this function to check that a given schema is acceptable to it. For example, it can check that the correct partition keys are included; a storage function to be written directly to an OutputFormat can make sure the schema will translate in a well defined way.

Parameters:
s to be checked
Throws:
java.io.IOException if this schema is not acceptable. It should include a detailed error message indicating what is wrong with the schema.
    void checkSchema(ResourceSchema sthrows IOException;

    
Initialize StoreFuncInterface to write data. This will be called during execution before the call to putNext.

Parameters:
writer RecordWriter to use.
Throws:
java.io.IOException if an exception occurs during initialization
    void prepareToWrite(RecordWriter writerthrows IOException;

    
Write a tuple to the data store.

Parameters:
t the tuple to store.
Throws:
java.io.IOException if an exception occurs during the write
    void putNext(Tuple tthrows IOException;
    
    
This method will be called by Pig both in the front end and back end to pass a unique signature to the StoreFuncInterface which it can use to store information in the org.apache.pig.impl.util.UDFContext which it needs to store between various method invocations in the front end and back end. This is necessary because in a Pig Latin script with multiple stores, the different instances of store functions need to be able to find their (and only their) data in the UDFContext object.

Parameters:
signature a unique signature to identify this StoreFuncInterface
    public void setStoreFuncUDFContextSignature(String signature);

    
This method will be called by Pig if the job which contains this store fails. Implementations can clean up output locations in this method to ensure that no incorrect/incomplete results are left in the output location

Parameters:
location Location returned by relToAbsPathForStoreLocation(java.lang.String,org.apache.hadoop.fs.Path)
job The org.apache.hadoop.mapreduce.Job object - this should be used only to obtain cluster properties through org.apache.hadoop.mapreduce.task.JobContextImpl.getConfiguration() and not to set/query any runtime job information.
    void cleanupOnFailure(String locationJob jobthrows IOException;

    
This method will be called by Pig if the job which contains this store is successful, and some cleanup of intermediate resources is required. Implementations can clean up output locations in this method to ensure that no incorrect/incomplete results are left in the output location

Parameters:
location Location returned by relToAbsPathForStoreLocation(java.lang.String,org.apache.hadoop.fs.Path)
job The org.apache.hadoop.mapreduce.Job object - this should be used only to obtain cluster properties through org.apache.hadoop.mapreduce.task.JobContextImpl.getConfiguration() and not to set/query any runtime job information.
    void cleanupOnSuccess(String locationJob jobthrows IOException;
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