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Package com.gpudb

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Class RecordRetriever<T>

java.lang.Object
com.gpudb.RecordRetriever<T>
Type Parameters:
T - the type of object being retrieved
public class RecordRetriever<T> extends Object
Object that permits efficient retrieval of records from GPUdb, with support for multi-head access. RecordRetriever instances are thread safe and may be used from any number of threads simultaneously.

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    Constructor Details

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    Method Details

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      getGPUdb

      public GPUdb getGPUdb()
      Gets the GPUdb instance from which records will be retrieved.
      Returns:
      the GPUdb instance from which records will be retrieved

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      getTableName

      public String getTableName()
      Gets the name of the table from which records will be retrieved.
      Returns:
      the name of the table from which records will be retrieved

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      isUsingHeadRank

      public boolean isUsingHeadRank()
      Returns:
      whether this RecordRetriever object is using the head-rank to do a simple record fetching (not utilizing the server’s key lookup feature) (true value), or using multi-head (the worker ranks) for key lookup (false value).

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      isDoingWorkerLookup

      public boolean isDoingWorkerLookup()
      Returns:
      whether this RecordRetriever object is using the worker ranks to do key lookups (true value), or doing simple record fetching (not the server’s key lookup feature) (false value). Note that this will not reflect the non-worker lookup scenario where only an expression is supplied and the table is sharded.

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      getOptions

      public Map<String,String> getOptions()
      Gets the options currently used for the retriever methods. Note that any GetRecordsRequest.Options.EXPRESSION options will get overridden at the next getByKey(java.util.List<java.lang.Object>, java.lang.String) call with the appropriate expression.
      Returns:
      the options used during record retrieval
      See Also:

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      setOptions

      public RecordRetriever<T> setOptions(Map<String,String> options)
      Sets the options to be used for the retriever methods.
      Parameters:
      options - the options to be used during record retrieval
      Returns:
      the current RecordRetriever instance
      See Also:

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      getByKey

      public GetRecordsResponse<T> getByKey(List<Object> keyValues, String expression) throws GPUdbException
      Retrieves records with the given key values and filter expression from the database using a direct-to-rank fast key lookup, if possible, and falling back to a standard lookup via the head node, if not.
      This method operates in four modes, depending on the parameters passed:
      • keyValues only - attempts a direct-to-rank lookup for records matching the given key values
      • keyValues and expression - attempts a direct-to-rank lookup for records matching the given key values, filtering them by the given expression
      • expression only - requests, via the head rank, all records in the table matching the given filter expression
      • neither - retrieves all records from the table via the head rank
      Parameters:
      keyValues - the key values to use for the lookup; these must correspond to either the explicit or implicit shard key for sharded tables or the primary key of replicated tables
      expression - a filter expression that will be applied to the data requested by the key values; if no key values are specified this filter will be applied to all of the data in the target table
      Returns:
      a GetRecordsResponse with the requested records
      Throws:
      GPUdbException

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      getByKey

      public GetRecordsResponse<T> getByKey(List<Object> keyValues, String expression, long offset) throws GPUdbException
      Retrieves records with the given key values and filter expression from the database using a direct-to-rank fast key lookup, if possible, and falling back to a standard lookup via the head node, if not. Returns records in the overall result set starting from the given offset.
      This method operates in four modes, depending on the parameters passed:
      • keyValues only - attempts a direct-to-rank lookup for records matching the given key values
      • keyValues and expression - attempts a direct-to-rank lookup for records matching the given key values, filtering them by the given expression
      • expression only - requests, via the head rank, all records in the table matching the given filter expression
      • neither - retrieves all records from the table via the head rank
      Parameters:
      keyValues - the key values to use for the lookup; these must correspond to either the explicit or implicit shard key for sharded tables or the primary key of replicated tables
      expression - a filter expression that will be applied to the data requested by the key values; if no key values are specified this filter will be applied to all of the data in the target table
      offset - offset of the record(s) within the result set to return
      Returns:
      a GetRecordsResponse with the requested records
      Throws:
      GPUdbException

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      getColumnsByKey

      public GetRecordsByColumnResponse getColumnsByKey(List<String> columns, List<Object> keyValues, String expression) throws GPUdbException
      Retrieves records with the given key values and filter expression from the database using a direct-to-rank fast key lookup, if possible, and falling back to a standard lookup via the head node, if not.
      This method operates in four modes, depending on the parameters passed:
      • keyValues only - attempts a direct-to-rank lookup for records matching the given key values
      • keyValues and expression - attempts a direct-to-rank lookup for records matching the given key values, filtering them by the given expression
      • expression only - requests, via the head rank, all records in the table matching the given filter expression
      • neither - retrieves all records from the table via the head rank
      Parameters:
      columns - The requested columns (which can include expressions) being requested. May use ”*” for all columns.
      keyValues - the key values to use for the lookup; these must correspond to either the explicit or implicit shard key for sharded tables or the primary key of replicated tables
      expression - a filter expression that will be applied to the data requested by the key values; if no key values are specified this filter will be applied to all of the data in the target table
      Returns:
      a GetRecordsResponse with the requested records
      Throws:
      GPUdbException

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      getColumnsByKey

      public GetRecordsByColumnResponse getColumnsByKey(List<String> columns, List<Object> keyValues, String expression, long offset) throws GPUdbException
      Retrieves records with the given key values and filter expression from the database using a direct-to-rank fast key lookup, if possible, and falling back to a standard lookup via the head node, if not. Returns records in the overall result set starting from the given offset.
      This method operates in four modes, depending on the parameters passed:
      • keyValues only - attempts a direct-to-rank lookup for records matching the given key values
      • keyValues and expression - attempts a direct-to-rank lookup for records matching the given key values, filtering them by the given expression
      • expression only - requests, via the head rank, all records in the table matching the given filter expression
      • neither - retrieves all records from the table via the head rank
      Parameters:
      columns - The requested columns (which can include expressions) being requested. May use ”*” for all columns.
      keyValues - the key values to use for the lookup; these must correspond to either the explicit or implicit shard key for sharded tables or the primary key of replicated tables
      expression - a filter expression that will be applied to the data requested by the key values; if no key values are specified this filter will be applied to all of the data in the target table
      offset - offset of the record(s) within the result set to return
      Returns:
      a GetRecordsResponse with the requested records
      Throws:
      GPUdbException