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RxTeradata: Generate Teradata Data Source Object

  • Artículo

Description

This is the main generator for S4 class RxTeradata, which extends RxDataSource.

Usage

  RxTeradata(table = NULL, sqlQuery = NULL, dbmsName = NULL, databaseName = NULL, 
             connectionString = NULL, user = NULL,  password = NULL, teradataId = NULL,
             rowBuffering = TRUE, trimSpace = NULL, returnDataFrame = TRUE, stringsAsFactors = FALSE, 
             colClasses = NULL, colInfo = NULL, rowsPerRead = 500000, verbose = 0,
             tableOpClause = NULL, writeFactorsAsIndexes = FALSE,
               ...  ) 

 ## S3 method for class `RxTeradata':
head  (x, n = 6L, reportProgress = 0L,   ...  )
 ## S3 method for class `RxTeradata':
tail  (x, n = 6L, addrownums = TRUE, reportProgress = 0L,   ...  )

Arguments

table

NULL or character string specifying the table name. Cannot be used with sqlQuery.

sqlQuery

NULL or character string specifying a valid SQL select query. Cannot contain hidden characters such as tabs or newlines. Cannot be used with table.

dbmsName

NULL or character string specifying the Database Management System (DBMS) name.

databaseName

NULL or character string specifying the name of the database.

connectionString

NULL or character string specifying the connection string.

user

NULL or character string specifying the user name.

password

NULL or character string specifying the password.

teradataId

NULL or character string specifying the teradataId.

rowBuffering

logical specifying whether or not to buffer rows on read from the database. If you are having problems with your ODBC driver, try setting this to FALSE.

trimSpace

logical specifying whether or not to trim the white character of string data for reading.

returnDataFrame

logical indicating whether or not to convert the result from a list to a data frame (for use in rxReadNext only). If FALSE, a list is returned.

stringsAsFactors

logical indicating whether or not to automatically convert strings to factors on import. This can be overridden by specifying "character" in colClasses and colInfo. If TRUE, the factor levels will be coded in the order encountered. Since this factor level ordering is row dependent, the preferred method for handling factor columns is to use colInfo with specified "levels".

colClasses

character vector specifying the column types to use when converting the data. The element names for the vector are used to identify which column should be converted to which type.

  • Allowable column types are:

    • "logical" (stored as uchar),
    • "integer" (stored as int32),
    • "float32" (the default for floating point data for .xdf files),
    • "numeric" (stored as float64 as in R),
    • "character" (stored as string),
    • "factor" (stored as uint32),
    • "int16" (alternative to integer for smaller storage space),
    • "uint16" (alternative to unsigned integer for smaller storage space),
    • "Date" (stored as Date, i.e. float64)

  • Note for "factor" type, the levels will be coded in the order encountered. Since this factor level ordering is row dependent, the preferred method for handling factor columns is to use colInfo with specified "levels".

  • Note that equivalent types share the same bullet in the list above; for some types we allow both 'R-friendly' type names, as well as our own, more specific type names for .xdf data.

  • Note also that specifying the column as a "factor" type is currently equivalent to "string" - for the moment, if you wish to import a column as factor data you must use the colInfo argument, documented below.

colInfo

list of named variable information lists. Each variable information list contains one or more of the named elements given below. The information supplied for colInfo overrides that supplied for colClasses.

  • Currently available properties for a column information list are:
  • type - character string specifying the data type for the column. See colClasses argument description for the available types.
  • newName - character string specifying a new name for the variable.
  • description - character string specifying a description for the variable.
  • levels - character vector containing the levels when type = "factor". If the levels property is not provided, factor levels will be determined by the values in the source column. If levels are provided, any value that does not match a provided level will be converted to a missing value.
  • newLevels - new or replacement levels specified for a column of type "factor". It must be used in conjunction with the levels argument. After reading in the original data, the labels for each level will be replaced with the newLevels.
  • low - the minimum data value in the variable (used in computations using the F() function.
  • high - the maximum data value in the variable (used in computations using the F() function.

rowsPerRead

number of rows to read at a time.

verbose

integer value. If 0, no additional output is printed. If 1, information on the odbc data source type (odbc or odbcFast) is printed.

writeFactorsAsIndexes

logical. If TRUE, when writing to an RxOdbcData data source, underlying factor indexes will be written instead of the string representations.

...

additional arguments to be passed directly to the underlying functions, including the Teradata Export driver. One important attribute that can be passed is the TD_SPOOLMODE attribute, which RevoScaleR sets to "NoSpool" for efficiency. If you encounter difficulties while extracting data, you might want to specify TD_SPOOLMODE="Spool". To tune performance, use the TD_MIN_SESSIONS and TD_MAX_SESSIONS arguments to specify the minimum and maximum number of sessions. If these are not specified, the default values of 1 and 4, respectively, are used. TD_TRACE_LEVEL specifies the types of diagnostic messages written by each instance of the driver to an external log file. Setting it to 1 turns off tracing (the default), 2 activates the tracing function for driver specific activities, 3 activates the tracing function for interaction with the Teradata Database, 4 activates the tracing function for activities related to the Notify feature, 5 activates the tracing function for activities involving the opcommon library, and 7 activates tracing for all of the above activities. TD_TRACE_OUTPUT specifies the name of the external file used for tracing messages. If a file with the specified name already exists, that file will be overwritten. TD_OUTLIMIT limits the number of rows that the Export driver exports. TD_MAX_DECIMAL_DIGITS specifies the maximum number of decimal digits (a value for the maximum precision) to be returned by the database. The default value is 18, and values above that are not supported. See Chapter 6 of the Teradata Parallel Transporter Application Programming Interface Programmer Guide for details on allowable attributes.

x

an RxTeradata object

n

positive integer. Number of rows of the data set to extract.

addrownums

logical. If TRUE, row numbers will be created to match the original data set.

reportProgress

integer value with options:

  • 0: no progress is reported.
  • 1: the number of processed rows is printed and updated.
  • 2: rows processed and timings are reported.
  • 3: rows processed and all timings are reported.

tableOpClause

Deprecated.

Details

The tail method is not functional for this data source type and will report an error.

The RxTeradata data source behaves differently depending upon the compute context currently in effect. In a local compute context, RxTeradata uses the Teradata Parallel Transporter's Export driver to read large quantities of data quickly from Teradata.

To use the Teradata connector, you need Teradata ODBC drivers and the Teradata Parallel Transporter installed on your client using the Teradata 14.10 or 15.00 client installer, and you need a high-speed connection (100 Mbps or above) to a Teradata appliance running version 14.0 or later.

The user, password, and teradataId arguments take precedence over equivalent information provided within the connectionString argument. If, for example, you provide the user name in both the connectionString and user arguments, the one in connectionString is ignored.

Value

object of class RxTeradata.

Author(s)

Microsoft Corporation Microsoft Technical Support

References

Teradata Corporation (2012). SQL Fundamentals.

Teradata Corporation (2012). Teradata Parallel Transporter Application Programming Interface Programmer Guide

See Also

RxTeradata-class, rxNewDataSource, rxImport.

Examples


 ## Not run:

# Create a Teradata data source
# Note: for improved security, read connection string from a file, such as
# teradataConnString <- readLines("tdConnString.txt")

teradataConnString <- "DRIVER=Teradata;DBCNAME=hostname;DATABASE=RevoTestDB;UID=DBUser;PWD=Password;"

rxTeradataDS <- RxTeradata(sqlQuery = "SELECT * FROM RevoTestDB.claims",
                              connectionString = teradataConnString)

# Create an xdf file name
claimsXdfFileName <- file.path(tempdir(), "importedClaims.xdf")

# Import the data into the xdf file
rxImport(rxTeradataDS, claimsXdfFileName, overwrite = TRUE)

# Read xdf file into a data frame
claimsIn <- rxDataStep(inData = claimsXdfFileName)
head(claimsIn)
## End(Not run)