Version

    ParallelReader

    ParallelReader 64x64

    Short Description

    Ports

    Metadata

    ParallelReader Attributes

    Details

    Examples

    Best Practices

    Compatibility

    See also

    Short Description

    ParallelReader reads data from flat files using multiple threads.

    Component Data source Input ports Output ports Each to all outputs Different to different outputs Transformation Transf. req. Java CTL Auto-propagated metadata

    ParallelReader

    flat file

    0

    1-2

    Ports

    Port type Number Required Description Metadata

    Output

    0

    For correct data records.

    any

    1

    For incorrect data records.

    specific structure, see table bellow.

    Parsed data records are sent to the first output port.

    The component has an optional output logging port for getting detailed information about incorrect records. To get all incorrect records together with the information about the incorrect value, its location, and the error message to error port, Data Policy has to be controlled and an edge has to be connected to the error port.

    Metadata

    ParallelReader has metadata template on the second output port.

    Table 38. Error Metadata for Parallel Reader
    Field Number Field Content Data Type Description

    0

    record number

    long

    The position of the erroneous record in the dataset (record numbering starts at 1).

    1

    field number

    integer

    The position of the erroneous field in the record (1 stands for the first field, i.e. that of index 0).

    2

    original data

    string

    The erroneous record in raw form (including delimiters).

    3

    error message

    string

    The error message - detailed information about the error.

    4

    reading thread offset

    long

    Indicates the initial file offset of the parsing thread (optional field).

    ParallelReader Attributes

    Attribute Req Description Possible values

    Basic

    File URL

    Data source(s) will be read. See Supported File URL Formats for Readers.

    Charset

    Encoding of records that are read in.

    The default encoding depends on DEFAULT_CHARSET_DECODER in defaultProperties.

    UTF-8 | <other encodings>

    Data policy

    Determines what should be done when an error occurs. For more information, see Data Policy.

    Strict (default) | Controlled | Lenient

    Trim strings

    Specifies whether leading and trailing whitespace should be removed from strings before setting them to data fields, see Trimming Data. If true, the use of the robust parser is forced.

    false (default) | true

    Quoted strings

    Fields containing a special character (comma, newline, or double quote) have to be enclosed in quotes. Only single/double quote is accepted as the quote character. If true, special characters are removed when read by the component (they are not treated as delimiters).

    Example: To read input data "25"|"John", switch Quoted strings to true and set Quote character to ". This will produce two fields: 25|John.

    By default, the value of this attribute is inherited from metadata on output port 0. See also Record Details.

    false | true

    Quote character

    Specifies which kind of quotes will be permitted in Quoted strings. By default, the value of this attribute is inherited from metadata on output port 0. See also Record Details.

    both | " | '

    Advanced

    Skip leading blanks

    Specifies whether to skip a leading whitespace (blanks e.g.) before setting input strings to data fields. If not explicitly set (i.e. having the default value), the value of the Trim strings attribute is used. See Trimming Data. If true, the use of the robust parser is enforced.

    false (default) | true

    Skip trailing blanks

    Specifies whether to skip a trailing whitespace (blanks e.g.) before setting input strings to data fields. If not explicitly set (i.e. having the default value), the value of the Trim strings attribute is used. See Trimming Data. If true, the use of the robust parser is enforced.

    false (default) | true

    Number of skipped records per source

    Skips the first n records/rows from each source file. See Selecting Input Records.

    0 (default) - N

    Max error count

    The maximum number of tolerated error records in input file(s); applicable only if Controlled Data Policy is set.

    0 (default) - N

    Treat multiple delimiters as one

    If a field is delimited by a multiplied delimiter char, it will be interpreted as a single delimiter when setting to true.

    false (default) | true

    Verbose

    By default, a less comprehensive error notification is provided and the performance is slightly higher. However, if switched to true, more detailed information with less performance is provided.

    false (default) | true

    Level of parallelism

    The number of threads used to read input data files. The order of records is not preserved if it is 2 or higher. If the file is too small, this value will be switched to 1 automatically.

    2 (default) | 1-n

    Distributed file segment reading

    In case the component is running in a Cluster environment and a shared file is read, each component’s instance process the appropriate part of the file. The whole file is divided into segments by CloverDX Server and each Cluster worker processes only one proper part of the file. By default, this option is turned off. This attribute is ignored for partitioned files.

    false (default) | true

    Parser

    By default, the most appropriate parser is applied. Besides, the parser for processing data may be set explicitly. If an improper one is set, an exception is thrown and the graph fails. See Data Parsers

    auto (default) | <other>

    Details

    ParallelReader reads delimited flat files (e.g. CSV, tab delimited, etc.), fixed-length, or mixed text files. The component can read a single file as well as a collection of files placed on a local disk or remotely, remote files are accessible via FTP and S3 protocol.

    Reading goes in several parallel threads, which improves the reading speed. Input file is divided into set of chunks and each reading thread parses just records from this part of file.

    The component can use either the fast simplistic parser (SimpleDataParser) or the robust (CharByteDataParser) one. Which parser is used depends on the component settings and data structure.

    Speedup

    If you use ParallelReader instead of FlatFileReader, the speed up is more significant with metadata of many date data fields.

    Quoted strings

    The attribute considerably changes the way your data is parsed. If it is set to true, all field delimiters inside quoted strings will be ignored (after the first Quote character is actually read). Quote characters will be removed from the field.

    Example input:

    1;"lastname;firstname";gender

    Output with Quoted strings == true:

    {1}, {lastname;firstname}, {gender}

    Output with Quoted strings == false:

    {1}, {"lastname}, {firstname";gender}

    Examples

    Reading a file with ParallelReader

    This example shows the basic use of ParallelReader.

    Read file file.txt using ParallelReader.

    Solution

    In ParallelReader, specify File URL and connect an edge to the first output port.

    ParallelReader will read it using two threads.

    Best Practices

    We recommend users to explicitly specify Charset.

    Compatibility

    Version Compatibility Notice

    2.8.1

    ParallelReader is included in 2.8.1 and higher.

    4.4.0-M1

    ParallelReader support reading files from S3.