Version

    ParallelReader

    Short Description
    Ports
    Metadata
    ParallelReader Attributes
    Details
    Examples
    Best Practices
    Compatibility
    See also

    Short Description

    ParallelReader reads data from flat files using multiple threads.

    ComponentData sourceInput portsOutput portsEach to all outputsDifferent to different outputsTransformationTransf. req.JavaCTLAuto-propagated metadata
    ParallelReaderflat file01-2

    Ports

    Port typeNumberRequiredDescriptionMetadata
    Output0For correct data records.any
    1For 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 55.11. Error Metadata for Parallel Reader

    Field NumberField ContentData TypeDescription
    0record numberlongThe position of the erroneous record in the dataset (record numbering starts at 1).
    1field numberintegerThe position of the erroneous field in the record (1 stands for the first field, i.e. that of index 0).
    2original datastringThe erroneous record in raw form (including delimiters).
    3error messagestringThe error message - detailed information about the error.
    4reading thread offsetlongIndicates the initial file offset of the parsing thread (optional field).

    ParallelReader Attributes

    AttributeReqDescriptionPossible values
    Basic
    File URLData 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

    VersionCompatibility Notice
    2.8.1ParallelReader is included in 2.8.1 and higher.
    4.4.0-M1ParallelReader support reading files from S3.