CloverDataReader
Not available in Community Designer
Short Description
CloverDataReader reads data stored in our internal binary Clover data format files. It can also read data from compressed files, or dictionary.
| Component | Data source | Input ports | Output ports | Each to all outputs | Different to different outputs | Transformation | Transf. req. | Java | CTL | Auto-propagated metadata |
|---|---|---|---|---|---|---|---|---|---|---|
| CloverDataReader | clover binary file | 1 | 1-n |  |  | | | | | |
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Ports
| Port type | Number | Required | Description | Metadata |
|---|---|---|---|---|
| Input | 0 |
| For Input Port Reading correct data records | Include specific byte/cbyte field |
| Output | 0 |
| For correct data records | Any |
| 1-n | | For correct data records | Output 0 |
Metadata
CloverDataReader does not propagate metadata.
CloverDataReader has no metadata template, but it can extract metadata from clover file and propagate it forward as it would have a template. (Available since 4.1.0-M1)
Metadata on the input port has to include a byte or cbyte or string field.
Metadata on output port has to be the same as metadata of data from the file.
Metadata can use Autofilling Functions.
CloverDataReader Attributes
| Attribute | Req | Description | Possible values |
|---|---|---|---|
| Basic | |||
| File URL | yes | Attribute specifying what data source(s) will be read (Clover data file, input port, dictionary). See Supported File URL Formats for Readers. | |
| Advanced | |||
| Number of skipped records | Number of records to be skipped. See Selecting Input Records. | 0-N | |
| Max number of records | Maximum number of records to be read. See Selecting Input Records. | 0-N | |
| Number of skipped records per source | Skip the first n records of each file. | 0-N | |
| Max number of records per source | Reads maximally n records from each file. | 0-N | |
| Deprecated | |||
| Index file URL | Name of the index file, including path. If not specified, all records are read. | ||
| Start record | Has exclusive meaning: Last record before the first that is already read. Has lower priority than Number of skipped records. | 0 (default) | 1-n | |
| Final record | Has inclusive meaning: Last record to be read. Has lower priority than Max number of records. | all (default) | 1-n | |
Examples
| Reading a Clover Data File |
| Omitting Leading Records |
| Omitting Leading Records of Each File |
| Reading at most n Records in Total |
| Reading at most n Records per File |
Reading a Clover Data File
Read all records from the Clover data file.
Solution
Set up the File URL attribute.
| Attribute | Value |
|---|---|
| File URL | ${DATAIN_DIR}/my-clover-file.cdf |
CloverDataReader will read all the records from the file(s).
Omitting Leading Records
You have two Clover data files. First 3 records contain uninteresting data and should not be read. The uninteresting records are in the first file. (The records have been sorted and partitioned for example.)
greengrocers1.cdf
bread honey raisins pears plums
greengrocers2.cdf
carrot peas radish
Solution
Set up File URL and Number of skipped records attributes.
| Attribute | Value |
|---|---|
| File URL | ${DATAIN_DIR}/greengrocers1.cdf;${DATAIN_DIR}/greengrocers2.cdf |
| Number of skipped records | 3 |
CloverDataReader reads the following items:
pears plums carrot peas radish
Omitting Leading Records of Each File
There are two Clover data files: list1.cdf and list2.cdf.
Each file starts with one record to be omitted.
list1.cdf
Goods cardigan shirt trousers
list2.cdf
Goods shoes sox
Solution
Set up File URL and Number of skipped records per source attributes.
| Attribute | Value |
|---|---|
| File URL | ${DATAIN_DIR}/list1.cdf;${DATAIN_DIR}/list2.cdf |
| Number of skipped records per source | 1 |
CloverDataReader sends the following records to the output:
cardigan shirt trousers shoes sox
Reading at most n Records in Total
You have three files stationery1.cdf, stationery2.cdf and stationery3.cdf
and you need to read six records in total from all files.
stationery1.cdf
pen pencil marker paintbrush
stationery2.cdf
ink water colors oil colors
stationery3.cdf
notebook coloring book
Solution
Set up File URL and Max number of records attributes.
| Attribute | Value |
|---|---|
| File URL | ${DATAIN_DIR}/stationery1.cdf;${DATAIN_DIR}/stationery2.cdf;${DATAIN_DIR}/stationery3.cdf |
| Max number of records | 6 |
CloverDataReader sends all 4 records from stationery1.cdf and 2 of 3 records from stationery2.cdf to the output port.
No record from the file stationery3.cdf is sent the output port as the limit has been reached already.
pen pencil marker paintbrush ink water colors
Reading at most n Records per File
You have three Clover data files (stationery[1-3].cdf) from the previous example.
Read at most 3 records from each file.
Solution
Set up File URL and Max number of records per source attributes.
| Attribute | Value |
|---|---|
| File URL | ${DATAIN_DIR}/stationery1.cdf;${DATAIN_DIR}/stationery2.cdf;${DATAIN_DIR}/stationery3.cdf |
| Max number of records per source | 3 |
CloverDataReader reads 3 records from stationery1.cdf,
3 records from stationery2.cdf and 2 of 2 records from stationery3.cdf.
pen pencil marker ink water colors oil colors notebook coloring book
Compatibility
2.9
Since 2.9 version of CloverETL, CloverDataWriter also writes a header to output files with the version number. For this reason, CloverDataReader expects that files in Clover binary format contain such a header with the version number. CloverDataReader 2.9 cannot read files written by older versions of CloverETL nor these older versions can read data written by CloverDataWriter 2.9.
4.0
The internal structure of the zip archive has changed.
Graphs that rely on the structure will stop working.
Graphs that use plain zip file URL without internal entry specification are not affected:
CloverDataReader with File URL zip:(${DATAOUT_DIR}/employees.zip)#DATA/employees
will need to be fixed to use zip:(${DATAOUT_DIR}/employees.zip) instead.
4.1.0-M1
Since 4.1.0-M1, CloverDataReader can extract metadata template from clover file. It can be seen as a metadata template corresponding to the file.
4.4.0-M2
Since 4.4.0-M2, CloverDataReader can read from input port just from byte or cbyte field.