Common Properties of Writers
Last updated
Last updated
Writers are the final components of a transformation graph. They serve to write data to files located on disk or to send data using some FTP, LDAP or JMS connection, or insert data into database tables. Trash component, which discards all records it receives, is categorized as Writer as it can be set to store records in a debug file.
Each Writer must have at least one input port through which the data flows to this graph component from some of the others.
Writers can either append data to an existing file, sheet or database table, or replace the existing content by new one. For this purpose, Writers writing to files have the Append attribute. This attribute is set to false, by default. That means "do not append data, replace it". Replacing database table is available in some bulkloaders.
You can also write data to one file or one database table by more Writers of the same graph; in such a case you should write data by different Writers in different phases.
Most Writers let you see some part of resulting data. Right-click the Writer and select the View data option. You will be prompted with the same View data dialog as when debugging the edges. For more details, see . This dialog allows you to view the written data. It can only be used after graph has already been run.
Below is a brief overview of links to these options:
Below are examples of the File URL attribute for writing to local and remote files, through proxy, output port and dictionary:
As it has been shown in , some Writers allow you to define a transformation. For information about transformation interfaces that must be implemented in transformations written in Java.
database
1
0-2
x
x
x
x
x
EDIFACT file
1-n
0-1
x
x
x
x
x
flat file
1
0-1
x
x
x
x
x
JSON file
1-n
0-1
x
x
x
x
x
LDAP directory tree
1
0-1
x
x
x
x
x
XLS(X) file
1
0-1
x
x
x
x
x
none
1
0
x
x
x
x
x
flat file
1
0-1
x
x
x
x
x
X12 file
1-n
0-1
x
x
x
x
x
XML file
1-n
0-1
x
x
x
x
x
The URL shown below can also contain placeholders – a dollar sign or hash sign.
Dollar and hash signs serve for different purposes.
Dollar sign should be used when each of multiple output files contains only a specified number of records based on the Records per file attribute.
Hash sign should be used when each of multiple output files only contains records corresponding to the value of specified Partition key.
Note: hash signs in URL examples in this section serve to separate a compressed file (zip, gz) from its contents. These are not placeholders.
To ensure graph portability, forward slashes must be used when defining the path in URLs (even on Microsoft Windows).
Below are examples of possible URLs for Writers:
/path/filename.out
Writes specified file on disk.
/path1/filename1.out;/path2/filename2.out
Writes two specified files on disk.
/path/filename$.out
Writes a number of files on disk. The dollar sign represents one digit. Thus, the output files can have the name range from filename0.out to filename9.out. The dollar sign is used when Records per file is set.
/path/filename$$.out
Writes a number of files on disk. Two dollar signs represent two digits. Thus, the output files can have the name range from filename00.out to filename99.out. The dollar sign is used when Records per file is set.
/path/filename#.out
Writes a number of files on disk. If Partition file tag is set to Key file tag, the hash sign in the file name is replaced with Partition key field value. Otherwise, the hash sign is replaced with number.
zip:(/path/file$.zip)
Writes a number of compressed files on disk. The dollar sign represents one digit. Thus, the compressed output files can have the names from file0.zip to file9.zip. The dollar sign is used when Records per file is set.
zip:(/path/file$.zip)#innerfolder/filename.out
Writes a specified file inside the compressed files on disk. The dollar sign represents one digit. Thus, the compressed output files containing the specified filename.out file can have the name range from file0.zip to file9.zip. The dollar sign is used when Records per file is set.
gzip:(/path/file$.gz)
Writes a number of compressed files on disk. The dollar sign represents one digit. Thus, the compressed output files can have the name ranges from file0.gz to file9.gz. The dollar sign is used when Records per file is set.
ftp://user:password@server/path/filename.out
Writes a specified filename.out file on a remote server connected via an FTP protocol using username and password.
sftp://user:password@server/path/filename.out
Writes a specified filename.out file on a remote server connected via an SFTP protocol using a username and password.
If a certificate-based authentication is used, certificates are placed in the ${PROJECT}/ssh-keys/ directory. For more information, see SFTP Certificate in Data Shaper.
Note, that only certificates without a password are currently supported. The certificate-based authentication has a URL without a password:
sftp://username@server/path/filename.txt
zip:(ftp://username:password@server/path/file.zip)#innerfolder/filename.txt
Writes a specified filename.txt file compressed in the file.zip file on a remote server connected via an FTP protocol using username and password.
zip:(ftp://username:password@server/path/file.zip)#innerfolder/filename.txt
Writes a specified filename.txt file compressed in the file.zip file on a remote server connected via an FTP protocol.
zip:(zip:(ftp://username:password@server/path/name.zip)#innerfolder/file.zip)#innermostfolder/filename.txt
Writes a specified filename.txt file compressed in a file.zip file that is also compressed in a name.zip file on a remote server connected via an FTP protocol using username and password.
gzip:(ftp://username:password@server/path/file.gz)
Writes the first file compressed in a file.gz file on a remote server connected via an FTP protocol.
smb2://domain%3Buser:password@server/path/filename.txt
Writes a file to a Windows share (Microsoft SMB version 2 and 3).
The SMB version 2 and 3 protocol is implemented in the SMBJ library.
port:$0.FieldName:discrete
If this URL is used, the output port of the Writer must be connected to another component. Output metadata must contain a FieldName of one of the following data types: string, byte or cbyte. Each data record that is received by the Writer through the input port is processed according to the input metadata, sent out through the optional output port, and written as the value of the specified field of the metadata of the output edge. Next records are parsed in the same way as described here.
http:(direct:)//seznam.cz
Without proxy.
ftp:(proxy://user:password@proxyserver:1234)//seznam.cz
Proxy setting for ftp protocol.
ftp:(proxy://proxyserver:443)//server/path/file.dat
Proxy setting for FTP protocol.
sftp:(proxy://66.11.122.193:443)//user:password@server/path/file.dat
Proxy setting for SFTP protocol.
dict:keyName:source
Writes data to a file URL specified in dictionary. Target file URL is retrieved from the specified dictionary entry.
dict:keyName:discrete [1]
Writes data to dictionary. Creates ArrayList<byte[]>
dict:keyName:stream [2]
Writes data to dictionary. Creates WritableByteChannel
A sandbox resource, whether it is a shared, local or partitioned sandbox, is specified in the graph under the fileURL attributes as a so called sandbox URL like:
sandbox://data/path/to/file/file.dat
where data is a code for sandbox and path/to/file/file.dat is the path to the resource from the sandbox root. The URL is evaluated by Data Shaper Server during graph execution and a component (Reader or Writer) obtains the opened stream from the Server. This may be a stream to a local file or to some other remote resource. Thus, a graph does not have to run on the node which has local access to the resource. There may be more sandbox resources used in the graph and each of them may be on a different node. In such cases, Data Shaper Server would choose the node with the most local resources to minimize remote streams.
The sandbox URL has a specific use for parallel data processing. When the sandbox URL with the resource in a partitioned sandbox is used, that part of graph/phase runs in parallel, according to the node allocation specified by the list of partitioned sandbox locations. Thus, each worker has its own local sandbox resource. Data Shaper Server evaluates the sandbox URL on each worker and provides an open stream to a local resource to the component.
[1] The discrete processing type uses a byte array for storing data.
[2] The stream processing type uses an output stream that must be created before running a graph (from Java code).
After an output file has been created, you can view its data on Writers using the context menu. Simply right-click the desired component, and select Inspect data from the context menu.
Some Writers allow you to write data to the optional output port.
Below is the list of Writers allowing output port writing:
Set the File URL attribute of the Writer to port:$0.FieldName[:processingType].
Here, processingType is optional and can be set to one of the following: discrete or stream. If it is not set explicitly, it is discrete by default.
discrete
The file content is stored into a field (of one record). The data should be small enough to fit into this one field.
If the data is partitioned into multiple files, multiple output records are sent out. Each output record contains input data of one partition.
stream
The file content is written to a stream, which is split into chunks. The chunks are written into a user-specified output field. One chunk goes to one output record, therefore your data does not have to fit into a single data field.
The stream is terminated with another record with null in the field (as a sentinel). If the data is partitioned into multiple files, null also serves as a delimiter between the files.
The count of output records depends on the value of the PortReadingWriting.DATA_LENGTH parameter. The default value is 2,048 B.
If you connect the optional output port of any Writer with an edge to another component, metadata of the edge must contain the specified FieldName of a string, byte or <code<cbyte data type.
When a graph runs, data is read through the input according to the input metadata, processed by the Writer according to the specified processing type and sent subsequently to the other component through the optional output port of the Writer.
If the target file exists, there are two options:
the existing file can be replaced;
the records can be appended to the existing content.
Appending or replacing is configured with the Append attribute.
If Append is set to true, records are appended to the file.
If Append is set to false, the file is overwritten. The default value is false.
You can also append data to files in local (non-remote) zip archives. In server environment, this means [use_local_context_url] has to be set to true.
Append is available in the following Writers:
If you specify a non-existing directory in the File URL, set the Create directories attribute to true. The directory will be created. Otherwise, the graph would fail.
The default value of Create directories is false.
The Create directories attribute is available in the following Writers:
The limit on the number of written records is set up with Max number of records.
The number of records to be skipped is set up with Number of skipped records.
The following components let you set up Max number of records or Number of skipped records:
Some Writers let you part the incoming data flow and distribute the records among different output files. The components are:
You can part data according to the number of records or classified according to values of specified fields.
Partitioning by number of records saves at most N records into one file. The other records are saved into another file until the limit is reached and so forth. Use Records per file attribute to set up the limit N.
Example: part 450 record into output files. Each output file has at most 100 record.
Solution: File URL value should contain $ sign(s). The $ signs will be replaced with digits.
File URL
${DATAOUT_DIR}/output_$$.txt
Records per file
100
Records can be parted into multiple output files according to a data field value. The field is specified with the Partition key attribute.
The placeholder # in output file name can be replaced with a field value or with integer. If Partition file tag is set to Number file tag, the placeholder is replaced with integer. If Partition file tag is set to Key file tag, the placeholder is replaced with a field value. The default value is Number file tag.
The partition key consists of a list of fields forming the partition key. The list has the form of a sequence of incoming record field names separated by a semicolon.
Example: part data according to the field1 field. Use the field value as a part of output file name.
File URL
${DATAOUT_DIR}/output_#.txt
Partition key
field1
Partition file tag
Key file tag
If you use two or more fields for partitioning, use the placeholder # on one place in the file URL: ${DATAOUT_DIR}/output_#.txt. Do not use the placeholder for each key field.
Partitioning using a lookup table lets you part records using input field values. The values of Partition key serve as a key to be looked up in the lookup table. A value corresponding to the key defines a group.
A group can form its name with a number or value from a lookup table.
Each group is written to its own output file.
The difference between partitioning according to a data field value, and partitioning using a lookup table is that in the first case, one unique Partition key value creates one group, whereas in the latter one, a single group can correspond to multiple different Partition key values.
Example: input data contain the field city as well as other fields. The lookup table contains city and country. Part data into files: each file should contain records corresponding to one country. Records with unmatched cities should have unmatched instead of the country.
File URL
${DATAOUT_DIR}/output_#.txt
Partition key
field1
Partition lookup table
TheLookupTable
Partition file tag
Key file tag
Partition output fields
country
Partition unassigned file name
unmatched
Remember that if all incoming records are assigned to the values of lookup table, the file for unassigned records will be empty (even if it is defined).
You can use partitioning using a lookup table to write a subset of input records. For example, you can only write records corresponding to some countries (from previous example). To constrain the records, define values of desired fields in lookup table (key fields) and leave Partition unassigned file name blank.
You can combine partitioning by number of records and partitioning according to data field value.
Example: part data according to the field1 field. Use the field value as a part of output file name. Write at most 100 records into one file.
File URL
${DATAOUT_DIR}/output_#_$.txt
Records per file
100
Partition key
field1
Partition file tag
Key file tag
The # sign is replaced with a field1 value. The $ sign is replaced with integer according to number of record with same field1 value.
The partitioning algorithm keeps all output files open at once. This could lead to an undesirable memory footprint for many output files (thousands). Moreover, for example unix-based OS usually have very strict limitation of number of simultaneously open files (1,024) per process.
In case you run into one of these limitations, consider sorting the data according to the partition key using one of our standard sorting components and set the Sorted input attribute to true. The partitioning algorithm does not need to keep open all output files, just the last one is open at one time.
The File URL value only serves as a base name for the output file names. The base name should contain placeholders - dollar sign or hash sign.
The dollar sign is replaced with a number. If you use more dollar signs, each $ is replaced with one digit. This way, leading zeros can be inserted. Use $ if you part according to number of records.
The hash sign is replaced with a number, field value, or value from a lookup table. Leading zeros can be created with more hash signs. Use # if you part according to field value or using lookup table.
You should differentiate between hash sign and dollar sign usage.
Hash sign A hash sign should be used when each of multiple output files only contains records corresponding to the value of specified Partition key.
Dollar sign A dollar sign should be used when each of multiple output files contains only a specified number of records based on the Records per file attribute.
The hash(es) can be inserted in any place of this file part of File URL, even in the middle. For example: path/output#.xls (in the case of the output XLS file).
If Partition file tag is set to Number file tag, output files are numbered and the count of hashes used in File URL means the count of digits for these distinguishing numbers. This is the default value of Partition file tag. Thus, ### can go from 000 to 999.
If Partition file tag is set to Key file tag, a single hash must be used in File URL at most. Distinguishing names are used.
These distinguishing names will be created as follows:
If the Partition key attribute (or the Partition output fields attribute) is of the following form: field1;field2;…​;fieldN and the values of these fields are the following: valueofthefield1, valueofthefield2, …​, valueofthefieldN, all the values of the fields are converted to strings and concatenated. The resulting strings will have the following form: valueofthefield1valueofthefield2…​valueofthefieldN. Such resulting strings are used as distinguishing names and each of them is inserted to the File URL into the place marked with hash, or appended to the end of File URL if no hash is used in File URL.
For example, if firstname;lastname is the Partition key (or Partition output fields), you can have the output files as follows:
path/outjohnsmith.xls, path/outmarksmith.xls, path/outmichaelgordon.xls, etc. (if File URL is path/out#.xls and Partition file tag is set to Key file tag).
Or path/out01.xls, path/out02.xls. etc. (if File URL is path/out##.xls and Partition file tag is set to Number file tag).
Some components without output mapping let you omit particular fields from results. Use the Exclude fields attribute and specify metadata fields that should not be written to the output. It has a form of a sequence of field names separated by a semicolon. The field names can be typed manually of created using a key dialog.
Excluding fields attribute is available in:
If you part data and Partition file tag is set to Key file tag, values of Partition key form the names of output files, and the values are written to the corresponding files as well. To avoid saving the same information twice, you can select the fields that will be excluded from writing.
Use the Exclude fields attribute to specify fields that should not be written into output files. The fields will only be a part of file or sheet names, but will not be written to the contents of these files.
When you read these files back, you can acquire the values with an autofilling function source_name.
Example: when you have files created using Partition key set to City and the output files are London.txt, Stockholm.txt, etc., you can get these values (London, Stockholm, etc.) from the file names. The City field values do not need to be contained in the files.
The File URL attribute lets you type in the file URL directly, or open the .
Writes a specified filename.out file on a remote server connected via a WebDAV protocol using username and password.
s3://access_key_id:/bucketname/path/filename.out
Writes to path/filename.out object located in the Amazon S3 web storage service in a bucket bucketname using an access key ID and secret access key.
See.
It is recommended to connect to S3 via a _region-specific_ S3 URL: s3://s3.eu-central-1.amazonaws.com/bucket.name/. A region-specific URL have much better performance than a generic one (s3://s3.amazonaws.com/bucket.name/).
See recommendation on the .
az-blob://account:/containername/path/filename.txt
Writes to path/filename.out object located in the Azure Blob Storage service in the specified container.
Connects using the specified Account Key. See for other authentication options.
hdfs://CONN_ID/path/filename.dat
Writes a file on a Hadoop distributed file system (HDFS). To which HDFS NameNode to connect to is defined in a with CONN_ID. This example file URL writes a file with /path/filename.dat absolute HDFS path.
smb://domain%3Buser:password@server/path/filename.txt
Writes a file to a Windows share (Microsoft SMB version 1/CIFS protocol). The server part may be a DNS name, an IP address or a NetBIOS name. The Userinfo part of the URL (domain%3Buser:password) is not mandatory and any URL reserved character it contains should be escaped using the %-encoding similarly to the semicolon ; character with %3B in the example (the semicolon is escaped because it collides with the default Data Shaper file URL separator). Also note that the dollar sign $ in the URL path (e.g. in the case of writing to an Administrative share) is reserved for the file partitioning feature so it too needs be escaped (with %24).
The SMB protocol is implemented in the JCIFS library which may be configured using Java system properties. For a list of all configurable properties, see in JCIFS documentation.
http:(proxy://user::443)//seznam.cz
Proxy setting for HTTP protocol.
s3:(proxy://user::443)//access_key_id:/bucketname/path/filename.out
Proxy setting for S3 protocol.
See also
See .
The same can be done in some of the Readers. See .
The attributes for the output port writing in these components may be defined using the .
(the Debug append attribute)
Writers let you limit the records that should be written. You can limit the number of records to be written and skip the specified number of records. If you need to apply a filter on output records, use before the Writer.
(Number of skipped records only)