hbScanParameter (Type of variable)

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Properties specific to the description of hbScanParameter variables
Iterating over data with the filter
Examples of filters

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hbScanParameter (Type of variable)

In french: hbParamètreScan

The hbScanParameter type is used to define the parameters for iterating over the records in an HBase database. The characteristics of these iteration parameters can be defined and modified using different WLanguage properties.

Remark: For more details on the declaration of this type of variable and the use of WLanguage properties, see Declaring a variable.

Example

// Connection
Connection is hbConnection
Connection.Server = "MyServer"
// Filter description
MyScan is hbScanParameter
MyScan.Connection = Connection
MyScan.Table = "blog"
// Filters, for all the rows, the values of columns whose name starts with "Title"
MyScan.Filter = "{ ""type"": ""ColumnPrefixFilter"", ""value"": """ + ...
Encode("Title", encodeBASE64) + """ }"
// Loops through and displays the filtered data
// MyResult is an hbScanResult variable
FOR EACH MyResult OF MyScan
Trace("The column " + MyResult.Column.Family + ":" + ...
MyResult.Column.Qualifier + ...
" of the row " + MyResult.Row + " is set to " + MyResult.Value)
END

Remarks

Properties specific to the description of hbScanParameter variables

The following properties can be used to handle the description of iteration parameters:

Property name	Type used	Effect

Column	Array of hbColumn	Families or columns (items) found in the result of the iteration.
Connection	hbConnection variable	Connection to the HBase server to be used for the iteration.
StartTimestamp	DateTime	Start date and time for selecting rows. The iteration will only return the rows containing cells from this date and time.
EndTimestamp	DateTime	End date and time for selecting rows. The iteration will only return the rows containing cells up to this date and time.
Filter	Character string	Filter that will be applied during the iteration. This filter is in JSON format. The literal values must be encoded in Base64, by using Encode for example. See the HBase documentation for more details.
StartRow	Buffer	Identifier of the first row (record) of the iteration. This row will be included in the iteration.
EndRow	Buffer	Identifier of the last row (record) of the iteration. This row will not be included in the iteration.
MaxVersion	Integer	Maximum number of versions returned for each cell (value of item). Indeed, a history of values is stored in the HBase database for each cell.
Table	Character string	Name of the HBase table to iterate over.

Iterating over data with the filter

To iterate over data with a filter:

Define the Filter property of the variable.
Use the FOR EACH syntax to initialize the iteration with the filter. The following syntax must be used:

FOR EACH <Result> ON <Variable Of Scan Setting>

In this syntax, <Result> is a hbScanResult (see the example).

Examples of filters

Filter on the column value: MyFamily:MyQualifier = ‘Value'

MyScan.Filter = ...
"{" + ...
"""type"": ""SingleColumnValueFilter""," + ...
"""op"": ""EQUAL""," + ...
"""family"": """ + Encode("MyFamily", encodeBASE64) + """," + ...
"""qualifier"": """ + Encode("MyQualifier", encodeBASE64) + """," + ...
"""latestVersion"": true," + ...
"""comparator"": {" + ...
"""type"": ""BinaryComparator""," + ...
"""value"": """ + Encode("Value", encodeBASE64) + """}" + ...
"}"
Filter the columns whose name starts with "Title":

MyScan.Filter = ...
"{" + ...
"""type"": ""ColumnPrefixFilter""," + ...
"""value"": """ + Encode("Title", encodeBASE64) + """," + ...
"}"
Filter the data according to several filters:

MyScan.Filter = ...
"{" + ...
"""type"": ""FilterList""," + ...
"""op"": ""MUST_PASS_ALL""," + ...
"""filters"": [" + ...
"{" + ...
filter1 + ...
"}," + ...
"{" + ...
filter2 + ...
"}" + ...
"]" + ...
"}"