hbScanParameter (Type of variable)

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Properties specific to the description of hbScanParameter variables
Browsing data according to 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 of a browse performed in a HBase table. The characteristics of these browse parameters can be defined and modified by several WLanguage properties.

Remark: See Declaring a variable for more details on the declaration of this type of variable and the use of WLanguage properties.

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"": """ + ...
Crypt("Title", "", compressNone + cryptNone, encodeBASE64) + """ }"
// Browse the filter and display the filtered data
// The type of the browse variable MyResult is hbScanResult
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 browse parameters:

Property name	Type used	Effect

Column	Array of hbColumn	Families or columns (items) found in the browse result.
Connection	hbConnection variable	Connection to the HBase server that will be used for the browse.
StartTimestamp	DateTime	Start date and time for selecting rows. The browse will return the rows containing cells from this date and time.
EndTimestamp	DateTime	End date and time for selecting rows. The browse will return the rows containing cells up to this date and time.
Filter	Character string	Filter that will be applied during the browse. This filter is in JSON format. The literal values must be encoded in Base64, by using Encrypt for example. See the HBase documentation for more details.
StartRow	Buffer	Identifier of the row (record) for start of browse. This row will be included in the browse.
EndRow	Buffer	Identifier of the row (record) for end of browse. This row will not be included in the browse.
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 HBase table to browse.

Remark: These properties can be handled by using one of the following syntaxes:

<Variable name>..<Property name>
<Variable name>.<Property name>

Browsing data according to the filter

To browse data according to a filter, you must:

Define the ..Filter property of the variable.
Use the FOR EACH syntax to initialize the browse 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"": """ + Crypt("MyFamily", "", compressNone + cryptNone, encodeBASE64) + """," + ...
"""qualifier"": """ + Crypt("MyQualifier", "", ...
compressNone + cryptNone, encodeBASE64) + """," + ...
"""latestVersion"": true," + ...
"""comparator"": {" + ...
"""type"": ""BinaryComparator""," + ...
"""value"": """ + Crypt("Value", "", ...
compressNone + cryptNone, encodeBASE64) + """}" + ...
"}"
Filter the columns whose name starts with "Title":

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

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