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- Properties specific to the description of hbScanParameter variables
- Iterating over data with the filter
- Examples of filters
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 changed 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.
// 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. | | EndRow | Buffer | Identifier of the last row (record) of the iteration. This row will not be included in the iteration. | | 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. | | 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. | | StartRow | Buffer | Identifier of the first row (record) of the iteration. This row will be included in 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. | | 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 + ...
"}" + ...
"]" + ...
"}"
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