The Comment text term type allows to filter features based on the the text written in comments on the feature or on the feature's observations.
Setting |
Description |
Use comment on |
Specifies if the filter uses comments features or the comments of observations |
Comparison operator |
The comparison operator used, see Table 2 for details |
Comparison string |
The comparison string can be up to 4000 characters. |
Matching criteria |
•Any: Filter will match if any comment of the feature or the feature's observations (depending on the Comment on setting) matches. •All: Filter will match if all comments of the feature or the feature's observations (depending on the Comment on setting) matches. •None: Filter will match if no comment of the feature or the feature's observations (depending on the Comment on setting) matches. |
Table 1: Settings for this view filter term type
Operator |
Description |
Equal |
Tests for an exact but case insensitive match with the given comparison string. Wildcard characters are not supported, therefore user can search for special characters like %,[], ^, _. |
Contains |
Filters for all strings that contain the given comparison string.Comparison is done case insensitive. Wildcard characters are not supported, therefore user can search for special characters like %,[], ^, _. |
Start with |
Filters for all strings that start with the given comparison string. Comparison is done case insensitive. Wildcard characters are not supported, therefore user can search for special characters like %,[], ^, _. |
Ends with |
Filters for all strings that end with the given comparison string. Comparison is done case insensitive. Wildcard characters are not supported, therefore user can search for special characters like %,[], ^, _. |
Pattern |
Filters for all strings that contain the given comparison pattern. Comparison is done case insensitive. Wildcard characters are supported in the comparison pattern. |
Table 2: Comparison operators
Wildcards in comparison string
Wildcard character |
Description |
Example |
|---|---|---|
% |
Any string of zero or more characters. |
%Name% matches AB Name as well as AB Name CD as well as Name1 %Name% does not math AB Nam CD %Name does not math Name CD |
_ |
Any single character. |
Feature _ matches Feature 1 as well as feature A |
[] |
Any single character within the specified range ([a-f]) or set ([abcdef]). |
Feature [12345] matches Feature 1, Feature 3 but not Feature 9 |
[^] |
Any single character not within the specified range ([^a-f]) or set ([^abcdef]). |
Feature [^A-M] matches Feature M to Feature Z but not Feature A to Feature M |
Table 3: Wildcard characters that can be used with the pattern operator
Performance of string comparison
Under certain circumstance string comparison can be time consuming and for huge amounts of comments. Performance is of course always depending on your system environment the amount of data you have in your system and your overall system load.
When querying huge amounts of comments following hints might help to specify optimal filters:
•Using the like operator with a comparison string that includes wildcard characters needs a full scan of all comments and is therefore O(n) with n being the total number of stored comments for features or observations.
•The Contains and Ends with operators need to scan all comments and are therefore O(n) with n being the total number of stored comments for features or observations.
•The Equal and starts with operators use an indexed query and are therefore O(log n) with n being the total number of stored comments for features or observations.
The system stores the execution time of each view when it evaluates the view members, see view member caching for details.
