The OWA_PATTERN package provides an interface to locate text patterns within strings and replace the matched string with another string.
See Also:
For more information about implementation of this package:The chapter contains the following topics:
Types
Operational Notes
You can use a pattern as both an input and output parameter. Thus, you can pass the same regular expression to OWA_PATTERN function calls, and it only has to be parsed once.
OWA_PATTERN.PATTERN
The OWA_PATTERN subprograms are overloaded. Specifically, there are six versions of MATCH, and four each of AMATCH and CHANGE. The subprograms use the following parameters:
line - This is the target to be examined for a match. It can be more than one line of text or a owa_text.multi_line data type.
pat - This is the pattern that the subprograms attempt to locate in line. The pattern can contain regular expressions. In the owa_pattern.change function and procedure, this parameter is called from_str.
flags - This specifies whether the search is case-sensitive or if substitutions are done globally.
Use regular expressions with the subprograms in this package. You Specify a regular expression by creating the string you want to match interspersed with various wildcard tokens and quantifiers.
Wildcard tokens match something other than themselves:
Table 192-1 Wildcard tokens recognized by OWA_PATTERN package
| Token | Description |
|---|---|
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Matches newline or the beginning of the target |
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Matches newline or the end of the target |
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Matches newline |
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Matches any character except newline |
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Matches tab |
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Matches digits [0-9] |
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Matches non-digits [not 0-9] |
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Matches word characters (0-9, a-z, A-Z, or _) |
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Matches non-word characters (not 0-9, a-z, A-Z, or _) |
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Matches whitespace characters (blank, tab, or newline). |
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Matches non-whitespace characters (not blank, tab, or newline) |
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Matches "word" boundaries (between \w and \W) |
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Matches the value in the current character set of the two hexadecimal digits |
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Matches the value in the current character set of the two or three octal digits |
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Followed by any character not covered by another case matches that character |
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Applies only to |
Any tokens except & can have their meaning extended by any of the following quantifiers. You can also apply these quantifiers to literals:
Table 192-4 OWA_PATTERN Package Subprograms
| Subprogram | Description |
|---|---|
|
Determines if a string contains the specified pattern. It lets you specify where in the string the match has to occur |
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Replaces a pattern within a string. If you call it as a function it returns the number of times the regular expression was found and replaced |
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Generates a pattern data type from a |
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Determines if a string contains the specified pattern |
This function specifies if a pattern occurs in a particular location in a string. There are four versions to this function:
The first and second versions of the function do not save the matched tokens (these are saved in the backrefs parameters in the third and fourth versions). The difference between the first and second versions is the pat parameter, which can be a VARCHAR2 or a pattern data type.
The third and fourth versions of the function save the matched tokens in the backrefs parameter. The difference between the third and fourth versions is the pat parameter, which can be a VARCHAR2 or a pattern data type.
Note:
If multiple overlapping strings match the regular expression, this function takes the longest match.OWA_PATTERN.AMATCH( line IN VARCHAR2, from_loc IN INTEGER, pat IN VARCHAR2, flags IN VARCHAR2 DEFAULT NULL) RETURN INTEGER; OWA_PATTERN.AMATCH( line IN VARCHAR2, from_loc IN INTEGER, pat IN OUT PATTERN, flags IN VARCHAR2 DEFAULT NULL) RETURN INTEGER; OWA_PATTERN.AMATCH( line IN VARCHAR2 from_loc IN INTEGER pat in varchar2 backrefs OUT owa_text.vc_arr flags IN VARCHAR2 DEFAULT NULL) RETURN INTEGER; OWA_PATTERN.AMATCH( line IN VARCHAR2 from_loc IN INTEGER pat IN OUT PATTERN backrefs OUT owa_text.vc_arr flags IN VARCHAR2 DEFAULT NULL) RETURN INTEGER;
Table 192-5 AMATCH Function Parameters
| Parameter | Description |
|---|---|
|
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The text to search in. |
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from_loc |
The location (in number of characters) in |
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The string to match. It can contain regular expressions. This can be either a |
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backrefs |
The text that is matched. Each token that is matched is placed in a cell in the |
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flags |
Whether or not the search is case-sensitive. If the value of this parameter is "i", the search is case-insensitive. Otherwise the search is case-sensitive. |
This function or procedure searches and replaces a string or multi_line data type. If multiple overlapping strings match the regular expression, this subprogram takes the longest match.
OWA_PATTERN.CHANGE( line IN OUT VARCHAR2, from_str IN VARCHAR2, to_str IN VARCHAR2, flags IN VARCHAR2 DEFAULT NULL) RETURN INTEGER; OWA_PATTERN.CHANGE( line IN OUT VARCHAR2, from_str IN VARCHAR2, to_str IN VARCHAR2, flags IN VARCHAR2 DEFAULT NULL); owa_pattern.change( mline IN OUT owa_text.multi_line, from_str IN VARCHAR2, to_str IN VARCHAR2, flags IN VARCHAR2 DEFAULT NULL) RETURN INTEGER; OWA_PATTERN.CHANGE( mline IN OUT owa_text.multi_line, from_str IN VARCHAR2, to_str IN VARCHAR2, flags IN VARCHAR2 DEFAULT NULL);
Table 192-6 CHANGE Procedure Parameters
| Parameter | Description |
|---|---|
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The text to search in. The output value of this parameter is the altered string. |
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mline |
The text to search in. This is a |
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The regular expression to replace. |
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to_str |
The substitution pattern. |
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flags |
Whether or not the search is case-sensitive, and whether or not changes are to be made globally. If " |
As a function, it returns the number of substitutions made. If the flag "g" is not used, this number can only be 0 or 1 and only the first match is replaced. The flag "g" specifies to replace all matches with the regular expression.
OWA_PATTERN.CHANGE('Cats in pajamas', 'C.+in', '& red ')
The regular expression matches the substring "Cats in". It then replaces this string with "& red". The ampersand character "&" indicates "Cats in" because that is what matched the regular expression. Thus, this procedure replaces the string "Cats in pajamas" with "Cats in red" If you call this as a function instead of a procedure, the value returned is 1, indicating that a single substitution has been made.
Example 2:
CREATE OR REPLACE PROCEDURE test_pattern as theline VARCHAR2(256);
num_found INTEGER;
BEGIN
theline := 'what is the goal?';
num_found := OWA_PATTERN.CHANGE(theline, 'goal', 'idea', 'g');
HTP.PRINT(num_found); -- num_found is 1
HTP.PRINT(theline); -- theline is 'what is the idea?'
END;
/
SHOW ERRORS
This function determines if a string contains the specified pattern. The pattern can contain regular expressions. If multiple overlapping strings can match the regular expression, this function takes the longest match.
owa_pattern.match( line IN VARCHAR2, pat IN VARCHAR2, flags IN VARCHAR2 DEFAULT NULL) RETURN BOOLEAN; owa_pattern.match( line IN VARCHAR2, pat IN OUT PATTERN, flags IN VARCHAR2 DEFAULT NULL) RETURN BOOLEAN; owa_pattern.match( line IN VARCHAR2, pat IN VARCHAR2, backrefs OUT owa_text.vc_arr, flags IN VARCHAR2 DEFAULT NULL) RETURN BOOLEAN; OWA_PATTERN.MATCH( line IN VARCHAR2, pat IN OUT PATTERN, backrefs OUT owa_text.vc_arr, flags IN VARCHAR2 DEFAULT NULL) RETURN BOOLEAN; owa_pattern.match( mline IN owa_text.multi_line, pat IN VARCHAR2, rlist OUT owa_text.row_list, flags IN VARCHAR2 DEFAULT NULL) RETURN BOOLEAN; OWA_PATTERN.MATCH( mline IN owa_text.multi_line, pat IN OUT pattern, rlist OUT owa_text.row_list, flags IN VARCHAR2 DEFAULT NULL) RETURN BOOLEAN;
Table 192-8 MATCH Function Parameters
| Parameter | Description |
|---|---|
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The line to search in. |
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The text to search in. This is a |
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The pattern to match. This is either a |
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The text that is matched. Each token that is matched is placed in a cell in the |
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An output parameter containing a list of matches. |
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Whether or not the search is case-sensitive. If the value of this parameter is "i", the search is case-insensitive. Otherwise the search is case-sensitive. |
KAZOO is the target where it is searching for the zoo.* regular expression. The period indicates any character other than newline, and the asterisk matches 0 or more of the preceding characters. In this case, it matches any character other than the newline.
Therefore, this regular expression specifies that a matching target consists of zoo, followed by any set of characters neither ending in nor including a newline (which does not match the period). The i flag indicates to ignore case in the search. In this case, the function returns TRUE, which indicates that a match had been found.
boolean foundMatch;
foundMatch := owa_pattern.match('KAZOO', 'zoo.*', 'i');
The following example searches for the string "goal" followed by any number of characters in sometext. If found,
sometext VARCHAR2(256);
pat VARCHAR2(256);
sometext := 'what is the goal?'
pat := 'goal.*';
IF OWA_PATTERN.MATCH(sometext, pat)
THEN
HTP.PRINT('Match found');
ELSE
HTP.PRINT('Match not found');
END IF;
The regular expression in this function can be either a VARCHAR2 or an OWA_PATTERN.PATTERN DATA TYPE. Create AN OWA_PATTERN.PATTERN DATA TYPE from a string using the OWA_PATTERN.GETPAT procedure.
Create a MULTI_LINE DATA TYPE from a long string using the OWA_TEXT.STREAM2MULTI procedure. If a multi_line is used, the rlist parameter specifies a list of chunks where matches were found.
If the line is a string and not a multi_line, you can add an optional output parameter called backrefs. This parameter is a row_list that holds each string in the target that was matched by a sequence of tokens in the regular expression.