Github user paul-rogers commented on a diff in the pull request:
https://github.com/apache/drill/pull/907#discussion_r134034748
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/RegexpUtil.java
---
@@ -96,20 +145,46 @@ public static String sqlToRegexLike(
|| (nextChar == '%')
|| (nextChar == escapeChar)) {
javaPattern.append(nextChar);
+ simplePattern.append(nextChar);
i++;
} else {
throw invalidEscapeSequence(sqlPattern, i);
}
} else if (c == '_') {
+ // if we find _, it is not simple pattern, we are looking for only
%
+ notSimple = true;
javaPattern.append('.');
} else if (c == '%') {
+ if (i == 0) {
+ // % at the start could potentially be one of the simple cases
i.e. ENDS_WITH.
+ endsWith = true;
+ } else if (i == (len-1)) {
--- End diff --
A bit of a funky way to do this. Might was well actually wait to the end.
This is why we need states (as an enum or via recursive descent.) At end:
If all constants: CONST
If one wildcard: one of the simple cases
Otherwise: COMPLEX
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