Github user sachouche commented on a diff in the pull request:
https://github.com/apache/drill/pull/1001#discussion_r146705325
--- Diff:
exec/java-exec/src/main/codegen/templates/CastFunctionsSrcVarLenTargetVarLen.java
---
@@ -73,6 +73,9 @@ public void eval() {
out.start = in.start;
if (charCount <= length.value || length.value == 0 ) {
out.end = in.end;
+ if (charCount == (out.end - out.start)) {
+ out.asciiMode =
org.apache.drill.exec.expr.holders.VarCharHolder.CHAR_MODE_IS_ASCII; // we can
conclude this string is ASCII
--- End diff --
- As previously stated (when responding to Paul'd comment), the expression
framework is able to use the same VarCharHolder input variable when it is
shared amongst multiple expressions
- If the original column was of type var-binary, then the expression
framework will include a cast to var-char
- The cast logic will also compute the string length
- Using this information to deduce whether the string is pure ASCII or not
- UTF-8 encoding uses 1 byte for ASCII and 2, 3, or 4 for other character
sets
- If the encoded length and character length are equal, then this means
this is an ASCII string
---
