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https://issues.apache.org/jira/browse/CASSANDRA-17190?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17461625#comment-17461625
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Manish Ghildiyal commented on CASSANDRA-17190:
----------------------------------------------
I have added a method to StringType
{code:java}
public abstract String charsetName();{code}
Different specific types of StringType would return the value accordingly, like
ASCIIType returns "US-ASCII". This way I don't need to add function for each
combination (ascii/ascii, ascii/text, text/ascii and text/text) in
OperationFcts. I just added:
{code:java}
protected ByteBuffer excuteOnStrings(StringType resultType,
StringType leftType,
ByteBuffer left,
StringType rightType,
ByteBuffer right) throws UnsupportedEncodingException
{
throw new UnsupportedOperationException();
}{code}
..and corresponding OPERATION
{code:java}
CONCATENATION('+', "_concat")
{
@Override
protected ByteBuffer executeOnNumerics(NumberType<?> resultType, NumberType<?>
leftType, ByteBuffer left, NumberType<?> rightType, ByteBuffer right) {
//TODO: not sure what goes here
}
@Override
protected ByteBuffer excuteOnStrings(StringType resultType,
StringType leftType,
ByteBuffer left,
StringType rightType,
ByteBuffer right) throws UnsupportedEncodingException {
return resultType.concat(leftType, left, rightType, right);
}
};{code}
If this is correct approach, would add another OPERATION for '-' too.
An example of CSQL query would also help.
> Add support for String contatenation through the "+" operator
> -------------------------------------------------------------
>
> Key: CASSANDRA-17190
> URL: https://issues.apache.org/jira/browse/CASSANDRA-17190
> Project: Cassandra
> Issue Type: Improvement
> Components: CQL/Interpreter
> Reporter: Benjamin Lerer
> Assignee: Manish Ghildiyal
> Priority: Normal
> Labels: AdventCalendar2021, lhf
> Fix For: 4.x
>
>
> Since 4.0, Cassandra support operations on numeric types and on some temporal
> types.
> We should add support for string concatenations through the {{+}} operator.
> +Additional information for newcomers:+
> Cassandra has 2 string types: {{Text}} ({{UTF8Type}}) and ascii
> ({{AsciiType}}) both are sub-classes of ({{StringType}}). In order to add
> support for string concatenation you will need to add a new method to
> {{StringType}} and modify {{OperationFcts}} to add the new functions (one for
> each combination of types: ascii/ascii, ascii/text, text/ascii and text/text).
> The unit test should be added to {{OperationFctsTest}}.
> To allow for concatenating constants (eg: SELECT v1 + ' ' + v2 FROM ...) you
> will need to add a {{getPreferedTypeFor}} method to
> {{org.apache.cassandra.Constants.Type.STRING}} that determine the constant
> type based on its content (ascii or not).
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