wenhuitang commented on a change in pull request #1862: [CALCITE-3864] Add
Implementation for SqlLibraryOperators.CONCAT_FUNCTION in SqlFunctions and
correct the return type inference of SqlLibraryOperators.CONCAT_FUNCTION
URL: https://github.com/apache/calcite/pull/1862#discussion_r397160310
##########
File path:
core/src/main/java/org/apache/calcite/sql/dialect/MysqlSqlDialect.java
##########
@@ -208,12 +212,52 @@ public boolean supportsAliasedValues() {
unparseFloor(writer, call);
break;
-
default:
+ if (call.getOperator() == SqlStdOperatorTable.CONCAT) {
+ unparseConcat(writer, call);
+ break;
+ }
super.unparseCall(writer, call, leftPrec, rightPrec);
}
}
+ /**
+ * Unparses String concatenation operator for Mysql, Mysql uses Concat as
string concatenation
+ * operator when PIPES_AS_CONCAT is not enabled. CONCAT concatenation
characters are used by
+ * default.
+ *
+ * @param writer writer
+ * @param call call
+ */
+ private void unparseConcat(SqlWriter writer, SqlCall call) {
+ List<SqlNode> expandOperandList = new ArrayList<>();
+ expandConcatOperands(call, expandOperandList);
Review comment:
Expand operands for CONCAT, so we can generate CONCAT(`fname`, '_', '_',
`lname`) instead of CONCAT(CONCAT(CONCAT(`fname`, '_'), '_'), `lname`)
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