[CALCITE-7267] CHAR_LENGTH function is not support in Oracle

core/src/main/java/org/apache/calcite/sql/dialect/DerbySqlDialect.java

@@ -19,8 +19,7 @@
 import org.apache.calcite.sql.SqlCall;
 import org.apache.calcite.sql.SqlDialect;
 import org.apache.calcite.sql.SqlWriter;
-import org.apache.calcite.sql.fun.SqlLibraryOperators;
-import org.apache.calcite.sql.parser.SqlParserPos;
+import org.apache.calcite.util.RelToSqlConverterUtil;
 
 /**
  * A <code>SqlDialect</code> implementation for the Apache Derby database.
@@ -40,9 +39,7 @@ public DerbySqlDialect(Context context) {
       final int rightPrec) {
     switch (call.getKind()) {
     case CHAR_LENGTH:
-      SqlCall lengthCall = SqlLibraryOperators.LENGTH
-          .createCall(SqlParserPos.ZERO, call.getOperandList());
-      super.unparseCall(writer, lengthCall, leftPrec, rightPrec);
+      RelToSqlConverterUtil.convertCharLengthToLength(writer, call, leftPrec, rightPrec);
       break;
     default:
       super.unparseCall(writer, call, leftPrec, rightPrec);

core/src/main/java/org/apache/calcite/sql/dialect/OracleSqlDialect.java

@@ -38,6 +38,7 @@
 import org.apache.calcite.sql.fun.SqlStdOperatorTable;
 import org.apache.calcite.sql.parser.SqlParserPos;
 import org.apache.calcite.sql.type.SqlTypeName;
+import org.apache.calcite.util.RelToSqlConverterUtil;
 
 import com.google.common.collect.ImmutableList;
 
@@ -196,6 +197,9 @@ public OracleSqlDialect(Context context) {
       }
       writer.endFunCall(frame);
       break;
+    case CHAR_LENGTH:
+      RelToSqlConverterUtil.convertCharLengthToLength(writer, call, leftPrec, rightPrec);
+      break;
     case FLOOR:
       if (call.operandCount() != 2) {
         super.unparseCall(writer, call, leftPrec, rightPrec);

core/src/main/java/org/apache/calcite/sql/dialect/PrestoSqlDialect.java

@@ -37,7 +37,6 @@
 import org.apache.calcite.sql.SqlNode;
 import org.apache.calcite.sql.SqlWriter;
 import org.apache.calcite.sql.fun.SqlArrayValueConstructor;
-import org.apache.calcite.sql.fun.SqlLibraryOperators;
 import org.apache.calcite.sql.fun.SqlMapValueConstructor;
 import org.apache.calcite.sql.fun.SqlStdOperatorTable;
 import org.apache.calcite.sql.parser.SqlParserPos;
@@ -252,9 +251,7 @@ private static void unparseUsingLimit(SqlWriter writer, @Nullable SqlNode offset
         }
         break;
       case CHAR_LENGTH:
-        SqlCall lengthCall = SqlLibraryOperators.LENGTH
-            .createCall(SqlParserPos.ZERO, call.getOperandList());
-        super.unparseCall(writer, lengthCall, leftPrec, rightPrec);
+        RelToSqlConverterUtil.convertCharLengthToLength(writer, call, leftPrec, rightPrec);
         break;
       case TRIM:
         RelToSqlConverterUtil.unparseTrimLR(writer, call, leftPrec, rightPrec);

core/src/main/java/org/apache/calcite/sql/dialect/SnowflakeSqlDialect.java

@@ -28,6 +28,7 @@
 import org.apache.calcite.sql.fun.SqlLibraryOperators;
 import org.apache.calcite.sql.parser.SqlParserPos;
 import org.apache.calcite.sql.type.SqlTypeName;
+import org.apache.calcite.util.RelToSqlConverterUtil;
 
 import org.checkerframework.checker.nullness.qual.Nullable;
 
@@ -62,9 +63,7 @@ public SnowflakeSqlDialect(Context context) {
       super.unparseCall(writer, bitOrCall, leftPrec, rightPrec);
       break;
     case CHAR_LENGTH:
-      SqlCall lengthCall = SqlLibraryOperators.LENGTH
-          .createCall(SqlParserPos.ZERO, call.getOperandList());
-      super.unparseCall(writer, lengthCall, leftPrec, rightPrec);
+      RelToSqlConverterUtil.convertCharLengthToLength(writer, call, leftPrec, rightPrec);
       break;
     case ENDS_WITH:
       SqlCall endsWithCall = SqlLibraryOperators.ENDSWITH

core/src/main/java/org/apache/calcite/sql/dialect/SqliteSqlDialect.java

@@ -21,8 +21,6 @@
 import org.apache.calcite.sql.SqlDialect;
 import org.apache.calcite.sql.SqlNode;
 import org.apache.calcite.sql.SqlWriter;
-import org.apache.calcite.sql.fun.SqlLibraryOperators;
-import org.apache.calcite.sql.parser.SqlParserPos;
 import org.apache.calcite.util.RelToSqlConverterUtil;
 
 import org.checkerframework.checker.nullness.qual.Nullable;
@@ -58,9 +56,7 @@ public SqliteSqlDialect(SqlDialect.Context context) {
       int leftPrec, int rightPrec) {
     switch (call.getKind()) {
     case CHAR_LENGTH:
-      SqlCall lengthCall = SqlLibraryOperators.LENGTH
-          .createCall(SqlParserPos.ZERO, call.getOperandList());
-      super.unparseCall(writer, lengthCall, leftPrec, rightPrec);
+      RelToSqlConverterUtil.convertCharLengthToLength(writer, call, leftPrec, rightPrec);
       break;
     case TRIM:
       RelToSqlConverterUtil.unparseTrimLR(writer, call, leftPrec, rightPrec);

core/src/main/java/org/apache/calcite/util/RelToSqlConverterUtil.java

@@ -34,6 +34,7 @@
 import org.apache.calcite.sql.SqlSpecialOperator;
 import org.apache.calcite.sql.SqlTypeNameSpec;
 import org.apache.calcite.sql.SqlWriter;
+import org.apache.calcite.sql.fun.SqlLibraryOperators;
 import org.apache.calcite.sql.fun.SqlStdOperatorTable;
 import org.apache.calcite.sql.fun.SqlTrimFunction;
 import org.apache.calcite.sql.parser.SqlParserPos;
@@ -78,6 +79,16 @@ public static void unparseHiveTrim(
     }
   }
 
+  /**
+   * Convert CHAR_LENGTH to LENGTH for some Dialects such as Oracle which not support CHAR_LENGTH.
+   */
+  public static void convertCharLengthToLength(SqlWriter writer, SqlCall call, int leftPrec,
+      int rightPrec) {
+    SqlCall lengthCall = SqlLibraryOperators.LENGTH
+        .createCall(SqlParserPos.ZERO, call.getOperandList());
+    lengthCall.getOperator().unparse(writer, lengthCall, leftPrec, rightPrec);
+  }
+
   /**
    * For usage of TRIM(LEADING 'A' FROM 'ABCA') convert to TRIM, LTRIM and RTRIM,
    * can refer to BigQuery and Presto documents:

core/src/test/java/org/apache/calcite/rel/rel2sql/RelToSqlConverterTest.java

@@ -8274,6 +8274,7 @@ private void checkLiteral2(String expression, String expected) {
     final String expected = "SELECT LENGTH(\"brand_name\")\n"
         + "FROM \"foodmart\".\"product\"";
     sql(query)
+        .withOracle().ok(expected)
         .withPresto().ok(expected)
         .withTrino().ok(expected);
   }