Replace sqrt udf with a call to calcite's power(x, 0.5)

Signed-off-by: Yuanchun Shen <yuanchu@amazon.com>

Author: yuancu

core/src/main/java/org/opensearch/sql/expression/function/PPLBuiltinOperators.java

@@ -51,7 +51,6 @@
 import org.opensearch.sql.expression.function.udf.math.DivideFunction;
 import org.opensearch.sql.expression.function.udf.math.EulerFunction;
 import org.opensearch.sql.expression.function.udf.math.ModFunction;
-import org.opensearch.sql.expression.function.udf.math.SqrtFunction;
 import org.opensearch.sql.expression.function.udf.text.LocateFunction;
 
 /** Defines functions and operators that are implemented only by PPL */
@@ -60,7 +59,6 @@ public class PPLBuiltinOperators extends ReflectiveSqlOperatorTable {
   // Math functions
   public static final SqlOperator SPAN = new SpanFunctionImpl().toUDF("SPAN");
   public static final SqlOperator E = new EulerFunction().toUDF("E");
-  public static final SqlOperator SQRT = new SqrtFunction().toUDF("SQRT");
   public static final SqlOperator CONV = new ConvFunction().toUDF("CONVERT");
   public static final SqlOperator MOD = new ModFunction().toUDF("MOD");
   public static final SqlOperator CRC32 = new CRC32Function().toUDF("CRC32");

core/src/main/java/org/opensearch/sql/expression/function/PPLFuncImpTable.java

@@ -218,10 +218,6 @@ void populate() {
       // Register PPL UDF operator
       registerOperator(SPAN, PPLBuiltinOperators.SPAN);
       registerOperator(E, PPLBuiltinOperators.E);
-
-      // SqlStdOperatorTable.SQRT is declared but not implemented, therefore we use a custom
-      // implementation.
-      registerOperator(SQRT, PPLBuiltinOperators.SQRT);
       registerOperator(CONV, PPLBuiltinOperators.CONV);
       registerOperator(MOD, PPLBuiltinOperators.MOD);
       registerOperator(MODULUS, PPLBuiltinOperators.MOD);
@@ -347,6 +343,16 @@ void populate() {
                       SqlLibraryOperators.LOG,
                       arg,
                       builder.makeApproxLiteral(BigDecimal.valueOf(Math.E)))));
+      // SqlStdOperatorTable.SQRT is declared but not implemented. The call to SQRT in Calcite is
+      // converted to POWER(x, 0.5).
+      register(
+          SQRT,
+          ((FunctionImp1)
+              (builder, arg) ->
+                  builder.makeCall(
+                      SqlStdOperatorTable.POWER,
+                      arg,
+                      builder.makeApproxLiteral(BigDecimal.valueOf(0.5)))));
       register(
           TYPEOF,
           (FunctionImp1)