[Fix](Variant) support view for accessing variant subcolumns and temp… (#32225)

fe/fe-core/src/main/java/org/apache/doris/analysis/BinaryPredicate.java

@@ -492,17 +492,24 @@ public class BinaryPredicate extends Predicate implements Writable {
             }
         }
 
-        if ((t1.isDecimalV3Type() && !t2.isStringType() && !t2.isFloatingPointType())
-                || (t2.isDecimalV3Type() && !t1.isStringType() && !t1.isFloatingPointType())) {
+        if ((t1.isDecimalV3Type() && !t2.isStringType() && !t2.isFloatingPointType() && !t2.isVariantType())
+                || (t2.isDecimalV3Type() && !t1.isStringType() && !t1.isFloatingPointType() && !t1.isVariantType())) {
             return Type.getAssignmentCompatibleType(getChild(0).getType(), getChild(1).getType(), false,
                     SessionVariable.getEnableDecimal256());
         }
 
         // Variant can be implicit cast to numeric type and string type at present
         if (t1.isVariantType() && (t2.isNumericType() || t2.isStringType())) {
+            if (t2.isDecimalV2Type() || t2.isDecimalV3Type()) {
+                // TODO support decimal
+                return Type.DOUBLE;
+            }
             return Type.fromPrimitiveType(t2);
         }
         if (t2.isVariantType() && (t1.isNumericType() || t1.isStringType())) {
+            if (t1.isDecimalV2Type() || t1.isDecimalV3Type()) {
+                return Type.DOUBLE;
+            }
             return Type.fromPrimitiveType(t1);
         }
 

fe/fe-core/src/main/java/org/apache/doris/nereids/rules/analysis/ExpressionAnalyzer.java

@@ -114,6 +114,12 @@ public class ExpressionAnalyzer extends SubExprAnalyzer<ExpressionRewriteContext
     private final boolean bindSlotInOuterScope;
     private boolean currentInLambda;
 
+    // Keep track of which element_at function's level
+    // e.g. element_at(element_at(v, 'repo'), 'name') level 1
+    //      element_at(v, 'repo') level 2
+    // Only works with function ElementAt which satisfy condition PushDownToProjectionFunction.validToPushDown
+    private int currentElementAtLevel = 0;
+
     public ExpressionAnalyzer(Plan currentPlan, Scope scope, CascadesContext cascadesContext,
             boolean enableExactMatch, boolean bindSlotInOuterScope) {
         super(scope, cascadesContext);
@@ -285,6 +291,9 @@ public class ExpressionAnalyzer extends SubExprAnalyzer<ExpressionRewriteContext
      * ******************************************************************************************** */
     @Override
     public Expression visitUnboundFunction(UnboundFunction unboundFunction, ExpressionRewriteContext context) {
+        if (unboundFunction.getName().equalsIgnoreCase("element_at")) {
+            ++currentElementAtLevel;
+        }
         if (unboundFunction.isHighOrder()) {
             unboundFunction = bindHighOrderFunction(unboundFunction, context);
         } else {
@@ -331,6 +340,17 @@ public class ExpressionAnalyzer extends SubExprAnalyzer<ExpressionRewriteContext
                 // so wrap COUNT with Nvl to ensure it's result is 0 instead of null to get the correct result
                 boundFunction = new Nvl(boundFunction, new BigIntLiteral(0));
             }
+
+            if (currentElementAtLevel == 1
+                    && PushDownToProjectionFunction.validToPushDown(boundFunction)) {
+                // Only rewrite the top level of PushDownToProjectionFunction, otherwise invalid slot will be generated
+                // currentElementAtLevel == 1 means at the top of element_at function, other levels will be ignored.
+                currentElementAtLevel = 0;
+                return visitElementAt((ElementAt) boundFunction, context);
+            }
+            if (boundFunction instanceof ElementAt) {
+                --currentElementAtLevel;
+            }
             return boundFunction;
         }
     }

fe/fe-core/src/main/java/org/apache/doris/nereids/rules/expression/rules/FunctionBinder.java

@@ -80,6 +80,12 @@ public class FunctionBinder extends AbstractExpressionRewriteRule {
 
     public static final FunctionBinder INSTANCE = new FunctionBinder();
 
+    // Keep track of which element_at function's level
+    // e.g. element_at(element_at(v, 'repo'), 'name') level 1
+    //      element_at(v, 'repo') level 2
+    // Only works with function ElementAt which satisfy condition PushDownToProjectionFunction.validToPushDown
+    private int currentElementAtLevel = 0;
+
     @Override
     public Expression visit(Expression expr, ExpressionRewriteContext context) {
         expr = super.visit(expr, context);
@@ -141,6 +147,9 @@ public class FunctionBinder extends AbstractExpressionRewriteRule {
 
     @Override
     public Expression visitUnboundFunction(UnboundFunction unboundFunction, ExpressionRewriteContext context) {
+        if (unboundFunction.getName().equalsIgnoreCase("element_at")) {
+            ++currentElementAtLevel;
+        }
         if (unboundFunction.isHighOrder()) {
             unboundFunction = bindHighOrderFunction(unboundFunction, context);
         } else {
@@ -188,6 +197,16 @@ public class FunctionBinder extends AbstractExpressionRewriteRule {
                 // so wrap COUNT with Nvl to ensure it's result is 0 instead of null to get the correct result
                 boundFunction = new Nvl(boundFunction, new BigIntLiteral(0));
             }
+            if (currentElementAtLevel == 1
+                    && PushDownToProjectionFunction.validToPushDown(boundFunction)) {
+                // Only rewrite the top level of PushDownToProjectionFunction, otherwise invalid slot will be generated
+                // currentElementAtLevel == 1 means at the top of element_at function, other levels will be ignored.
+                currentElementAtLevel = 0;
+                return visitElementAt((ElementAt) boundFunction, context);
+            }
+            if (boundFunction instanceof ElementAt) {
+                --currentElementAtLevel;
+            }
             return boundFunction;
         }
     }
@@ -201,6 +220,7 @@ public class FunctionBinder extends AbstractExpressionRewriteRule {
     @Override
     public Expression visitElementAt(ElementAt elementAt, ExpressionRewriteContext context) {
         Expression boundFunction = visitBoundFunction(elementAt, context);
+
         if (PushDownToProjectionFunction.validToPushDown(boundFunction)) {
             if (ConnectContext.get() != null
                     && ConnectContext.get().getSessionVariable() != null

fe/fe-core/src/main/java/org/apache/doris/nereids/util/TypeCoercionUtils.java

@@ -1294,9 +1294,17 @@ public class TypeCoercionUtils {
 
         // variant type
         if ((leftType.isVariantType() && (rightType.isStringLikeType() || rightType.isNumericType()))) {
+            if (rightType.isDecimalLikeType()) {
+                // TODO support decimal
+                return Optional.of(DoubleType.INSTANCE);
+            }
             return Optional.of(rightType);
         }
         if ((rightType.isVariantType() && (leftType.isStringLikeType() || leftType.isNumericType()))) {
+            if (leftType.isDecimalLikeType()) {
+                // TODO support decimal
+                return Optional.of(DoubleType.INSTANCE);
+            }
             return Optional.of(leftType);
         }
         return Optional.of(DoubleType.INSTANCE);