[Backport] Fix filtering on boolean values in transformation

core/src/main/java/org/apache/druid/java/util/common/granularity/PeriodGranularity.java

@@ -60,7 +60,7 @@ public PeriodGranularity(
   )
   {
     this.period = Preconditions.checkNotNull(period, "period can't be null!");
-    Preconditions.checkArgument(!Period.ZERO.equals(period), "zero period is not acceptable in QueryGranularity!");
+    Preconditions.checkArgument(!Period.ZERO.equals(period), "zero period is not acceptable in PeriodGranularity!");
     this.chronology = tz == null ? ISOChronology.getInstanceUTC() : ISOChronology.getInstance(tz);
     if (origin == null) {
       // default to origin in given time zone when aligning multi-period granularities

core/src/main/java/org/apache/druid/math/expr/Expr.java

@@ -1287,7 +1287,6 @@ public ExprEval eval(ObjectBinding bindings)
       return ExprEval.of(null);
     }
 
-
     if (leftVal.type() == ExprType.STRING && rightVal.type() == ExprType.STRING) {
       return evalString(leftVal.asString(), rightVal.asString());
     } else if (leftVal.type() == ExprType.LONG && rightVal.type() == ExprType.LONG) {

core/src/main/java/org/apache/druid/math/expr/ExprEval.java

@@ -117,7 +117,7 @@ public static ExprEval bestEffortOf(@Nullable Object val)
   }
 
   // Cached String values
-  private boolean stringValueValid = false;
+  private boolean stringValueCached = false;
   @Nullable
   private String stringValue;
 
@@ -137,17 +137,35 @@ public T value()
     return value;
   }
 
+  void cacheStringValue(@Nullable String value)
+  {
+    stringValue = value;
+    stringValueCached = true;
+  }
+
+  @Nullable
+  String getCachedStringValue()
+  {
+    assert stringValueCached;
+    return stringValue;
+  }
+
+  boolean isStringValueCached()
+  {
+    return stringValueCached;
+  }
+
   @Nullable
   public String asString()
   {
-    if (!stringValueValid) {
+    if (!stringValueCached) {
       if (value == null) {
         stringValue = null;
       } else {
         stringValue = String.valueOf(value);
       }
 
-      stringValueValid = true;
+      stringValueCached = true;
     }
 
     return stringValue;
@@ -567,6 +585,21 @@ private ArrayExprEval(@Nullable T[] value)
       super(value);
     }
 
+    @Override
+    @Nullable
+    public String asString()
+    {
+      if (!isStringValueCached()) {
+        if (value == null) {
+          cacheStringValue(null);
+        } else {
+          cacheStringValue(Arrays.toString(value));
+        }
+      }
+
+      return getCachedStringValue();
+    }
+
     @Override
     public boolean isNumericNull()
     {

processing/src/main/java/org/apache/druid/segment/filter/PredicateValueMatcherFactory.java

@@ -116,11 +116,13 @@ public boolean matches()
           } else if (rowValue instanceof Number) {
             // Double or some other non-int, non-long, non-float number.
             return getDoublePredicate().applyDouble((double) rowValue);
-          } else if (rowValue instanceof String || rowValue instanceof List) {
-            // String or list-of-something. Cast to list of strings and evaluate them as strings.
+          } else {
+            // Other types. Cast to list of strings and evaluate them as strings.
+            // Boolean values are handled here as well since it is not a known type in Druid.
             final List<String> rowValueStrings = Rows.objectToStrings(rowValue);
 
             if (rowValueStrings.isEmpty()) {
+              // Empty list is equivalent to null.
               return getStringPredicate().apply(null);
             }
 
@@ -131,9 +133,6 @@ public boolean matches()
             }
 
             return false;
-          } else {
-            // Unfilterable type. Treat as null.
-            return getStringPredicate().apply(null);
           }
         }
 

processing/src/main/java/org/apache/druid/segment/virtual/ExpressionSelectors.java

@@ -265,7 +265,6 @@ class DefaultExpressionDimensionSelector extends BaseSingleValueDimensionSelecto
           @Override
           protected String getValue()
           {
-
             return NullHandling.emptyToNullIfNeeded(baseSelector.getObject().asString());
           }