QL: Simplify the replaceChildren implementations (#66973)

Most of the `Node` transformations calling `Node.replaceChildren`
does not change the size of the children list, hence it is enough to 
check this property once in the `Node` class instead of checking it
in each implementation of the `replaceChildren` method.

Modification:
* All of the tree transformation rules with the exception of the
`Case` and `ArbitraryConditionalFunction` transformations expect the
children count to be the same before and after the transformation, hence
I moved the check for this invariant into the
`final Node.replaceChildrenSameSize(List)` method.
* Removed a few hundred lines from `Node.replaceChildren`
implementations that check the size of the children list
* Switched most of the `replaceChildren()` calls to 
 `replaceChildrenSameSize()` with the exception of the 
 `ArbitraryConditionalFunction` and `Case` Optimizer rules

Author: Andras Palinkas

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/math/ToNumber.java

@@ -107,10 +107,6 @@ public DataType dataType() {
 
     @Override
     public Expression replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() != 2) {
-            throw new IllegalArgumentException("expected [2] children but received [" + newChildren.size() + "]");
-        }
-
         return new ToNumber(source(), newChildren.get(0), newChildren.get(1));
     }
 }

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/math/ToNumberFunctionPipe.java

@@ -27,9 +27,6 @@ public ToNumberFunctionPipe(Source source, Expression expression, Pipe value, Pi
 
     @Override
     public final Pipe replaceChildren(List<Pipe> newChildren) {
-        if (newChildren.size() != 2) {
-            throw new IllegalArgumentException("expected [2] children but received [" + newChildren.size() + "]");
-        }
         return replaceChildren(newChildren.get(0), newChildren.get(1));
     }
 

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/Between.java

@@ -146,10 +146,6 @@ public DataType dataType() {
 
     @Override
     public Expression replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() != 4) {
-            throw new IllegalArgumentException("expected [4] children but received [" + newChildren.size() + "]");
-        }
-
         return new Between(source(), newChildren.get(0), newChildren.get(1), newChildren.get(2), newChildren.get(3));
     }
 }

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/BetweenFunctionPipe.java

@@ -30,9 +30,6 @@ public BetweenFunctionPipe(Source source, Expression expression, Pipe input, Pip
 
     @Override
     public final Pipe replaceChildren(List<Pipe> newChildren) {
-        if (newChildren.size() != 5) {
-            throw new IllegalArgumentException("expected [5] children but received [" + newChildren.size() + "]");
-        }
         return replaceChildren(newChildren.get(0), newChildren.get(1), newChildren.get(2), newChildren.get(3), newChildren.get(4));
     }
 

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/CIDRMatch.java

@@ -134,9 +134,6 @@ public DataType dataType() {
 
     @Override
     public Expression replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() < 2) {
-            throw new IllegalArgumentException("expected at least [2] children but received [" + newChildren.size() + "]");
-        }
         return new CIDRMatch(source(), newChildren.get(0), newChildren.subList(1, newChildren.size()));
     }
 }

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/CIDRMatchFunctionPipe.java

@@ -31,9 +31,6 @@ public CIDRMatchFunctionPipe(Source source, Expression expression, Pipe input, L
 
     @Override
     public final Pipe replaceChildren(List<Pipe> newChildren) {
-        if (newChildren.size() < 2) {
-            throw new IllegalArgumentException("expected at least [2] children but received [" + newChildren.size() + "]");
-        }
         return replaceChildren(newChildren.get(0), newChildren.subList(1, newChildren.size()));
     }
 

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/ConcatFunctionPipe.java

@@ -41,7 +41,7 @@ public final Pipe resolveAttributes(AttributeResolver resolver) {
             return this;
         }
 
-        return replaceChildren(newValues);
+        return replaceChildrenSameSize(newValues);
     }
 
     @Override

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/EndsWith.java

@@ -126,10 +126,6 @@ public DataType dataType() {
 
     @Override
     public Expression replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() != 2) {
-            throw new IllegalArgumentException("expected [2] children but received [" + newChildren.size() + "]");
-        }
-
         return new EndsWith(source(), newChildren.get(0), newChildren.get(1), configuration());
     }
 

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/EndsWithFunctionPipe.java

@@ -29,9 +29,6 @@ public EndsWithFunctionPipe(Source source, Expression expression, Pipe input, Pi
 
     @Override
     public final Pipe replaceChildren(List<Pipe> newChildren) {
-        if (newChildren.size() != 2) {
-            throw new IllegalArgumentException("expected [2] children but received [" + newChildren.size() + "]");
-        }
         return replaceChildren(newChildren.get(0), newChildren.get(1));
     }
 

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/IndexOf.java

@@ -130,10 +130,6 @@ public DataType dataType() {
 
     @Override
     public Expression replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() != 3) {
-            throw new IllegalArgumentException("expected [3] children but received [" + newChildren.size() + "]");
-        }
-
         return new IndexOf(source(), newChildren.get(0), newChildren.get(1), newChildren.get(2), configuration());
     }
 

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/IndexOfFunctionPipe.java

@@ -30,9 +30,6 @@ public IndexOfFunctionPipe(Source source, Expression expression, Pipe input, Pip
 
     @Override
     public final Pipe replaceChildren(List<Pipe> newChildren) {
-        if (newChildren.size() != 3) {
-            throw new IllegalArgumentException("expected [3] children but received [" + newChildren.size() + "]");
-        }
         return replaceChildren(newChildren.get(0), newChildren.get(1), newChildren.get(2));
     }
 

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/Length.java

@@ -96,10 +96,6 @@ public DataType dataType() {
 
     @Override
     public Expression replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() != 1) {
-            throw new IllegalArgumentException("expected [1] children but received [" + newChildren.size() + "]");
-        }
-
         return new Length(source(), newChildren.get(0));
     }
 

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/LengthFunctionPipe.java

@@ -26,9 +26,6 @@ public LengthFunctionPipe(Source source, Expression expression, Pipe input) {
 
     @Override
     public final Pipe replaceChildren(List<Pipe> newChildren) {
-        if (newChildren.size() != 1) {
-            throw new IllegalArgumentException("expected [1] children but received [" + newChildren.size() + "]");
-        }
         return replaceChildren(newChildren.get(0));
     }
 

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/Match.java

@@ -52,9 +52,6 @@ protected NodeInfo<? extends Expression> info() {
 
     @Override
     public Expression replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() < 2) {
-            throw new IllegalArgumentException("expected at least [2] children but received [" + newChildren.size() + "]");
-        }
         return new Match(source(), newChildren);
     }
 

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/StringContains.java

@@ -119,10 +119,6 @@ public DataType dataType() {
 
     @Override
     public Expression replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() != 2) {
-            throw new IllegalArgumentException("expected [2] children but received [" + newChildren.size() + "]");
-        }
-
         return new StringContains(source(), newChildren.get(0), newChildren.get(1), eqlConfiguration());
     }
 

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/StringContainsFunctionPipe.java

@@ -30,9 +30,6 @@ public StringContainsFunctionPipe(Source source, Expression expression, Pipe str
 
     @Override
     public final Pipe replaceChildren(List<Pipe> newChildren) {
-        if (newChildren.size() != 2) {
-            throw new IllegalArgumentException("expected [2] children but received [" + newChildren.size() + "]");
-        }
         return replaceChildren(newChildren.get(0), newChildren.get(1));
     }
 

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/Substring.java

@@ -121,10 +121,6 @@ public DataType dataType() {
 
     @Override
     public Expression replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() != 3) {
-            throw new IllegalArgumentException("expected [3] children but received [" + newChildren.size() + "]");
-        }
-
         return new Substring(source(), newChildren.get(0), newChildren.get(1), newChildren.get(2));
     }
 }

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/SubstringFunctionPipe.java

@@ -28,9 +28,6 @@ public SubstringFunctionPipe(Source source, Expression expression, Pipe input, P
 
     @Override
     public final Pipe replaceChildren(List<Pipe> newChildren) {
-        if (newChildren.size() != 3) {
-            throw new IllegalArgumentException("expected [3] children but received [" + newChildren.size() + "]");
-        }
         return replaceChildren(newChildren.get(0), newChildren.get(1), newChildren.get(2));
     }
 

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/ToString.java

@@ -95,10 +95,6 @@ public DataType dataType() {
 
     @Override
     public Expression replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() != 1) {
-            throw new IllegalArgumentException("expected [1] children but received [" + newChildren.size() + "]");
-        }
-
         return new ToString(source(), newChildren.get(0));
     }
 }

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/ToStringFunctionPipe.java

@@ -26,9 +26,6 @@ public ToStringFunctionPipe(Source source, Expression expression, Pipe input) {
 
     @Override
     public final ToStringFunctionPipe replaceChildren(List<Pipe> newChildren) {
-        if (newChildren.size() != 1) {
-            throw new IllegalArgumentException("expected [1] children but received [" + newChildren.size() + "]");
-        }
         return new ToStringFunctionPipe(source(), expression(), newChildren.get(0));
     }
 

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/Wildcard.java

@@ -49,10 +49,6 @@ protected NodeInfo<? extends Expression> info() {
 
     @Override
     public Expression replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() < 2) {
-            throw new IllegalArgumentException("expected at least [2] children but received [" + newChildren.size() + "]");
-        }
-
         return new Wildcard(source(), newChildren.get(0), newChildren.subList(1, newChildren.size()));
     }
 

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/optimizer/Optimizer.java

@@ -184,7 +184,7 @@ protected LogicalPlan rule(Filter filter) {
                 plan = new Filter(f.source(), f.child(), new And(f.source(), f.condition(), filter.condition()));
             } else if (child instanceof UnaryPlan) {
                 UnaryPlan up = (UnaryPlan) child;
-                plan = child.replaceChildren(singletonList(new Filter(filter.source(), up.child(), filter.condition())));
+                plan = child.replaceChildrenSameSize(singletonList(new Filter(filter.source(), up.child(), filter.condition())));
             }
 
             return plan;
@@ -426,13 +426,13 @@ protected LogicalPlan rule(OrderBy orderBy) {
                         // preserve the order for the base query, everything else needs to be ascending
                         List<Order> pushedOrder = baseFilter ? orderBy.order() : ascendingOrders;
                         OrderBy order = new OrderBy(filter.source(), filter.child(), pushedOrder);
-                        orderedQueries.add((KeyedFilter) filter.replaceChildren(singletonList(order)));
+                        orderedQueries.add((KeyedFilter) filter.replaceChildrenSameSize(singletonList(order)));
                         baseFilter = false;
                     }
 
                     KeyedFilter until = join.until();
                     OrderBy order = new OrderBy(until.source(), until.child(), ascendingOrders);
-                    until = (KeyedFilter) until.replaceChildren(singletonList(order));
+                    until = (KeyedFilter) until.replaceChildrenSameSize(singletonList(order));
 
                     OrderDirection direction = orderBy.order().get(0).direction();
                     plan = join.with(orderedQueries, until, direction);

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/parser/LogicalPlanBuilder.java

@@ -123,7 +123,7 @@ public Object visitStatement(StatementContext ctx) {
                 } else {
                     previous = new Tail(defaultLimitSource, defaultSize, previous);
                 }
-                plan = plan.replaceChildren(singletonList(previous));
+                plan = plan.replaceChildrenSameSize(singletonList(previous));
             }
             previous = plan;
         }

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/plan/logical/Join.java

@@ -6,7 +6,6 @@
 
 package org.elasticsearch.xpack.eql.plan.logical;
 
-import org.elasticsearch.xpack.eql.EqlIllegalArgumentException;
 import org.elasticsearch.xpack.ql.capabilities.Resolvables;
 import org.elasticsearch.xpack.ql.expression.Attribute;
 import org.elasticsearch.xpack.ql.expression.Expressions;
@@ -77,9 +76,6 @@ protected NodeInfo<? extends Join> info() {
 
     @Override
     public Join replaceChildren(List<LogicalPlan> newChildren) {
-        if (newChildren.size() < 2) {
-            throw new EqlIllegalArgumentException("expected at least [2] children but received [{}]", newChildren.size());
-        }
         int lastIndex = newChildren.size() - 1;
         return new Join(source(), newChildren.subList(0, lastIndex), newChildren.get(lastIndex), timestamp, tiebreaker, direction);
     }

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/plan/logical/Sequence.java

@@ -7,7 +7,6 @@
 package org.elasticsearch.xpack.eql.plan.logical;
 
 import org.elasticsearch.common.unit.TimeValue;
-import org.elasticsearch.xpack.eql.EqlIllegalArgumentException;
 import org.elasticsearch.xpack.ql.expression.Attribute;
 import org.elasticsearch.xpack.ql.expression.Order.OrderDirection;
 import org.elasticsearch.xpack.ql.plan.logical.LogicalPlan;
@@ -52,9 +51,6 @@ protected NodeInfo<Sequence> info() {
 
     @Override
     public Join replaceChildren(List<LogicalPlan> newChildren) {
-        if (newChildren.size() < 2) {
-            throw new EqlIllegalArgumentException("expected at least [2] children but received [{}]", newChildren.size());
-        }
         int lastIndex = newChildren.size() - 1;
         return new Sequence(source(), newChildren.subList(0, lastIndex), newChildren.get(lastIndex), maxSpan, timestamp(), tiebreaker(),
                 direction());

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/plan/physical/SequenceExec.java

@@ -8,7 +8,6 @@
 
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.common.unit.TimeValue;
-import org.elasticsearch.xpack.eql.EqlIllegalArgumentException;
 import org.elasticsearch.xpack.eql.execution.assembler.ExecutionManager;
 import org.elasticsearch.xpack.eql.execution.search.Limit;
 import org.elasticsearch.xpack.eql.session.EqlSession;
@@ -72,11 +71,6 @@ protected NodeInfo<SequenceExec> info() {
 
     @Override
     public PhysicalPlan replaceChildren(List<PhysicalPlan> newChildren) {
-        if (newChildren.size() != children().size()) {
-            throw new EqlIllegalArgumentException("Expected the same number of children [{}] but got [{}]",
-                    children().size(),
-                    newChildren.size());
-        }
         return new SequenceExec(source(), newChildren, keys, timestamp, tiebreaker, limit, direction, maxSpan);
     }
 

x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/plan/physical/UnaryExec.java

@@ -23,9 +23,6 @@ protected UnaryExec(Source source, PhysicalPlan child) {
 
     @Override
     public final PhysicalPlan replaceChildren(List<PhysicalPlan> newChildren) {
-        if (newChildren.size() != 1) {
-            throw new IllegalArgumentException("expected [1] child but received [" + newChildren.size() + "]");
-        }
         return replaceChild(newChildren.get(0));
     }
 

x-pack/plugin/eql/src/test/java/org/elasticsearch/xpack/eql/expression/function/scalar/string/ConcatFunctionPipeTests.java

@@ -68,8 +68,8 @@ public void testReplaceChildren() {
         List<Pipe> newValues = mutateOneValue(b.values());
 
         ConcatFunctionPipe newB = new ConcatFunctionPipe(b.source(), b.expression(), b.values());
-        ConcatFunctionPipe transformed = newB.replaceChildren(newValues);
-
+        ConcatFunctionPipe transformed = (ConcatFunctionPipe) newB.replaceChildrenSameSize(newValues);
+        
         assertEquals(transformed.values(), newValues);
         assertEquals(transformed.source(), b.source());
         assertEquals(transformed.expression(), b.expression());

x-pack/plugin/ql/src/main/java/org/elasticsearch/xpack/ql/expression/Alias.java

@@ -57,9 +57,6 @@ protected NodeInfo<Alias> info() {
 
     @Override
     public Expression replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() != 1) {
-            throw new IllegalArgumentException("expected [1] child but received [" + newChildren.size() + "]");
-        }
         return new Alias(source(), name(), qualifier, newChildren.get(0), id(), synthetic());
     }
 

x-pack/plugin/ql/src/main/java/org/elasticsearch/xpack/ql/expression/Order.java

@@ -58,9 +58,6 @@ public DataType dataType() {
 
     @Override
     public Order replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() != 1) {
-            throw new IllegalArgumentException("expected [1] child but received [" + newChildren.size() + "]");
-        }
         return new Order(source(), newChildren.get(0), direction, nulls);
     }
 

x-pack/plugin/ql/src/main/java/org/elasticsearch/xpack/ql/expression/UnaryExpression.java

@@ -24,9 +24,6 @@ protected UnaryExpression(Source source, Expression child) {
 
     @Override
     public final UnaryExpression replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() != 1) {
-            throw new IllegalArgumentException("expected [1] child but received [" + newChildren.size() + "]");
-        }
         return replaceChild(newChildren.get(0));
     }
     protected abstract UnaryExpression replaceChild(Expression newChild);

x-pack/plugin/ql/src/main/java/org/elasticsearch/xpack/ql/expression/UnresolvedAlias.java

@@ -30,9 +30,6 @@ protected NodeInfo<UnresolvedAlias> info() {
 
     @Override
     public Expression replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() != 1) {
-            throw new IllegalArgumentException("expected [1] child but received [" + newChildren.size() + "]");
-        }
         return new UnresolvedAlias(source(), newChildren.get(0));
     }
 

x-pack/plugin/ql/src/main/java/org/elasticsearch/xpack/ql/expression/function/aggregate/Count.java

@@ -35,9 +35,6 @@ protected NodeInfo<Count> info() {
 
     @Override
     public Count replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() != 1) {
-            throw new IllegalArgumentException("expected [1] child but received [" + newChildren.size() + "]");
-        }
         return new Count(source(), newChildren.get(0), distinct);
     }
 

x-pack/plugin/ql/src/main/java/org/elasticsearch/xpack/ql/expression/function/scalar/BinaryScalarFunction.java

@@ -28,9 +28,6 @@ protected BinaryScalarFunction(Source source, Expression left, Expression right)
 
     @Override
     public final BinaryScalarFunction replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() != 2) {
-            throw new IllegalArgumentException("expected [2] children but received [" + newChildren.size() + "]");
-        }
         Expression newLeft = newChildren.get(0);
         Expression newRight = newChildren.get(1);
 

x-pack/plugin/ql/src/main/java/org/elasticsearch/xpack/ql/expression/function/scalar/UnaryScalarFunction.java

@@ -33,9 +33,6 @@ protected UnaryScalarFunction(Source source, Expression field) {
 
     @Override
     public final UnaryScalarFunction replaceChildren(List<Expression> newChildren) {
-        if (newChildren.size() != 1) {
-            throw new IllegalArgumentException("expected [1] child but received [" + newChildren.size() + "]");
-        }
         return replaceChild(newChildren.get(0));
     }