Explain EXPLAIN ESTIMATE (children 1) SelectWithUnionQuery (children 1) ExpressionList (children 1) SelectQuery (children 3) ExpressionList (children 1) Function count (children 1) ExpressionList TablesInSelectQuery (children 1) TablesInSelectQueryElement (children 1) TableExpression (children 1) TableIdentifier test.hits Function equals (children 1) ExpressionList (children 2) Identifier CounterID Literal UInt64_29103473