add comments

src/Interpreters/ColumnAliasesVisitor.h

@@ -14,8 +14,35 @@ class ASTFunction;
 class ASTIdentifier;
 using DataTypePtr = std::shared_ptr<const IDataType>;
 
-/// Visits AST node to rewrite alias columns in filter query
-/// Currently works only in `KeyCondition` of select query and `required_columns` in `InterpreterSelectQuery.cpp`
+/// Visits AST node to rewrite alias columns in query
+/// Currently works only 3 kind ways below
+
+/// For example:
+//    CREATE TABLE test_table
+//    (
+//     `timestamp` DateTime,
+//     `value` UInt64,
+//     `day` Date ALIAS toDate(timestamp),
+//     `day1` Date ALIAS day + 1,
+//     `day2` Date ALIAS day1 + 1,
+//     `time` DateTime ALIAS timestamp
+//    )ENGINE = MergeTree
+//    PARTITION BY toYYYYMMDD(timestamp)
+//    ORDER BY timestamp SETTINGS index_granularity = 1;
+
+/// 1. Rewrite the filters in query when enable optimize_alias_column_prediction
+///  this could help with `optimize_trivial_count`, Partition Prune in `KeyCondition` and secondary indexes.
+///  eg: select max(value) from  test_table where day2 = today(), filters will be: ((toDate(timestamp) + 1) + 1) = today() .
+
+/// 2. Alias on alias for `required_columns` extracted in `InterpreterSelectQuery.cpp`, it could help get all dependent physical columns for query.
+///  eg: select day2 from test_table.  `required_columns` can got require columns from the tempory rewrited AST `((toDate(timestamp) + 1) + 1)`.
+
+/// 3. Help with `optimize_aggregation_in_order` and `optimize_read_in_order` in `ReadInOrderOptimizer.cpp`:
+///    For queries with alias columns in `orderBy` and `groupBy`, these ASTs will not change.
+///    But we generate tempory asts and generate tempory Actions to get the `InputOrderInfo`
+///  eg: select day1 from test_table order by day1;
+
+
 class ColumnAliasesMatcher
 {
 public:

src/Interpreters/addTypeConversionToAST.h

@@ -2,12 +2,12 @@
 
 #include <common/types.h>
 #include <Parsers/IAST_fwd.h>
-#include <Interpreters/Context.h>
 
 
 namespace DB
 {
-
+class Context;
+class NamesAndTypesList;
 /// It will produce an expression with CAST to get an AST with the required type.
 ASTPtr addTypeConversionToAST(ASTPtr && ast, const String & type_name);
 

src/Storages/ReadInOrderOptimizer.cpp

@@ -139,11 +139,12 @@ InputOrderInfoPtr ReadInOrderOptimizer::getInputOrder(const StorageMetadataPtr &
 
         if (ok)
             order_key_prefix_descr.push_back(required_sort_description[i]);
+        else
+            break;
     }
 
     if (order_key_prefix_descr.empty())
         return {};
-
     return std::make_shared<InputOrderInfo>(std::move(order_key_prefix_descr), read_direction);
 }