Interpolate feature

docs/en/sql-reference/statements/select/index.md

@@ -22,7 +22,7 @@ SELECT [DISTINCT [ON (column1, column2, ...)]] expr_list
 [WHERE expr]
 [GROUP BY expr_list] [WITH ROLLUP|WITH CUBE] [WITH TOTALS]
 [HAVING expr]
-[ORDER BY expr_list] [WITH FILL] [FROM expr] [TO expr] [STEP expr]
+[ORDER BY expr_list] [WITH FILL] [FROM expr] [TO expr] [STEP expr] [INTERPOLATE (expr_list)]
 [LIMIT [offset_value, ]n BY columns]
 [LIMIT [n, ]m] [WITH TIES]
 [SETTINGS ...]

docs/en/sql-reference/statements/select/order-by.md

@@ -280,13 +280,15 @@ To fill multiple columns, add `WITH FILL` modifier with optional parameters afte
 
 ``` sql
 ORDER BY expr [WITH FILL] [FROM const_expr] [TO const_expr] [STEP const_numeric_expr], ... exprN [WITH FILL] [FROM expr] [TO expr] [STEP numeric_expr]
+[INTERPOLATE (col AS expr, ... colN AS exprN)]
 ```
 
 `WITH FILL` can be applied for fields with Numeric (all kinds of float, decimal, int) or Date/DateTime types. When applied for `String` fields, missed values are filled with empty strings.
 When `FROM const_expr` not defined sequence of filling use minimal `expr` field value from `ORDER BY`.
 When `TO const_expr` not defined sequence of filling use maximum `expr` field value from `ORDER BY`.
 When `STEP const_numeric_expr` defined then `const_numeric_expr` interprets `as is` for numeric types, as `days` for Date type, as `seconds` for DateTime type. It also supports [INTERVAL](https://clickhouse.com/docs/en/sql-reference/data-types/special-data-types/interval/) data type representing time and date intervals.
 When `STEP const_numeric_expr` omitted then sequence of filling use `1.0` for numeric type, `1 day` for Date type and `1 second` for DateTime type.
+`INTERPOLATE` can be applied to columns not participating in `ORDER BY WITH FILL`. Such columns are filled based on previous field value by applying `expr`.
 
 Example of a query without `WITH FILL`:
 
@@ -483,4 +485,62 @@ Result:
 └────────────┴────────────┴──────────┘
 ```
 
+Example of a query without `INTERPOLATE`:
+
+``` sql
+SELECT n, source, inter FROM (
+   SELECT toFloat32(number % 10) AS n, 'original' AS source, number as inter
+   FROM numbers(10) WHERE number % 3 = 1
+) ORDER BY n WITH FILL FROM 0 TO 5.51 STEP 0.5;
+```
+
+Result:
+
+``` text
+┌───n─┬─source───┬─inter─┐
+│   0 │          │     0 │
+│ 0.5 │          │     0 │
+│   1 │ original │     1 │
+│ 1.5 │          │     0 │
+│   2 │          │     0 │
+│ 2.5 │          │     0 │
+│   3 │          │     0 │
+│ 3.5 │          │     0 │
+│   4 │ original │     4 │
+│ 4.5 │          │     0 │
+│   5 │          │     0 │
+│ 5.5 │          │     0 │
+│   7 │ original │     7 │
+└─────┴──────────┴───────┘
+```
+
+Same query after applying `INTERPOLATE`:
+
+``` sql
+SELECT n, source, inter FROM (
+   SELECT toFloat32(number % 10) AS n, 'original' AS source, number as inter
+   FROM numbers(10) WHERE number % 3 = 1
+) ORDER BY n WITH FILL FROM 0 TO 5.51 STEP 0.5 INTERPOLATE (inter AS inter + 1);
+```
+
+Result:
+
+``` text
+┌───n─┬─source───┬─inter─┐
+│   0 │          │     0 │
+│ 0.5 │          │     0 │
+│   1 │ original │     1 │
+│ 1.5 │          │     2 │
+│   2 │          │     3 │
+│ 2.5 │          │     4 │
+│   3 │          │     5 │
+│ 3.5 │          │     6 │
+│   4 │ original │     4 │
+│ 4.5 │          │     5 │
+│   5 │          │     6 │
+│ 5.5 │          │     7 │
+│   7 │ original │     7 │
+└─────┴──────────┴───────┘
+```
+
 [Original article](https://clickhouse.com/docs/en/sql-reference/statements/select/order-by/) <!--hide-->

docs/ru/sql-reference/statements/select/index.md

@@ -20,7 +20,7 @@ SELECT [DISTINCT [ON (column1, column2, ...)]] expr_list
 [WHERE expr]
 [GROUP BY expr_list] [WITH ROLLUP|WITH CUBE] [WITH TOTALS]
 [HAVING expr]
-[ORDER BY expr_list] [WITH FILL] [FROM expr] [TO expr] [STEP expr]
+[ORDER BY expr_list] [WITH FILL] [FROM expr] [TO expr] [STEP expr] [INTERPOLATE (expr_list)]
 [LIMIT [offset_value, ]n BY columns]
 [LIMIT [n, ]m] [WITH TIES]
 [SETTINGS ...]

docs/ru/sql-reference/statements/select/order-by.md

@@ -280,6 +280,7 @@ SELECT * FROM collate_test ORDER BY s ASC COLLATE 'en';
 
 ```sql
 ORDER BY expr [WITH FILL] [FROM const_expr] [TO const_expr] [STEP const_numeric_expr], ... exprN [WITH FILL] [FROM expr] [TO expr] [STEP numeric_expr]
+[INTERPOLATE (col AS expr, ... colN AS exprN)]
 ```
 
 `WITH FILL` может быть применен к полям с числовыми (все разновидности float, int, decimal) или временными (все разновидности Date, DateTime) типами. В случае применения к полям типа `String` недостающие значения заполняются пустой строкой.
@@ -289,6 +290,8 @@ ORDER BY expr [WITH FILL] [FROM const_expr] [TO const_expr] [STEP const_numeric_
 
 Когда `STEP const_numeric_expr` не указан, тогда используется `1.0` для числовых типов, `1 день` для типа Date и `1 секунда` для типа DateTime.
 
+`INTERPOLATE` может быть применен к колонкам, не участвующим в `ORDER BY WITH FILL`. Такие колонки заполняются значениями, вычисляемыми применением `expr` к предыдущему значению.
+
 Пример запроса без использования `WITH FILL`:
 ```sql
 SELECT n, source FROM (
@@ -395,3 +398,58 @@ ORDER BY
 │ 1970-03-12 │ 1970-01-08 │ original │
 └────────────┴────────────┴──────────┘
 ```
+
+Пример запроса без `INTERPOLATE`:
+
+``` sql
+SELECT n, source, inter FROM (
+   SELECT toFloat32(number % 10) AS n, 'original' AS source, number as inter
+   FROM numbers(10) WHERE number % 3 = 1
+) ORDER BY n WITH FILL FROM 0 TO 5.51 STEP 0.5;
+```
+
+Результат:
+``` text
+┌───n─┬─source───┬─inter─┐
+│   0 │          │     0 │
+│ 0.5 │          │     0 │
+│   1 │ original │     1 │
+│ 1.5 │          │     0 │
+│   2 │          │     0 │
+│ 2.5 │          │     0 │
+│   3 │          │     0 │
+│ 3.5 │          │     0 │
+│   4 │ original │     4 │
+│ 4.5 │          │     0 │
+│   5 │          │     0 │
+│ 5.5 │          │     0 │
+│   7 │ original │     7 │
+└─────┴──────────┴───────┘
+```
+
+Тот же запрос с `INTERPOLATE`:
+
+``` sql
+SELECT n, source, inter FROM (
+   SELECT toFloat32(number % 10) AS n, 'original' AS source, number as inter
+   FROM numbers(10) WHERE number % 3 = 1
+) ORDER BY n WITH FILL FROM 0 TO 5.51 STEP 0.5 INTERPOLATE (inter AS inter + 1);
+```
+
+Результат:
+``` text
+┌───n─┬─source───┬─inter─┐
+│   0 │          │     0 │
+│ 0.5 │          │     0 │
+│   1 │ original │     1 │
+│ 1.5 │          │     2 │
+│   2 │          │     3 │
+│ 2.5 │          │     4 │
+│   3 │          │     5 │
+│ 3.5 │          │     6 │
+│   4 │ original │     4 │
+│ 4.5 │          │     5 │
+│   5 │          │     6 │
+│ 5.5 │          │     7 │
+│   7 │ original │     7 │
+└─────┴──────────┴───────┘

src/Core/InterpolateDescription.cpp

@@ -0,0 +1,63 @@
+#include <Core/Block.h>
+#include <IO/Operators.h>
+#include <Common/JSONBuilder.h>
+#include <Core/InterpolateDescription.h>
+#include <Interpreters/convertFieldToType.h>
+
+namespace DB
+{
+
+void dumpInterpolateDescription(const InterpolateDescription & description, const Block & /*header*/, WriteBuffer & out)
+{
+    bool first = true;
+
+    for (const auto & desc : description)
+    {
+        if (!first)
+            out << ", ";
+        first = false;
+
+        if (desc.column.name.empty())
+            out << "?";
+        else
+            out << desc.column.name;
+    }
+}
+
+void InterpolateColumnDescription::interpolate(Field & field) const
+{
+    if (field.isNull())
+        return;
+    Block expr_columns;
+    Field column_field = convertFieldToType(field, *column.type.get());
+    expr_columns.insert({column.type->createColumnConst(1, column_field), column.type, column.name});
+    actions->execute(expr_columns);
+    field = convertFieldToType((*expr_columns.getByPosition(0).column)[0], *column.type.get());
+}
+
+void InterpolateColumnDescription::explain(JSONBuilder::JSONMap & map, const Block & /*header*/) const
+{
+    map.add("Column", column.name);
+}
+
+std::string dumpInterpolateDescription(const InterpolateDescription & description)
+{
+    WriteBufferFromOwnString wb;
+    dumpInterpolateDescription(description, Block{}, wb);
+    return wb.str();
+}
+
+JSONBuilder::ItemPtr explainInterpolateDescription(const InterpolateDescription & description, const Block & header)
+{
+    auto json_array = std::make_unique<JSONBuilder::JSONArray>();
+    for (const auto & descr : description)
+    {
+        auto json_map = std::make_unique<JSONBuilder::JSONMap>();
+        descr.explain(*json_map, header);
+        json_array->add(std::move(json_map));
+    }
+
+    return json_array;
+}
+
+}

src/Core/InterpolateDescription.h

@@ -0,0 +1,70 @@
+#pragma once
+
+#include <vector>
+#include <memory>
+#include <cstddef>
+#include <string>
+#include <Core/Field.h>
+#include <Core/SettingsEnums.h>
+#include <Common/IntervalKind.h>
+#include <Parsers/ASTOrderByElement.h>
+#include <Parsers/ASTInterpolateElement.h>
+#include <Functions/FunctionsMiscellaneous.h>
+
+class Collator;
+
+namespace DB
+{
+
+namespace JSONBuilder
+{
+    class JSONMap;
+    class IItem;
+    using ItemPtr = std::unique_ptr<IItem>;
+}
+
+class Block;
+
+
+/// Interpolate description
+struct InterpolateColumnDescription
+{
+    using Signature = ExecutableFunctionExpression::Signature;
+
+    ColumnWithTypeAndName column;
+    ExpressionActionsPtr actions;
+
+    explicit InterpolateColumnDescription(const ColumnWithTypeAndName & column_, ExpressionActionsPtr actions_) :
+        column(column_), actions(actions_) {}
+
+    bool operator == (const InterpolateColumnDescription & other) const
+    {
+        return column == other.column;
+    }
+
+    bool operator != (const InterpolateColumnDescription & other) const
+    {
+        return !(*this == other);
+    }
+
+    void interpolate(Field & field) const;
+
+    std::string dump() const
+    {
+        return fmt::format("{}", column.name);
+    }
+
+    void explain(JSONBuilder::JSONMap & map, const Block & header) const;
+};
+
+/// Description of interpolation for several columns.
+using InterpolateDescription = std::vector<InterpolateColumnDescription>;
+
+/// Outputs user-readable description into `out`.
+void dumpInterpolateDescription(const InterpolateDescription & description, const Block & header, WriteBuffer & out);
+
+std::string dumpInterpolateDescription(const InterpolateDescription & description);
+
+JSONBuilder::ItemPtr explainInterpolateDescription(const InterpolateDescription & description, const Block & header);
+
+}