Some fixups

docs/en/sql-reference/functions/string-functions.md

@@ -429,7 +429,7 @@ SELECT format('{} {}', 'Hello', 'World')
 
 ## concat
 
-Concatenates the strings listed in the arguments without separator.
+Concatenates the given arguments.
 
 **Syntax**
 
@@ -439,7 +439,9 @@ concat(s1, s2, ...)
 
 **Arguments**
 
-Values of arbitrary types. If an argument is not a String or FixedString, it is converted to the String type using the default serialization.
+At least two values of arbitrary type.
+
+Arguments which are not of types [String](../../sql-reference/data-types/string.md) or [FixedString](../../sql-reference/data-types/fixedstring.md) are converted to strings using their default serialization. As this decreases performance, it is not recommended to use non-String/FixedString arguments.
 
 **Returned values**
 
@@ -449,6 +451,8 @@ If any of arguments is `NULL`, the function returns `NULL`.
 
 **Example**
 
+Query:
+
 ``` sql
 SELECT concat('Hello, ', 'World!');
 ```
@@ -461,7 +465,7 @@ Result:
 └─────────────────────────────┘
 ```
 
-**Example**
+Query:
 
 ```sql
 SELECT concat(42, 144);
@@ -540,6 +544,8 @@ Concatenates the given strings with a given separator.
 concatWithSeparator(sep, expr1, expr2, expr3...)
 ```
 
+Alias: `concat_ws`
+
 **Arguments**
 
 - sep — separator. Const [String](../../sql-reference/data-types/string.md) or [FixedString](../../sql-reference/data-types/fixedstring.md).

src/Columns/ColumnStringHelpers.h

@@ -62,7 +62,7 @@ public:
         return buffer;
     }
 
-    inline void rowWritten()
+    void rowWritten()
     {
         if constexpr (std::is_same_v<ColumnType, ColumnFixedString>)
         {

src/Functions/concat.cpp

@@ -91,7 +91,6 @@ private:
         else
         {
             /// Fallback: use generic implementation for not very important cases.
-            /// Concat of arbitrary types also goes here.
             return executeFormatImpl(arguments, input_rows_count);
         }
 
@@ -108,7 +107,7 @@ private:
         std::vector<const ColumnString::Offsets *> offsets(num_arguments);
         std::vector<size_t> fixed_string_sizes(num_arguments);
         std::vector<std::optional<String>> constant_strings(num_arguments);
-        std::vector<ColumnPtr> converted_col_ptrs(num_arguments);
+        std::vector<ColumnString::MutablePtr> converted_col_ptrs(num_arguments);
         bool has_column_string = false;
         bool has_column_fixed_string = false;
         for (size_t i = 0; i < num_arguments; ++i)
@@ -132,14 +131,13 @@ private:
             }
             else
             {
-                // An arbitrary type argument: converting it to a StringColumn first
+                /// A non-String/non-FixedString-type argument: use the default serialization to convert it to String
                 const auto full_column = column->convertToFullIfNeeded();
                 const auto serialization = arguments[i].type->getDefaultSerialization();
-                ColumnString::MutablePtr converted_col_str = ColumnString::create();
+                auto converted_col_str = ColumnString::create();
-                static FormatSettings format_settings;
-
                 ColumnStringHelpers::WriteHelper write_helper(*converted_col_str, column->size());
                 auto & write_buffer = write_helper.getWriteBuffer();
+                FormatSettings format_settings;
                 for (size_t j = 0; j < column->size(); ++j)
                 {
                     serialization->serializeText(*full_column, j, write_buffer, format_settings);
@@ -147,12 +145,12 @@ private:
                 }
                 write_helper.finalize();
 
-                // Same as the normal `ColumnString` branch
+                /// Same as the normal `ColumnString` branch
                 has_column_string = true;
                 data[i] = &converted_col_str->getChars();
                 offsets[i] = &converted_col_str->getOffsets();
 
-                // keep the refcounted-pointer around (to be able to use data/offsets later)
+                /// Keep the refcounted-pointer alive
                 converted_col_ptrs[i] = std::move(converted_col_str);
             }
         }

src/Functions/formatString.h

@@ -1,14 +1,14 @@
 #pragma once
 
+#include <Columns/ColumnString.h>
+#include <Common/format.h>
+#include <Common/memcpySmall.h>
+#include <base/types.h>
+
 #include <algorithm>
 #include <optional>
 #include <string>
 #include <vector>
-#include <Columns/ColumnString.h>
-#include <base/types.h>
-#include <Common/format.h>
-#include <Common/memcpySmall.h>
-
 
 namespace DB
 {

tests/queries/0_stateless/02775_show_columns_called_from_clickhouse.sql

@@ -5,7 +5,7 @@
 -- Tests the output of SHOW COLUMNS when called through the ClickHouse protocol.
 
 -- -----------------------------------------------------------------------------------
--- Please keep this test in-sync with 02775_show_columns_called_from_mysql.expect
+-- Please keep this test in-sync with 02775_show_columns_called_from_clickhouse.expect
 -- -----------------------------------------------------------------------------------
 
 DROP TABLE IF EXISTS tab;

tests/queries/0_stateless/02775_show_columns_called_from_mysql.expect

@@ -6,7 +6,7 @@
 # Tests the output of SHOW COLUMNS when called through the MySQL protocol.
 
 # -----------------------------------------------------------------------------------
-# Please keep this test in-sync with 02775_show_columns_called_through_clickhouse.sql
+# Please keep this test in-sync with 02775_show_columns_called_from_clickhouse.sql
 # -----------------------------------------------------------------------------------
 
 set basedir [file dirname $argv0]