Allow to parse Date as YYYYMMDD

src/IO/ReadHelpers.cpp

@@ -768,17 +768,6 @@ ReturnType readDateTextFallback(LocalDate & date, ReadBuffer & buf)
         return ReturnType(false);
     };
 
-    auto ignore_delimiter = [&]
-    {
-        if (!buf.eof() && !isNumericASCII(*buf.position()))
-        {
-            ++buf.position();
-            return true;
-        }
-        else
-            return false;
-    };
-
     auto append_digit = [&](auto & x)
     {
         if (!buf.eof() && isNumericASCII(*buf.position()))
@@ -792,27 +781,44 @@ ReturnType readDateTextFallback(LocalDate & date, ReadBuffer & buf)
     };
 
     UInt16 year = 0;
+    UInt8 month = 0;
+    UInt8 day = 0;
+
     if (!append_digit(year)
         || !append_digit(year) // NOLINT
         || !append_digit(year) // NOLINT
         || !append_digit(year)) // NOLINT
         return error();
 
-    if (!ignore_delimiter())
+    if (buf.eof())
         return error();
 
-    UInt8 month = 0;
+    if (isNumericASCII(*buf.position()))
-    if (!append_digit(month))
+    {
-        return error();
+        /// YYYYMMDD
-    append_digit(month);
+        if (!append_digit(month)
+            || !append_digit(month) // NOLINT
+            || !append_digit(day)
+            || !append_digit(day)) // NOLINT
+            return error();
+    }
+    else
+    {
+        ++buf.position();
 
-    if (!ignore_delimiter())
+        if (!append_digit(month))
-        return error();
+            return error();
+        append_digit(month);
 
-    UInt8 day = 0;
+        if (!buf.eof() && !isNumericASCII(*buf.position()))
-    if (!append_digit(day))
+            ++buf.position();
-        return error();
+        else
-    append_digit(day);
+            return error();
+
+        if (!append_digit(day))
+            return error();
+        append_digit(day);
+    }
 
     date = LocalDate(year, month, day);
     return ReturnType(true);

src/IO/ReadHelpers.h

@@ -597,35 +597,45 @@ inline ReturnType readDateTextImpl(LocalDate & date, ReadBuffer & buf)
         /// YYYY-MM-D
         /// YYYY-M-DD
         /// YYYY-M-D
+        /// YYYYMMDD
 
         /// The delimiters can be arbitrary characters, like YYYY/MM!DD, but obviously not digits.
 
         UInt16 year = (pos[0] - '0') * 1000 + (pos[1] - '0') * 100 + (pos[2] - '0') * 10 + (pos[3] - '0');
+        UInt8 month;
+        UInt8 day;
         pos += 5;
 
         if (isNumericASCII(pos[-1]))
-            return ReturnType(false);
-
-        UInt8 month = pos[0] - '0';
-        if (isNumericASCII(pos[1]))
         {
-            month = month * 10 + pos[1] - '0';
+            /// YYYYMMDD
+            month = (pos[-1] - '0') * 10 + (pos[0] - '0');
+            day = (pos[1] - '0') * 10 + (pos[2] - '0');
             pos += 3;
         }
         else
-            pos += 2;
-
-        if (isNumericASCII(pos[-1]))
-            return ReturnType(false);
-
-        UInt8 day = pos[0] - '0';
-        if (isNumericASCII(pos[1]))
         {
-            day = day * 10 + pos[1] - '0';
+            month = pos[0] - '0';
-            pos += 2;
+            if (isNumericASCII(pos[1]))
+            {
+                month = month * 10 + pos[1] - '0';
+                pos += 3;
+            }
+            else
+                pos += 2;
+
+            if (isNumericASCII(pos[-1]))
+                return ReturnType(false);
+
+            day = pos[0] - '0';
+            if (isNumericASCII(pos[1]))
+            {
+                day = day * 10 + pos[1] - '0';
+                pos += 2;
+            }
+            else
+                pos += 1;
         }
-        else
-            pos += 1;
 
         buf.position() = pos;
         date = LocalDate(year, month, day);

tests/queries/0_stateless/02112_parse_date_yyyymmdd.reference

@@ -0,0 +1 @@
+2021-02-03	2021-03-04	2021-04-05

tests/queries/0_stateless/02112_parse_date_yyyymmdd.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+
+CURDIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+# shellcheck source=../shell_config.sh
+. "$CURDIR"/../shell_config.sh
+
+echo '20210203,2021-03-04,20210405' | $CLICKHOUSE_LOCAL --input-format CSV --structure 'a Date, b Date, c Date' --query 'SELECT * FROM table'