From 3c045e1545798ddc662f50c526a0732649d73699 Mon Sep 17 00:00:00 2001
From: Vitaliy Lyudvichenko <vludv@yandex-team.ru>
Date: Wed, 28 Sep 2016 16:11:03 +0300
Subject: [PATCH] Added ability to skip plain JSON arrays. [#METR-22801]

---
 dbms/include/DB/IO/ReadHelpers.h |  2 +-
 dbms/src/IO/ReadHelpers.cpp      | 34 ++++++++++++++++++++++++++++++--
 2 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/dbms/include/DB/IO/ReadHelpers.h b/dbms/include/DB/IO/ReadHelpers.h
index 65d6b0bd1bd..d9bbcc9525d 100644
--- a/dbms/include/DB/IO/ReadHelpers.h
+++ b/dbms/include/DB/IO/ReadHelpers.h
@@ -810,7 +810,7 @@ inline void skipWhitespaceIfAny(ReadBuffer & buf)
 		++buf.position();
 }
 
-/// Skip json value (except array and object).
+/// Skips json value. If the value contains objects (i.e. {...} sequence), an exception will be thrown.
 void skipJSONFieldPlain(ReadBuffer & buf, const String & name_of_filed = "");
 
 
diff --git a/dbms/src/IO/ReadHelpers.cpp b/dbms/src/IO/ReadHelpers.cpp
index b5a93653ef6..5c7f7020eb4 100644
--- a/dbms/src/IO/ReadHelpers.cpp
+++ b/dbms/src/IO/ReadHelpers.cpp
@@ -595,11 +595,41 @@ void skipJSONFieldPlain(ReadBuffer & buf, const String & name_of_filed)
 	{
 		assertString("true", buf);
 	}
-	else if (*buf.position() == 'f')/// skip false
+	else if (*buf.position() == 'f') /// skip false
 	{
 		assertString("false", buf);
 	}
-	else if (*buf.position() == '{' || *buf.position() == '[') /// fail on nested objects
+	else if (*buf.position() == '[')
+	{
+		++buf.position();
+		skipWhitespaceIfAny(buf);
+
+		if (!buf.eof() && *buf.position() == ']') /// skip empty array
+		{
+			++buf.position();
+			return;
+		}
+
+		while (true)
+		{
+			skipJSONFieldPlain(buf, name_of_filed);
+			skipWhitespaceIfAny(buf);
+
+			if (!buf.eof() && *buf.position() == ',')
+			{
+				++buf.position();
+				skipWhitespaceIfAny(buf);
+			}
+			else if (!buf.eof() && *buf.position() == ']')
+			{
+				++buf.position();
+				break;
+			}
+			else
+				throw Exception("Unexpected symbol for key '" + name_of_filed + "'", ErrorCodes::INCORRECT_DATA);
+		}
+	}
+	else if (*buf.position() == '{') /// fail on objects
 	{
 		throw Exception("Unexpected nested field for key '" + name_of_filed + "'", ErrorCodes::INCORRECT_DATA);
 	}