From bf69755adab474fbd166209ab7675537d1a9aeeb Mon Sep 17 00:00:00 2001
From: Manas Alekar <manas@clickhouse.com>
Date: Tue, 13 Jun 2023 01:18:36 -0700
Subject: [PATCH] Address some usability issues with INTO OUTFILE usage.

---
 src/Client/ClientBase.cpp             | 20 ++++++++++++++++++++
 src/Parsers/ASTQueryWithOutput.cpp    |  2 ++
 src/Parsers/ASTQueryWithOutput.h      |  1 +
 src/Parsers/ParserQueryWithOutput.cpp |  6 ++++++
 4 files changed, 29 insertions(+)

diff --git a/src/Client/ClientBase.cpp b/src/Client/ClientBase.cpp
index 6f295c11070..fc108b8f57d 100644
--- a/src/Client/ClientBase.cpp
+++ b/src/Client/ClientBase.cpp
@@ -568,6 +568,13 @@ try
                 CompressionMethod compression_method = chooseCompressionMethod(out_file, compression_method_string);
                 UInt64 compression_level = 3;
 
+                if (query_with_output->is_outfile_append && query_with_output->is_outfile_truncate)
+                {
+                    throw Exception(
+                        ErrorCodes::BAD_ARGUMENTS,
+                        "Cannot use INTO OUTFILE with APPEND and TRUNCATE simultaneously.");
+                }
+
                 if (query_with_output->is_outfile_append && compression_method != CompressionMethod::None)
                 {
                     throw Exception(
@@ -589,9 +596,22 @@ try
                             range.second);
                 }
 
+                std::error_code ec;
+                if (std::filesystem::is_regular_file(out_file, ec))
+                {
+                    if (!query_with_output->is_outfile_append && !query_with_output->is_outfile_truncate)
+                    {
+                        throw Exception(
+                            ErrorCodes::CANNOT_OPEN_FILE,
+                            "File {} exists, consider using 'INTO OUTFILE ... APPEND' or 'INTO OUTFILE ... TRUNCATE' if appropriate.",
+                            out_file);
+                    }
+                }
                 auto flags = O_WRONLY | O_EXCL;
                 if (query_with_output->is_outfile_append)
                     flags |= O_APPEND;
+                else if (query_with_output->is_outfile_truncate)
+                    flags |= O_TRUNC;
                 else
                     flags |= O_CREAT;
 
diff --git a/src/Parsers/ASTQueryWithOutput.cpp b/src/Parsers/ASTQueryWithOutput.cpp
index 5f717715a69..4bf1e6cb231 100644
--- a/src/Parsers/ASTQueryWithOutput.cpp
+++ b/src/Parsers/ASTQueryWithOutput.cpp
@@ -39,6 +39,8 @@ void ASTQueryWithOutput::formatImpl(const FormatSettings & s, FormatState & stat
         s.ostr << (s.hilite ? hilite_keyword : "");
         if (is_outfile_append)
             s.ostr << " APPEND";
+        if (is_outfile_truncate)
+            s.ostr << " TRUNCATE";
         if (is_into_outfile_with_stdout)
             s.ostr << " AND STDOUT";
         s.ostr << (s.hilite ? hilite_none : "");
diff --git a/src/Parsers/ASTQueryWithOutput.h b/src/Parsers/ASTQueryWithOutput.h
index 7db021405e7..6f9cafc89a9 100644
--- a/src/Parsers/ASTQueryWithOutput.h
+++ b/src/Parsers/ASTQueryWithOutput.h
@@ -17,6 +17,7 @@ public:
     ASTPtr out_file;
     bool is_into_outfile_with_stdout = false;
     bool is_outfile_append = false;
+    bool is_outfile_truncate = false;
     ASTPtr format;
     ASTPtr settings_ast;
     ASTPtr compression;
diff --git a/src/Parsers/ParserQueryWithOutput.cpp b/src/Parsers/ParserQueryWithOutput.cpp
index 6796f4528c4..2bfe7353be4 100644
--- a/src/Parsers/ParserQueryWithOutput.cpp
+++ b/src/Parsers/ParserQueryWithOutput.cpp
@@ -109,6 +109,12 @@ bool ParserQueryWithOutput::parseImpl(Pos & pos, ASTPtr & node, Expected & expec
             query_with_output.is_outfile_append = true;
         }
 
+        ParserKeyword s_truncate("TRUNCATE");
+        if (s_truncate.ignore(pos, expected))
+        {
+            query_with_output.is_outfile_truncate = true;
+        }
+
         ParserKeyword s_stdout("AND STDOUT");
         if (s_stdout.ignore(pos, expected))
         {