From 5abfcfcd4814bb4133a19749153668f614c0b9e1 Mon Sep 17 00:00:00 2001
From: Ivan Blinkov <github@blinkov.ru>
Date: Tue, 18 Dec 2018 17:40:30 +0300
Subject: [PATCH] Support proper syntax for dateDiff

---
 dbms/src/Parsers/ExpressionElementParsers.cpp | 65 +++++++++++++++++++
 dbms/src/Parsers/ExpressionElementParsers.h   |  6 ++
 .../00765_sql_compatibility_aliases.reference |  1 +
 .../00765_sql_compatibility_aliases.sql       |  1 +
 4 files changed, 73 insertions(+)

diff --git a/dbms/src/Parsers/ExpressionElementParsers.cpp b/dbms/src/Parsers/ExpressionElementParsers.cpp
index ebbeb6bceac..d189b178de9 100644
--- a/dbms/src/Parsers/ExpressionElementParsers.cpp
+++ b/dbms/src/Parsers/ExpressionElementParsers.cpp
@@ -698,6 +698,70 @@ bool ParserExtractExpression::parseImpl(Pos & pos, ASTPtr & node, Expected & exp
     return true;
 }
 
+bool ParserDateDiffExpression::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
+{
+    const char * interval_name = nullptr;
+    ASTPtr left_node;
+    ASTPtr right_node;
+
+    if (!(ParserKeyword("DATEDIFF").ignore(pos, expected) || ParserKeyword("DATE_DIFF").ignore(pos, expected)))
+        return false;
+
+    if (pos->type != TokenType::OpeningRoundBracket)
+        return false;
+    ++pos;
+
+
+    if (ParserKeyword("SECOND").ignore(pos, expected))
+        interval_name = "second";
+    else if (ParserKeyword("MINUTE").ignore(pos, expected))
+        interval_name = "minute";
+    else if (ParserKeyword("HOUR").ignore(pos, expected))
+        interval_name = "hour";
+    else if (ParserKeyword("DAY").ignore(pos, expected))
+        interval_name = "day";
+    else if (ParserKeyword("WEEK").ignore(pos, expected))
+        interval_name = "week";
+    else if (ParserKeyword("MONTH").ignore(pos, expected))
+        interval_name = "month";
+    else if (ParserKeyword("QUARTER").ignore(pos, expected))
+        interval_name = "quarter";
+    else if (ParserKeyword("YEAR").ignore(pos, expected))
+        interval_name = "year";
+    else
+        return false;
+
+    if (pos->type != TokenType::Comma)
+        return false;
+    ++pos;
+
+    if (!ParserExpression().parse(pos, left_node, expected))
+        return false;
+
+    if (pos->type != TokenType::Comma)
+        return false;
+    ++pos;
+
+    if (!ParserExpression().parse(pos, right_node, expected))
+        return false;
+
+    if (pos->type != TokenType::ClosingRoundBracket)
+        return false;
+    ++pos;
+
+    auto expr_list_args = std::make_shared<ASTExpressionList>();
+    expr_list_args->children = {std::make_shared<ASTLiteral>(interval_name), left_node, right_node};
+
+    auto func_node = std::make_shared<ASTFunction>();
+    func_node->name = "dateDiff";
+    func_node->arguments = std::move(expr_list_args);
+    func_node->children.push_back(func_node->arguments);
+
+    node = std::move(func_node);
+
+    return true;
+}
+
 
 bool ParserNull::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
 {
@@ -999,6 +1063,7 @@ bool ParserExpressionElement::parseImpl(Pos & pos, ASTPtr & node, Expected & exp
         || ParserLiteral().parse(pos, node, expected)
         || ParserCastExpression().parse(pos, node, expected)
         || ParserExtractExpression().parse(pos, node, expected)
+        || ParserDateDiffExpression().parse(pos, node, expected)
         || ParserSubstringExpression().parse(pos, node, expected)
         || ParserTrimExpression().parse(pos, node, expected)
         || ParserLeftExpression().parse(pos, node, expected)
diff --git a/dbms/src/Parsers/ExpressionElementParsers.h b/dbms/src/Parsers/ExpressionElementParsers.h
index 98aec4fa46c..c35a6613155 100644
--- a/dbms/src/Parsers/ExpressionElementParsers.h
+++ b/dbms/src/Parsers/ExpressionElementParsers.h
@@ -131,6 +131,12 @@ protected:
     bool parseImpl(Pos & pos, ASTPtr & node, Expected & expected) override;
 };
 
+class ParserDateDiffExpression : public IParserBase
+{
+protected:
+    const char * getName() const override { return "DATE_DIFF expression"; }
+    bool parseImpl(Pos & pos, ASTPtr & node, Expected & expected) override;
+};
 
 /** NULL literal.
   */
diff --git a/dbms/tests/queries/0_stateless/00765_sql_compatibility_aliases.reference b/dbms/tests/queries/0_stateless/00765_sql_compatibility_aliases.reference
index 297a6e93d4f..be273b59160 100644
--- a/dbms/tests/queries/0_stateless/00765_sql_compatibility_aliases.reference
+++ b/dbms/tests/queries/0_stateless/00765_sql_compatibility_aliases.reference
@@ -21,3 +21,4 @@ xxfoo
 fooabba
 fooabbafoo
 foo*
+-11
diff --git a/dbms/tests/queries/0_stateless/00765_sql_compatibility_aliases.sql b/dbms/tests/queries/0_stateless/00765_sql_compatibility_aliases.sql
index f54a0466558..79812497656 100644
--- a/dbms/tests/queries/0_stateless/00765_sql_compatibility_aliases.sql
+++ b/dbms/tests/queries/0_stateless/00765_sql_compatibility_aliases.sql
@@ -23,3 +23,4 @@ select trim(TRAILING 'x' FROM 'xxfooxx');
 select Trim(LEADING 'ab' FROM 'abbafooabba');
 select TRIM(both 'ab' FROM 'abbafooabbafooabba');
 select trim(LEADING '*[]{}|\\' FROM '\\|[[[}}}*foo*');
+select DATE_DIFF(MONTH, toDate('2018-12-18'), toDate('2018-01-01'));