SQL compatibility: provide POSITION(needle IN haystack) syntax.

src/Parsers/ExpressionElementParsers.cpp

@@ -343,6 +343,22 @@ bool ParserFunction::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
         throw Exception("Argument of function toDate is unquoted: toDate(" + contents_str + "), must be: toDate('" + contents_str + "')"
             , ErrorCodes::SYNTAX_ERROR);
     }
+    else if (Poco::toLower(getIdentifierName(identifier)) == "position")
+    {
+        /// POSITION(needle IN haystack) is equivalent to function position(haystack, needle)
+        const auto & list = expr_list_args->as<ASTExpressionList &>();
+        if (list.children.size() == 1)
+        {
+            const auto & in_func = list.children[0]->as<ASTFunction &>();
+            if (in_func.name == "in")
+            {
+                // switch the two arguments
+                const auto & arg_list = in_func.arguments->as<ASTExpressionList &>();
+                expr_list_args->children = {arg_list.children[1], arg_list.children[0]};
+            }
+
+        }
+    }
 
     /// The parametric aggregate function has two lists (parameters and arguments) in parentheses. Example: quantile(0.9)(x).
     if (allow_function_parameters && pos->type == TokenType::OpeningRoundBracket)

tests/queries/0_stateless/00233_position_function_family.reference

@@ -23796,3 +23796,16 @@
 1
 1
 1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1

tests/queries/0_stateless/00233_position_function_family.sql

@@ -13,6 +13,14 @@ select 1 = position('a', '', 1);
 select 2 = position('a', '', 2);
 select 0 = position('a', '', 3);
 
+select 1 = position('' in '');
+select 1 = position('' in 'abc');
+select 0 = position('abc' in '');
+select 1 = position('abc' in 'abc');
+select 2 = position('bc' in 'abc');
+select 3 = position('c' in 'abc');
+select 6 = position('/' IN s) FROM (SELECT 'Hello/World' AS s);
+
 select [1, 1, 2, 3, 4, 5, 0, 0, 0, 0] = groupArray(position('aaaa', '', number)) from numbers(10);
 select [1, 1, 2, 3, 4, 5, 0, 0, 0, 0] = groupArray(position(materialize('aaaa'), '', number)) from numbers(10);
 select [1, 1, 2, 3, 4, 5, 0, 0, 0, 0] = groupArray(position('aaaa', materialize(''), number)) from numbers(10);
@@ -54,6 +62,13 @@ select 0 = position('abcabc', 'b', 6);
 select 2 = position('abcabc', 'bca', 0);
 select 0 = position('abcabc', 'bca', 3);
 
+select 1 = position('' in '');
+select 1 = position('' in 'абв');
+select 0 = position('абв' in '');
+select 1 = position('абв' in 'абв');
+select 3 = position('бв' in 'абв');
+select 5 = position('в' in 'абв');
+
 select 1 = position(materialize(''), '');
 select 1 = position(materialize('абв'), '');
 select 0 = position(materialize(''), 'абв');