implement EXISTS conditional

src/parser/bison_parser.y

@@ -195,7 +195,8 @@ int yyerror(YYLTYPE* llocp, SQLParserResult** result, yyscan_t scanner, const ch
 %type <uval>		import_file_type opt_join_type column_type
 %type <table> 		from_clause table_ref table_ref_atomic table_ref_name
 %type <table>		join_clause join_table table_ref_name_no_alias
-%type <expr> 		expr operand scalar_expr unary_expr binary_expr logic_expr function_expr between_expr star_expr expr_alias placeholder_expr
+%type <expr> 		expr operand scalar_expr unary_expr binary_expr logic_expr exists_expr
+%type <expr>		function_expr between_expr star_expr expr_alias placeholder_expr
 %type <expr> 		column_name literal int_literal num_literal string_literal
 %type <expr> 		comp_expr opt_where join_condition opt_having
 %type <limit>		opt_limit opt_top
@@ -604,6 +605,7 @@ expr:
 		operand
 	|	between_expr
 	|	logic_expr
+	|	exists_expr
 	;
 
 operand:
@@ -643,6 +645,10 @@ logic_expr:
 	|	expr OR expr	{ $$ = Expr::makeOpBinary($1, Expr::OR, $3); }
 	;
 
+exists_expr:
+		EXISTS '(' select_no_paren ')' { $$ = Expr::makeExists($3); }
+	;
+
 comp_expr:
 		operand '=' operand			{ $$ = Expr::makeOpBinary($1, '=', $3); }
 	|	operand NOTEQUALS operand	{ $$ = Expr::makeOpBinary($1, Expr::NOT_EQUALS, $3); }

src/sql/Expr.cpp

@@ -50,6 +50,7 @@ namespace hsql {
   Expr* Expr::makeBetween(Expr* expr, Expr* left, Expr* right) {
     Expr* e = new Expr(kExprOperator);
     e->expr = expr;
+    e->opType = BETWEEN;
     e->exprList = new std::vector<Expr*>();
     e->exprList->push_back(left);
     e->exprList->push_back(right);
@@ -108,6 +109,13 @@ namespace hsql {
     return e;
   }
 
+  Expr* Expr::makeExists(SelectStatement* select) {
+    Expr* e = new Expr(kExprOperator);
+    e->opType = EXISTS;
+    e->select = select;
+    return e;
+  }
+
   bool Expr::isType(ExprType e_type) {
     return e_type == type;
   }

src/sql/Expr.h

@@ -34,6 +34,8 @@ namespace hsql {
     // + - * / < > = %
     // Non-trivial are: <> <= >= LIKE ISNULL NOT
     enum OperatorType {
+      NONE,
+
       // Ternary operators
       BETWEEN,
 
@@ -50,7 +52,8 @@ namespace hsql {
       // Unary operators.
       NOT,
       UMINUS,
-      ISNULL
+      ISNULL,
+      EXISTS
     };
 
 
@@ -123,6 +126,8 @@ namespace hsql {
     static Expr* makePlaceholder(int id);
 
     static Expr* makeSelect(SelectStatement* select);
+
+    static Expr* makeExists(SelectStatement* select);
   };
 
 // Zero initializes an Expr object and assigns it to a space in the heap

test/select_tests.cpp

@@ -160,7 +160,7 @@ TEST(SelectBetweenTest) {
 
 TEST(SelectConditionalSelectTest) {
   TEST_PARSE_SINGLE_SQL(
-    "SELECT * FROM t WHERE a = (SELECT MIN(v) FROM tt);",
+    "SELECT * FROM t WHERE a = (SELECT MIN(v) FROM tt) AND EXISTS (SELECT * FROM test WHERE x < a);",
     kStmtSelect,
     SelectStatement,
     result,
@@ -169,18 +169,31 @@ TEST(SelectConditionalSelectTest) {
   Expr* where = stmt->whereClause;
   ASSERT_NOTNULL(where);
   ASSERT(where->isType(kExprOperator));
-  ASSERT(where->isSimpleOp('='));
+  ASSERT_EQ(where->opType, Expr::AND);
 
-  ASSERT_NOTNULL(where->expr);
-  ASSERT_STREQ(where->expr->getName(), "a");
-  ASSERT(where->expr->isType(kExprColumnRef));
+  // a = (SELECT ...)
+  Expr* cond1 = where->expr;
+  ASSERT_NOTNULL(cond1);
+  ASSERT_NOTNULL(cond1->expr);
+  ASSERT(cond1->isSimpleOp('='));
+  ASSERT_STREQ(cond1->expr->getName(), "a");
+  ASSERT(cond1->expr->isType(kExprColumnRef));
 
-  ASSERT_NOTNULL(where->expr2);
-  ASSERT(where->expr2->isType(kExprSelect));
+  ASSERT_NOTNULL(cond1->expr2);
+  ASSERT(cond1->expr2->isType(kExprSelect));
 
-  SelectStatement* select2 = where->expr2->select;
+  SelectStatement* select2 = cond1->expr2->select;
   ASSERT_NOTNULL(select2);
   ASSERT_STREQ(select2->fromTable->getName(), "tt")
 
+
+  // EXISTS (SELECT ...)
+  Expr* cond2 = where->expr2;
+  ASSERT_EQ(cond2->opType, Expr::EXISTS);
+  ASSERT_NOTNULL(cond2->select);
+
+  SelectStatement* ex_select = cond2->select;
+  ASSERT_STREQ(ex_select->fromTable->getName(), "test")
+
   delete result;
 }