implement CASE WHEN expressions

src/parser/bison_parser.y

@@ -169,12 +169,11 @@ int yyerror(YYLTYPE* llocp, SQLParserResult** result, yyscan_t scanner, const ch
 %token INSERT ISNULL OFFSET RENAME SCHEMA SELECT SORTED
 %token TABLES UNIQUE UNLOAD UPDATE VALUES AFTER ALTER CROSS
 %token DELTA GROUP INDEX INNER LIMIT LOCAL MERGE MINUS ORDER
-%token OUTER RIGHT TABLE UNION USING WHERE CALL DATE DESC
-%token DROP FILE FROM FULL HASH HINT INTO JOIN LEFT LIKE
-%token LOAD NULL PART PLAN SHOW TEXT TIME VIEW WITH ADD ALL
-%token AND ASC CSV FOR INT KEY NOT OFF SET TBL TOP AS BY IF
-%token IN IS OF ON OR TO
-
+%token OUTER RIGHT TABLE UNION USING WHERE CALL CASE DATE
+%token DESC DROP ELSE FILE FROM FULL HASH HINT INTO JOIN
+%token LEFT LIKE LOAD NULL PART PLAN SHOW TEXT THEN TIME
+%token VIEW WHEN WITH ADD ALL AND ASC CSV END FOR INT KEY
+%token NOT OFF SET TBL TOP AS BY IF IN IS OF ON OR TO
 
 /*********************************
  ** Non-Terminal types (http://www.gnu.org/software/bison/manual/html_node/Type-Decl.html)
@@ -198,7 +197,7 @@ int yyerror(YYLTYPE* llocp, SQLParserResult** result, yyscan_t scanner, const ch
 %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 <expr> 		comp_expr opt_where join_condition opt_having case_expr
 %type <limit>		opt_limit opt_top
 %type <order>		order_desc
 %type <order_type>	opt_order_type
@@ -606,6 +605,7 @@ expr:
 	|	between_expr
 	|	logic_expr
 	|	exists_expr
+	|	case_expr
 	;
 
 operand:
@@ -645,6 +645,11 @@ logic_expr:
 	|	expr OR expr	{ $$ = Expr::makeOpBinary($1, Expr::OR, $3); }
 	;
 
+// TODO: allow no else specified
+case_expr:
+		CASE WHEN operand THEN operand ELSE operand END { $$ = Expr::makeCase($3, $5, $7); }
+	;
+
 exists_expr:
 		EXISTS '(' select_no_paren ')' { $$ = Expr::makeExists($3); }
 	;

src/parser/flex_lexer.l

@@ -54,11 +54,8 @@
 <COMMENT>[^\n]*	/* skipping comment content until a end of line is read */;
 <COMMENT>\n 	BEGIN(INITIAL);
 
-
 [ \t\n]+	/* skip whitespace */;
 
-
-
 DEALLOCATE	TOKEN(DEALLOCATE)
 PARAMETERS	TOKEN(PARAMETERS)
 INTERSECT	TOKEN(INTERSECT)
@@ -127,9 +124,11 @@ UNION		TOKEN(UNION)
 USING		TOKEN(USING)
 WHERE		TOKEN(WHERE)
 CALL		TOKEN(CALL)
+CASE		TOKEN(CASE)
 DATE		TOKEN(DATE)
 DESC		TOKEN(DESC)
 DROP		TOKEN(DROP)
+ELSE		TOKEN(ELSE)
 FILE		TOKEN(FILE)
 FROM		TOKEN(FROM)
 FULL		TOKEN(FULL)
@@ -145,14 +144,17 @@ PART		TOKEN(PART)
 PLAN		TOKEN(PLAN)
 SHOW		TOKEN(SHOW)
 TEXT		TOKEN(TEXT)
+THEN		TOKEN(THEN)
 TIME		TOKEN(TIME)
 VIEW		TOKEN(VIEW)
+WHEN		TOKEN(WHEN)
 WITH		TOKEN(WITH)
 ADD			TOKEN(ADD)
 ALL			TOKEN(ALL)
 AND			TOKEN(AND)
 ASC			TOKEN(ASC)
 CSV			TOKEN(CSV)
+END			TOKEN(END)
 FOR			TOKEN(FOR)
 INT			TOKEN(INT)
 KEY			TOKEN(KEY)
@@ -171,15 +173,12 @@ ON			TOKEN(ON)
 OR			TOKEN(OR)
 TO			TOKEN(TO)
 
-
 "<>" 		TOKEN(NOTEQUALS)
 "<="		TOKEN(LESSEQ)
 ">="		TOKEN(GREATEREQ)
 
-
 [-+*/(){},.;<>=^%:?]	{ return yytext[0]; }
 
-
 [0-9]+"."[0-9]* |
 "."[0-9]*	{
 	yylval->fval = atof(yytext);
@@ -202,7 +201,6 @@ TO			TOKEN(TO)
 	return SQL_IDENTIFIER;
 }
 
-
 '[^'\n]*' {
 	// Crop the leading and trailing quote char
 	yylval->sval = hsql::substr(yytext, 1, strlen(yytext)-1);

src/parser/sql_keywords.txt

@@ -140,6 +140,11 @@ IS
 ISNULL
 BETWEEN
 ESCAPE
+CASE
+WHEN
+THEN
+ELSE
+END
 
 // With
 WITH

src/sql/Expr.cpp

@@ -57,6 +57,16 @@ namespace hsql {
     return e;
   }
 
+  Expr* Expr::makeCase(Expr* expr, Expr* then, Expr* other) {
+    Expr* e = new Expr(kExprOperator);
+    e->expr = expr;
+    e->opType = CASE;
+    e->exprList = new std::vector<Expr*>();
+    e->exprList->push_back(then);
+    e->exprList->push_back(other);
+    return e;
+  }
+
   Expr* Expr::makeLiteral(int64_t val) {
     Expr* e = new Expr(kExprLiteralInt);
     e->ival = val;

src/sql/Expr.h

@@ -38,6 +38,7 @@ namespace hsql {
 
       // Ternary operators
       BETWEEN,
+      CASE,
 
       // Binary operators.
       SIMPLE_OP,
@@ -111,6 +112,8 @@ namespace hsql {
 
     static Expr* makeBetween(Expr* expr, Expr* left, Expr* right);
 
+    static Expr* makeCase(Expr* expr, Expr* then, Expr* other);
+
     static Expr* makeLiteral(int64_t val);
 
     static Expr* makeLiteral(double val);

test/queries/tpc-h-08.sql

@@ -1,7 +1,7 @@
 -- http://www.sqlserver-dba.com/2011/09/this-is-a-followup-on-my-earlier-post-of-sql-server-test-data-generation-testing-tools-i-had-some-requests-for-my-set-up-pr.html
 SELECT O_YEAR, SUM(CASE WHEN NATION = 'BRAZIL' THEN VOLUME ELSE 0 END)/SUM(VOLUME) AS MKT_SHARE
 FROM (SELECT datepart(yy,O_ORDERDATE) AS O_YEAR, L_EXTENDEDPRICE*(1-L_DISCOUNT) AS VOLUME, N2.N_NAME AS NATION
- FROM PART, SUPPLIER, LINEITEM, ORDERS, CUSTOMER, NATION N1, NATION N2, REGION
+ FROM "PART", SUPPLIER, LINEITEM, ORDERS, CUSTOMER, NATION N1, NATION N2, REGION
  WHERE P_PARTKEY = L_PARTKEY AND S_SUPPKEY = L_SUPPKEY AND L_ORDERKEY = O_ORDERKEY
  AND O_CUSTKEY = C_CUSTKEY AND C_NATIONKEY = N1.N_NATIONKEY AND
  N1.N_REGIONKEY = R_REGIONKEY AND R_NAME = 'AMERICA' AND S_NATIONKEY = N2.N_NATIONKEY

test/select_tests.cpp

@@ -184,7 +184,7 @@ TEST(SelectConditionalSelectTest) {
 
   SelectStatement* select2 = cond1->expr2->select;
   ASSERT_NOTNULL(select2);
-  ASSERT_STREQ(select2->fromTable->getName(), "tt")
+  ASSERT_STREQ(select2->fromTable->getName(), "tt");
 
 
   // EXISTS (SELECT ...)
@@ -193,7 +193,33 @@ TEST(SelectConditionalSelectTest) {
   ASSERT_NOTNULL(cond2->select);
 
   SelectStatement* ex_select = cond2->select;
-  ASSERT_STREQ(ex_select->fromTable->getName(), "test")
+  ASSERT_STREQ(ex_select->fromTable->getName(), "test");
+
+  delete result;
+}
+
+TEST(SelectCaseWhen) {
+  TEST_PARSE_SINGLE_SQL(
+    "SELECT MAX(CASE WHEN a = 'foo' THEN x ELSE 0 END) FROM test;",
+    kStmtSelect,
+    SelectStatement,
+    result,
+    stmt);
+
+  ASSERT_EQ(stmt->selectList->size(), 1);
+  Expr* func = stmt->selectList->at(0);
+
+  ASSERT_NOTNULL(func);
+  ASSERT(func->isType(kExprFunctionRef));
+  ASSERT_EQ(func->exprList->size(), 1);
+
+  Expr* caseExpr = func->exprList->at(0);
+  ASSERT_NOTNULL(caseExpr);
+  ASSERT(caseExpr->isType(kExprOperator));
+  ASSERT_EQ(caseExpr->opType, Expr::CASE);
+  ASSERT(caseExpr->expr->isType(kExprOperator));
+  ASSERT(caseExpr->expr->isSimpleOp('='));
+  ASSERT_EQ(caseExpr->exprList->size(), 2);
 
   delete result;
 }