Changing Grammar to extend CASE WHEN statement:
- allow multiple WHEN statements - allow for syntax like `CASE x WHEN 1 THEN 2 WHEN 3 THEN 4 ELSE 5 END` NOTE: This changes also the way the CASE operator is stored: - CASE [expr] exprList [ELSE expr2] END - exprList holds each of the WHEN statements with: expr := WHEN, expr2 := THEN Added also tests in test/select_tests.cpp and adapted the existing one to reflect the new storage
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@ -195,7 +195,7 @@ int yyerror(YYLTYPE* llocp, SQLParserResult* result, yyscan_t scanner, const cha
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%type <expr> expr operand scalar_expr unary_expr binary_expr logic_expr exists_expr
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%type <expr> function_expr between_expr expr_alias param_expr
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%type <expr> column_name literal int_literal num_literal string_literal
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%type <expr> comp_expr opt_where join_condition opt_having case_expr in_expr hint
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%type <expr> comp_expr opt_where join_condition opt_having case_expr case_list in_expr hint
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%type <expr> array_expr array_index null_literal
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%type <limit> opt_limit opt_top
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%type <order> order_desc
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@ -781,11 +781,18 @@ in_expr:
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| operand NOT IN '(' select_no_paren ')' { $$ = Expr::makeOpUnary(kOpNot, Expr::makeInOperator($1, $5)); }
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;
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// TODO: allow no else specified
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// CASE grammar based on: flex & bison by John Levine
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// https://www.safaribooksonline.com/library/view/flex-bison/9780596805418/ch04.html#id352665
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case_expr:
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CASE WHEN expr THEN operand END { $$ = Expr::makeCase($3, $5); }
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CASE WHEN expr THEN operand ELSE operand END { $$ = Expr::makeCase($3, $5, $7); }
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CASE expr case_list END { $$ = Expr::makeCaseExpr($2, $3); }
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| CASE expr case_list ELSE expr END { $$ = Expr::makeCaseExpr($2, $3, $5); }
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| CASE case_list END { $$ = Expr::makeCase($2); }
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| CASE case_list ELSE expr END { $$ = Expr::makeCase($2, $4); }
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;
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case_list:
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WHEN expr THEN expr { $$ = Expr::makeCaseCondition($2, $4); }
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| case_list WHEN expr THEN expr { $$ = Expr::joinCaseCondition($1, Expr::makeCaseCondition($3, $5)); }
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;
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exists_expr:
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@ -68,22 +68,53 @@ namespace hsql {
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return e;
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}
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Expr* Expr::makeCase(Expr* expr, Expr* then) {
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Expr* e = new Expr(kExprOperator);
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Expr* Expr::makeCaseCondition(Expr* expr, Expr* then) {
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Expr* e = new Expr(kExprWhenCondition);
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e->expr = expr;
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e->opType = kOpCase;
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e->exprList = new std::vector<Expr*>();
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e->exprList->push_back(then);
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e->expr2 = then;
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return e;
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}
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Expr* Expr::makeCase(Expr* expr, Expr* then, Expr* other) {
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Expr* Expr::joinCaseCondition(Expr* expr1, Expr* expr2) {
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Expr* e = new Expr(kExprOperator);
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e->opType = kOpPlus;
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if (expr1->exprList != nullptr) {
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e->exprList = expr1->exprList;
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} else {
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e->exprList = new std::vector<Expr*>();
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e->exprList->push_back(expr1);
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}
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e->exprList->push_back(expr2);
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return e;
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}
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Expr* Expr::makeCase(Expr* when) {
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Expr* e = new Expr(kExprOperator);
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e->expr = expr;
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e->opType = kOpCase;
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e->exprList = new std::vector<Expr*>();
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e->exprList->push_back(then);
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e->exprList->push_back(other);
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if (when->exprList != nullptr) {
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e->exprList = when->exprList;
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} else {
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e->exprList = new std::vector<Expr*>();
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e->exprList->push_back(when);
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}
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return e;
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}
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Expr* Expr::makeCase(Expr* when, Expr* other) {
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Expr* e = Expr::makeCase(when);
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e->expr2 = other;
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return e;
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}
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Expr* Expr::makeCaseExpr(Expr* expr, Expr* when) {
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Expr* e = Expr::makeCase(when);
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e->expr = expr;
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return e;
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}
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Expr* Expr::makeCaseExpr(Expr* expr, Expr* when, Expr* other) {
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Expr* e = Expr::makeCase(when, other);
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e->expr = expr;
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return e;
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}
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@ -25,7 +25,8 @@ namespace hsql {
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kExprSelect,
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kExprHint,
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kExprArray,
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kExprArrayIndex
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kExprArrayIndex,
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kExprWhenCondition
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};
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// Operator types. These are important for expressions of type kExprOperator.
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@ -113,9 +114,17 @@ namespace hsql {
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static Expr* makeBetween(Expr* expr, Expr* left, Expr* right);
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static Expr* makeCase(Expr* expr, Expr* then);
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static Expr* makeCaseCondition(Expr* expr, Expr* then);
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static Expr* makeCase(Expr* expr, Expr* then, Expr* other);
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static Expr* joinCaseCondition(Expr* expr, Expr* then);
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static Expr* makeCase(Expr* when);
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static Expr* makeCase(Expr* when, Expr* other);
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static Expr* makeCaseExpr(Expr* expr, Expr* when);
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static Expr* makeCaseExpr(Expr* expr, Expr* when, Expr* other);
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static Expr* makeLiteral(int64_t val);
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@ -214,9 +214,74 @@ TEST(SelectCaseWhen) {
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ASSERT_NOTNULL(caseExpr);
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ASSERT(caseExpr->isType(kExprOperator));
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ASSERT_EQ(caseExpr->opType, kOpCase);
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ASSERT(caseExpr->expr->isType(kExprOperator));
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ASSERT_EQ(caseExpr->expr->opType, kOpEquals);
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ASSERT_NULL(caseExpr->expr);
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ASSERT_NOTNULL(caseExpr->exprList);
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ASSERT_NOTNULL(caseExpr->expr2);
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ASSERT_EQ(caseExpr->exprList->size(), 1);
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ASSERT(caseExpr->expr2->isType(kExprLiteralInt));
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Expr* whenExpr = caseExpr->exprList->at(0);
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ASSERT(whenExpr->expr->isType(kExprOperator));
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ASSERT_EQ(whenExpr->expr->opType, kOpEquals);
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ASSERT(whenExpr->expr->expr->isType(kExprColumnRef));
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ASSERT(whenExpr->expr->expr2->isType(kExprLiteralString));
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}
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TEST(SelectCaseWhenWhen) {
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TEST_PARSE_SINGLE_SQL(
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"SELECT CASE WHEN x = 1 THEN 1 WHEN 1.25 < x THEN 2 END FROM test;",
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kStmtSelect,
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SelectStatement,
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result,
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stmt);
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ASSERT_EQ(stmt->selectList->size(), 1);
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Expr* caseExpr = stmt->selectList->at(0);
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ASSERT_NOTNULL(caseExpr);
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ASSERT(caseExpr->isType(kExprOperator));
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ASSERT_EQ(caseExpr->opType, kOpCase);
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// CASE [expr] [exprList] [expr2]
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// [expr] [expr]
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// [expr] [expr2] [expr] [expr2]
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// CASE (null) WHEN X = 1 THEN 1 WHEN 1.25 < x THEN 2 (null)
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ASSERT_NULL(caseExpr->expr);
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ASSERT_NOTNULL(caseExpr->exprList);
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ASSERT_NULL(caseExpr->expr2);
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ASSERT_EQ(caseExpr->exprList->size(), 2);
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Expr* whenExpr = caseExpr->exprList->at(0);
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ASSERT_EQ(whenExpr->expr->opType, kOpEquals);
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ASSERT(whenExpr->expr->expr->isType(kExprColumnRef));
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ASSERT(whenExpr->expr->expr2->isType(kExprLiteralInt));
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Expr* whenExpr2 = caseExpr->exprList->at(1);
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ASSERT_EQ(whenExpr2->expr->opType, kOpLess);
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ASSERT(whenExpr2->expr->expr->isType(kExprLiteralFloat));
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ASSERT(whenExpr2->expr->expr2->isType(kExprColumnRef));
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}
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TEST(SelectCaseValueWhenWhenElse) {
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TEST_PARSE_SINGLE_SQL(
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"SELECT CASE x WHEN 1 THEN 0 WHEN 2 THEN 3 WHEN 8 THEN 7 ELSE 4 END FROM test;",
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kStmtSelect,
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SelectStatement,
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result,
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stmt);
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ASSERT_EQ(stmt->selectList->size(), 1);
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Expr* caseExpr = stmt->selectList->at(0);
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ASSERT_NOTNULL(caseExpr);
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ASSERT(caseExpr->isType(kExprOperator));
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ASSERT_EQ(caseExpr->opType, kOpCase);
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ASSERT_NOTNULL(caseExpr->expr);
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ASSERT_NOTNULL(caseExpr->exprList);
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ASSERT_NOTNULL(caseExpr->expr2);
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ASSERT_EQ(caseExpr->exprList->size(), 3);
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ASSERT(caseExpr->expr->isType(kExprColumnRef));
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Expr* whenExpr = caseExpr->exprList->at(2);
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ASSERT(whenExpr->expr->isType(kExprLiteralInt));
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ASSERT_EQ(whenExpr->expr2->ival, 7);
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}
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TEST(SelectJoin) {
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