SQLParser: Introduce LIMIT clause

src/parser/sql/SQLGrammar.g4

@@ -38,6 +38,7 @@ select:
     whereClause?
     groupByClause?
     orderByClause?
+    limitClause?
     ;
 
 subquery:
@@ -78,6 +79,9 @@ orderByClause:
     SQL_ORDER SQL_BY selectIdent orderInformation
     (',' selectIdent orderInformation)*;
 
+limitClause:
+    SQL_LIMIT limit=INT_LITERAL;
+
 orderInformation:
     (asc=SQL_ASC|desc=SQL_DESC)?;
 
@@ -139,6 +143,7 @@ SQL_ASC: A S C;
 SQL_DESC: D E S C;
 SQL_AND: A N D;
 SQL_OR: O R;
+SQL_LIMIT: L I M I T;
 
 fragment A: [aA];
 fragment B: [bB];

src/parser/sql/SQLVisitor.cpp

@@ -18,6 +18,7 @@
 #include <ir/daphneir/Daphne.h>
 #include <parser/sql/SQLVisitor.h>
 #include "antlr4-runtime.h"
+#include "mlir/IR/BuiltinTypes.h"
 #include "mlir/IR/OpDefinition.h"
 
 #include <stdexcept>
@@ -504,6 +505,10 @@ antlrcpp::Any SQLVisitor::visitSelect(
             throw std::runtime_error(err_msg.str());
         }
     }
+    if(ctx->limitClause()) {
+        currentFrame = res;
+        res = utils.valueOrError(visit(ctx->limitClause()));
+    }
     return res;
 }
 
@@ -826,6 +831,26 @@ antlrcpp::Any SQLVisitor::visitOrderByClause(
     );
 }
 
+antlrcpp::Any SQLVisitor::visitLimitClause(
+    SQLGrammarParser::LimitClauseContext *ctx
+)
+{
+    mlir::Location loc = utils.getLoc(ctx->start);
+
+    mlir::Value start = builder.create<mlir::daphne::ConstantOp>(
+        loc, utils.sizeType, builder.getIndexAttr(0)
+    );
+
+    mlir::Value end = builder.create<mlir::daphne::ConstantOp>(
+        loc, utils.sizeType, builder.getIndexAttr(stoi(ctx->limit->getText()))
+    );
+
+    mlir::daphne::FrameType resType = currentFrame.getType().dyn_cast<mlir::daphne::FrameType>().withSameColumnTypes();
+    return static_cast<mlir::Value>(
+        builder.create<mlir::daphne::SliceRowOp>(loc, resType, currentFrame, start, end)
+    ); 
+}
+
 antlrcpp::Any SQLVisitor::visitOrderInformation(
     SQLGrammarParser::OrderInformationContext * ctx
 )

src/parser/sql/SQLVisitor.h

@@ -203,6 +203,9 @@ class SQLVisitor : public SQLGrammarVisitor {
 //orderByClause
     antlrcpp::Any visitOrderByClause(SQLGrammarParser::OrderByClauseContext * ctx) override;
 
+//limitClause
+    antlrcpp::Any visitLimitClause(SQLGrammarParser::LimitClauseContext * ctx) override;
+
 //orderInformation
     antlrcpp::Any visitOrderInformation(SQLGrammarParser::OrderInformationContext * ctx) override;
 

test/api/cli/sql/SQLTest.cpp

@@ -103,5 +103,6 @@ MAKE_TEST_CASE("agg_sum", 1)
 
 MAKE_TEST_CASE("reuseString", 2)
 
+MAKE_TEST_CASE("limit", 1)
 
 // TODO Use the scripts testing failure cases.

test/api/cli/sql/limit_1.daphne

@@ -0,0 +1,13 @@
+# Selecting columns a and b from frame and only output the first 5 rows.
+
+f = createFrame(
+    [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
+    [5, 4, 3, 2, 1, 9, 8, 7, 6, 5],
+    "a", "b"
+);
+
+registerView("f", f);
+
+res = sql("SELECT f.a, f.b FROM f LIMIT 5;");
+
+print(res);

test/api/cli/sql/limit_1.txt

@@ -0,0 +1,6 @@
+Frame(5x2, [f.a:int64_t, f.b:int64_t])
+0 5
+1 4
+2 3
+3 2
+4 1