From 7154635629bb67cacfa59617ea086de94a0f36a2 Mon Sep 17 00:00:00 2001
From: Antonio Navarro Perez <antnavper@gmail.com>
Date: Fri, 10 Feb 2017 17:27:47 +0100
Subject: [PATCH] expression: Add regexp support (#105)

---
 sql/expression/comparison.go      | 49 ++++++++++++++++++++++++---
 sql/expression/comparison_test.go | 55 +++++++++++++++++++++++++++++++
 sql/parse/parse.go                |  2 ++
 sql/parse/parse_test.go           | 12 +++++++
 4 files changed, 114 insertions(+), 4 deletions(-)

diff --git a/sql/expression/comparison.go b/sql/expression/comparison.go
index 79a9a4751..e82c38cf0 100644
--- a/sql/expression/comparison.go
+++ b/sql/expression/comparison.go
@@ -2,6 +2,7 @@ package expression
 
 import (
 	"fmt"
+	"regexp"
 
 	"github.com/gitql/gitql/sql"
 )
@@ -42,6 +43,50 @@ func (c *Equals) TransformUp(f func(sql.Expression) sql.Expression) sql.Expressi
 	return f(NewEquals(lc, rc))
 }
 
+func (e Equals) Name() string {
+	return e.Left.Name() + "==" + e.Right.Name()
+}
+
+type Regexp struct {
+	Comparison
+}
+
+func NewRegexp(left sql.Expression, right sql.Expression) *Regexp {
+	// FIXME: enable this again
+	// checkEqualTypes(left, right)
+	return &Regexp{Comparison{BinaryExpression{left, right}, left.Type()}}
+}
+
+func (e Regexp) Eval(row sql.Row) interface{} {
+	l := e.Left.Eval(row)
+	r := e.Right.Eval(row)
+
+	sl, okl := l.(string)
+	sr, okr := r.(string)
+
+	if !okl || !okr {
+		return e.ChildType.Compare(l, r) == 0
+	}
+
+	reg, err := regexp.Compile(sr)
+	if err != nil {
+		return false
+	}
+
+	return reg.MatchString(sl)
+}
+
+func (c *Regexp) TransformUp(f func(sql.Expression) sql.Expression) sql.Expression {
+	lc := c.BinaryExpression.Left.TransformUp(f)
+	rc := c.BinaryExpression.Right.TransformUp(f)
+
+	return f(NewRegexp(lc, rc))
+}
+
+func (e Regexp) Name() string {
+	return e.Left.Name() + " REGEXP " + e.Right.Name()
+}
+
 type GreaterThan struct {
 	Comparison
 }
@@ -139,7 +184,3 @@ func checkEqualTypes(a sql.Expression, b sql.Expression) {
 		panic(fmt.Errorf("both types should be equal: %v and %v\n", a, b))
 	}
 }
-
-func (e Equals) Name() string {
-	return e.Left.Name() + "==" + e.Right.Name()
-}
diff --git a/sql/expression/comparison_test.go b/sql/expression/comparison_test.go
index 63d90ce2c..8ca2ab693 100644
--- a/sql/expression/comparison_test.go
+++ b/sql/expression/comparison_test.go
@@ -12,6 +12,8 @@ const (
 	testEqual   = 1
 	testLess    = 2
 	testGreater = 3
+	testRegexp    = 4
+	testNotRegexp = 5
 )
 
 var comparisonCases = map[sql.Type]map[int][][]interface{}{
@@ -45,6 +47,33 @@ var comparisonCases = map[sql.Type]map[int][][]interface{}{
 	},
 }
 
+var likeComparisonCases = map[sql.Type]map[int][][]interface{}{
+	sql.String: {
+		testRegexp: {
+			{"foobar", ".*bar"},
+			{"foobarfoo", ".*bar.*"},
+			{"bar", "bar"},
+			{"barfoo", "bar.*"},
+		},
+		testNotRegexp: {
+			{"foobara", ".*bar$"},
+			{"foofoo", ".*bar.*"},
+			{"bara", "bar$"},
+			{"abarfoo", "^bar.*"},
+		},
+	},
+	sql.Integer: {
+		testRegexp: {
+			{int32(1), int32(1)},
+			{int32(0), int32(0)},
+		},
+		testNotRegexp: {
+			{int32(-1), int32(0)},
+			{int32(1), int32(2)},
+		},
+	},
+}
+
 func TestComparisons_Equals(t *testing.T) {
 	assert := require.New(t)
 	for resultType, cmpCase := range comparisonCases {
@@ -122,3 +151,29 @@ func TestComparisons_GreaterThan(t *testing.T) {
 		}
 	}
 }
+
+func TestComparisons_Regexp(t *testing.T) {
+	assert := require.New(t)
+	for resultType, cmpCase := range likeComparisonCases {
+		get0 := NewGetField(0, resultType, "col1")
+		assert.NotNil(get0)
+		get1 := NewGetField(1, resultType, "col2")
+		assert.NotNil(get1)
+		eq := NewRegexp(get0, get1)
+		assert.NotNil(eq)
+		assert.Equal(sql.Boolean, eq.Type())
+		for cmpResult, cases := range cmpCase {
+			for _, pair := range cases {
+				row := sql.NewRow(pair[0], pair[1])
+				assert.NotNil(row)
+				cmp := eq.Eval(row)
+				assert.NotNil(cmp)
+				if cmpResult == testRegexp {
+					assert.Equal(true, cmp)
+				} else {
+					assert.Equal(false, cmp)
+				}
+			}
+		}
+	}
+}
diff --git a/sql/parse/parse.go b/sql/parse/parse.go
index bf3c12b2b..f51856b64 100644
--- a/sql/parse/parse.go
+++ b/sql/parse/parse.go
@@ -306,6 +306,8 @@ func comparisonExprToExpression(c *sqlparser.ComparisonExpr) (sql.Expression,
 	switch c.Operator {
 	default:
 		return nil, errUnsupportedFeature(c.Operator)
+	case sqlparser.RegexpStr:
+		return expression.NewRegexp(left, right), nil
 	case sqlparser.EqualStr:
 		return expression.NewEquals(left, right), nil
 	case sqlparser.LessThanStr:
diff --git a/sql/parse/parse_test.go b/sql/parse/parse_test.go
index 56acf42fc..41f29bfe9 100644
--- a/sql/parse/parse_test.go
+++ b/sql/parse/parse_test.go
@@ -161,6 +161,18 @@ var fixtures = map[string]sql.Node{
 		[]sql.Expression{},
 		plan.NewUnresolvedTable("t1"),
 	),
+	`SELECT a FROM t1 where a regexp '.*test.*';`: plan.NewProject(
+		[]sql.Expression{
+			expression.NewUnresolvedColumn("a"),
+		},
+		plan.NewFilter(
+			expression.NewRegexp(
+				expression.NewUnresolvedColumn("a"),
+				expression.NewLiteral(".*test.*", sql.String),
+			),
+			plan.NewUnresolvedTable("t1"),
+		),
+	),
 }
 
 func TestParse(t *testing.T) {