function: implement regexp_matches

Signed-off-by: Miguel Molina <miguel@erizocosmi.co>

README.md

@@ -103,6 +103,7 @@ We support and actively test against certain third-party clients to ensure compa
 |`NOW()`|Returns the current timestamp.|
 |`NULLIF(expr1, expr2)`|Returns NULL if expr1 = expr2 is true, otherwise returns expr1.|
 |`POW(X, Y)`|Returns the value of X raised to the power of Y.|
+|`REGEXP_MATCHES(text, pattern, [flags])`|Returns an array with the matches of the pattern in the given text. Flags can be given to control certain behaviours of the regular expression. Currently, only the `i` flag is supported, to make the comparison case insensitive.|
 |`REPEAT(str, count)`|Returns a string consisting of the string str repeated count times.|
 |`REPLACE(str,from_str,to_str)`|Returns the string str with all occurrences of the string from_str replaced by the string to_str.|
 |`REVERSE(str)`|Returns the string str with the order of the characters reversed.|

engine_test.go

@@ -1454,6 +1454,18 @@ var queries = []struct {
 		ORDER BY table_type, table_schema, table_name`,
 		[]sql.Row{{"mydb", "mytable", "TABLE"}},
 	},
+	{
+		`SELECT REGEXP_MATCHES("bopbeepbop", "bop")`,
+		[]sql.Row{{[]interface{}{"bop", "bop"}}},
+	},
+	{
+		`SELECT EXPLODE(REGEXP_MATCHES("bopbeepbop", "bop"))`,
+		[]sql.Row{{"bop"}, {"bop"}},
+	},
+	{
+		`SELECT EXPLODE(REGEXP_MATCHES("helloworld", "bop"))`,
+		[]sql.Row{},
+	},
 }
 
 func TestQueries(t *testing.T) {

sql/expression/function/regexp_matches.go

@@ -0,0 +1,184 @@
+package function
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+
+	"github.com/src-d/go-mysql-server/sql"
+	"github.com/src-d/go-mysql-server/sql/expression"
+	errors "gopkg.in/src-d/go-errors.v1"
+)
+
+// RegexpMatches returns the matches of a regular expression.
+type RegexpMatches struct {
+	Text    sql.Expression
+	Pattern sql.Expression
+	Flags   sql.Expression
+
+	cacheable bool
+	re        *regexp.Regexp
+}
+
+// NewRegexpMatches creates a new RegexpMatches expression.
+func NewRegexpMatches(args ...sql.Expression) (sql.Expression, error) {
+	var r RegexpMatches
+	switch len(args) {
+	case 3:
+		r.Flags = args[2]
+		fallthrough
+	case 2:
+		r.Text = args[0]
+		r.Pattern = args[1]
+	default:
+		return nil, sql.ErrInvalidArgumentNumber.New("regexp_matches", "2 or 3", len(args))
+	}
+
+	if canBeCached(r.Pattern) && (r.Flags == nil || canBeCached(r.Flags)) {
+		r.cacheable = true
+	}
+
+	return &r, nil
+}
+
+// Type implements the sql.Expression interface.
+func (r *RegexpMatches) Type() sql.Type { return sql.Array(sql.Text) }
+
+// IsNullable implements the sql.Expression interface.
+func (r *RegexpMatches) IsNullable() bool { return true }
+
+// Children implements the sql.Expression interface.
+func (r *RegexpMatches) Children() []sql.Expression {
+	var result = []sql.Expression{r.Text, r.Pattern}
+	if r.Flags != nil {
+		result = append(result, r.Flags)
+	}
+	return result
+}
+
+// Resolved implements the sql.Expression interface.
+func (r *RegexpMatches) Resolved() bool {
+	return r.Text.Resolved() && r.Pattern.Resolved() && (r.Flags == nil || r.Flags.Resolved())
+}
+
+// WithChildren implements the sql.Expression interface.
+func (r *RegexpMatches) WithChildren(children ...sql.Expression) (sql.Expression, error) {
+	required := 2
+	if r.Flags != nil {
+		required = 3
+	}
+
+	if len(children) != required {
+		return nil, sql.ErrInvalidChildrenNumber.New(r, len(children), required)
+	}
+
+	return NewRegexpMatches(children...)
+}
+
+func (r *RegexpMatches) String() string {
+	var args []string
+	for _, e := range r.Children() {
+		args = append(args, e.String())
+	}
+	return fmt.Sprintf("regexp_matches(%s)", strings.Join(args, ", "))
+}
+
+// Eval implements the sql.Expression interface.
+func (r *RegexpMatches) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
+	span, ctx := ctx.Span("function.RegexpMatches")
+	defer span.Finish()
+
+	var re *regexp.Regexp
+	var err error
+	if r.cacheable {
+		if r.re == nil {
+			r.re, err = r.compileRegex(ctx, nil)
+			if err != nil {
+				return nil, err
+			}
+		}
+		re = r.re
+	} else {
+		re, err = r.compileRegex(ctx, row)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	text, err := r.Text.Eval(ctx, row)
+	if err != nil {
+		return nil, err
+	}
+
+	text, err = sql.Text.Convert(text)
+	if err != nil {
+		return nil, err
+	}
+
+	matches := re.FindAllStringSubmatch(text.(string), -1)
+	if len(matches) == 0 {
+		return nil, nil
+	}
+
+	var result []interface{}
+	for _, m := range matches {
+		for _, sm := range m {
+			result = append(result, sm)
+		}
+	}
+
+	return result, nil
+}
+
+func (r *RegexpMatches) compileRegex(ctx *sql.Context, row sql.Row) (*regexp.Regexp, error) {
+	pattern, err := r.Pattern.Eval(ctx, row)
+	if err != nil {
+		return nil, err
+	}
+
+	pattern, err = sql.Text.Convert(pattern)
+	if err != nil {
+		return nil, err
+	}
+
+	var flags string
+	if r.Flags != nil {
+		f, err := r.Flags.Eval(ctx, row)
+		if err != nil {
+			return nil, err
+		}
+
+		f, err = sql.Text.Convert(f)
+		if err != nil {
+			return nil, err
+		}
+
+		flags = f.(string)
+		for _, f := range flags {
+			if !validRegexpFlags[f] {
+				return nil, errInvalidRegexpFlag.New(f)
+			}
+		}
+
+		flags = fmt.Sprintf("(?%s)", flags)
+	}
+
+	return regexp.Compile(flags + pattern.(string))
+}
+
+var errInvalidRegexpFlag = errors.NewKind("invalid regexp flag: %v")
+
+var validRegexpFlags = map[rune]bool{
+	'i': true,
+}
+
+func canBeCached(e sql.Expression) bool {
+	var hasCols bool
+	expression.Inspect(e, func(e sql.Expression) bool {
+		if _, ok := e.(*expression.GetField); ok {
+			hasCols = true
+		}
+		return true
+	})
+	return !hasCols
+}

sql/expression/function/regexp_matches_test.go

@@ -0,0 +1,111 @@
+package function
+
+import (
+	"testing"
+
+	"github.com/src-d/go-mysql-server/sql"
+	"github.com/src-d/go-mysql-server/sql/expression"
+	"github.com/stretchr/testify/require"
+
+	errors "gopkg.in/src-d/go-errors.v1"
+)
+
+func TestRegexpMatches(t *testing.T) {
+	testCases := []struct {
+		pattern  string
+		text     string
+		flags    string
+		expected interface{}
+		err      *errors.Kind
+	}{
+		{
+			`^foobar(.*)bye$`,
+			"foobarhellobye",
+			"",
+			[]interface{}{"foobarhellobye", "hello"},
+			nil,
+		},
+		{
+			"bop",
+			"bopbeepbop",
+			"",
+			[]interface{}{"bop", "bop"},
+			nil,
+		},
+		{
+			"bop",
+			"bopbeepBop",
+			"i",
+			[]interface{}{"bop", "Bop"},
+			nil,
+		},
+		{
+			"bop",
+			"helloworld",
+			"",
+			nil,
+			nil,
+		},
+		{
+			"bop",
+			"bopbeepBop",
+			"ix",
+			nil,
+			errInvalidRegexpFlag,
+		},
+	}
+
+	t.Run("cacheable", func(t *testing.T) {
+		for _, tt := range testCases {
+			var flags sql.Expression
+			if tt.flags != "" {
+				flags = expression.NewLiteral(tt.flags, sql.Text)
+			}
+			f, err := NewRegexpMatches(
+				expression.NewLiteral(tt.text, sql.Text),
+				expression.NewLiteral(tt.pattern, sql.Text),
+				flags,
+			)
+			require.NoError(t, err)
+
+			t.Run(f.String(), func(t *testing.T) {
+				require := require.New(t)
+				result, err := f.Eval(sql.NewEmptyContext(), nil)
+				if tt.err == nil {
+					require.NoError(err)
+					require.Equal(tt.expected, result)
+				} else {
+					require.Error(err)
+					require.True(tt.err.Is(err))
+				}
+			})
+		}
+	})
+
+	t.Run("not cacheable", func(t *testing.T) {
+		for _, tt := range testCases {
+			var flags sql.Expression
+			if tt.flags != "" {
+				flags = expression.NewGetField(2, sql.Text, "x", false)
+			}
+			f, err := NewRegexpMatches(
+				expression.NewGetField(0, sql.Text, "x", false),
+				expression.NewGetField(1, sql.Text, "x", false),
+				flags,
+			)
+			require.NoError(t, err)
+
+			t.Run(f.String(), func(t *testing.T) {
+				require := require.New(t)
+				result, err := f.Eval(sql.NewEmptyContext(), sql.Row{tt.text, tt.pattern, tt.flags})
+				if tt.err == nil {
+					require.NoError(err)
+					require.Equal(tt.expected, result)
+				} else {
+					require.Error(err)
+					require.True(tt.err.Is(err))
+				}
+			})
+		}
+	})
+}

sql/expression/function/registry.go

@@ -98,4 +98,5 @@ var Defaults = []sql.Function{
 	sql.Function1{Name: "char_length", Fn: NewCharLength},
 	sql.Function1{Name: "character_length", Fn: NewCharLength},
 	sql.Function1{Name: "explode", Fn: NewExplode},
+	sql.FunctionN{Name: "regexp_matches", Fn: NewRegexpMatches},
 }