Add noop hash func

Author: prashanthpai

hash.go

@@ -0,0 +1,43 @@
+package sqlcache
+
+import (
+	"database/sql/driver"
+	"fmt"
+	"strconv"
+	"strings"
+	"unicode"
+
+	"github.com/mitchellh/hashstructure"
+)
+
+func defaultHashFunc(query string, args []driver.NamedValue) (string, error) {
+	u64, err := hashstructure.Hash(struct {
+		Query string
+		Args  []driver.NamedValue
+	}{
+		Query: query,
+		Args:  args,
+	}, nil)
+	if err != nil {
+		return "", err
+	}
+
+	key := fmt.Sprintf("q%da%dh%s", len(query), len(args), strconv.FormatUint(u64, 10))
+	return key, nil
+}
+
+// NoopHash returns a string representation of the query and args. Whitespaces
+// in the query string is stripped off.
+func NoopHash(query string, args []driver.NamedValue) (string, error) {
+	var b strings.Builder
+	b.Grow(len(query) + len(args)*10) // arbitrary
+	for _, ch := range query {
+		if !unicode.IsSpace(ch) {
+			b.WriteRune(ch)
+		}
+	}
+	b.WriteRune(':')
+	b.WriteString(fmt.Sprintf("%v", args))
+
+	return b.String(), nil
+}

hash_test.go

@@ -0,0 +1,39 @@
+package sqlcache
+
+import (
+	"database/sql/driver"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestNoopHash(t *testing.T) {
+	assert := require.New(t)
+
+	tcs := []struct {
+		query    string
+		args     []driver.NamedValue
+		expected string
+	}{
+		{
+			query: `
+			-- @cache-ttl 5
+			-- @cache-max-rows 10
+			SELECT name, pages FROM books WHERE pages > $1
+			`,
+			args: []driver.NamedValue{
+				{
+					Ordinal: 1,
+					Value:   10,
+				},
+			},
+			expected: "--@cache-ttl5--@cache-max-rows10SELECTname,pagesFROMbooksWHEREpages>$1:[{ 1 10}]",
+		},
+	}
+
+	for _, tc := range tcs {
+		h, err := NoopHash(tc.query, tc.args)
+		assert.Nil(err)
+		assert.Equal(tc.expected, h)
+	}
+}

interceptor.go

@@ -4,11 +4,9 @@ import (
 	"context"
 	"database/sql/driver"
 	"fmt"
-	"strconv"
 	"sync/atomic"
 	"time"
 
-	"github.com/mitchellh/hashstructure"
 	"github.com/ngrok/sqlmw"
 	"github.com/prashanthpai/sqlcache/cache"
 )
@@ -26,6 +24,7 @@ type Config struct {
 	OnError func(error)
 	// HashFunc can be optionally set to provide a custom hashing function. By
 	// default sqlcache uses mitchellh/hashstructure which internally uses FNV.
+	// If hash collision is a concern to you, consider using NoopHash.
 	HashFunc func(query string, args []driver.NamedValue) (string, error)
 }
 
@@ -185,22 +184,6 @@ func (i *Interceptor) checkCache(hash string) driver.Rows {
 	}
 }
 
-func defaultHashFunc(query string, args []driver.NamedValue) (string, error) {
-	u64, err := hashstructure.Hash(struct {
-		Query string
-		Args  []driver.NamedValue
-	}{
-		Query: query,
-		Args:  args,
-	}, nil)
-	if err != nil {
-		return "", err
-	}
-
-	key := fmt.Sprintf("q%da%dh%s", len(query), len(args), strconv.FormatUint(u64, 10))
-	return key, nil
-}
-
 // Stats contains sqlcache statistics.
 type Stats struct {
 	Hits   uint64