Merge pull request #649 from upper/refactor-memory-and-speed-optimizations

optimize `prepareQueryForDisplay`

internal/sqlbuilder/builder.go

@@ -29,7 +29,6 @@ import (
 	"fmt"
 	"log"
 	"reflect"
-	"regexp"
 	"sort"
 	"strconv"
 	"strings"
@@ -72,10 +71,6 @@ type fieldValue struct {
 	values []interface{}
 }
 
-var (
-	reInvisibleChars = regexp.MustCompile(`[\s\r\n\t]+`)
-)
-
 var (
 	sqlPlaceholder = exql.RawValue(`?`)
 )
@@ -347,11 +342,10 @@ func Map(item interface{}, options *MapOptions) ([]string, []interface{}, error)
 }
 
 func columnFragments(columns []interface{}) ([]exql.Fragment, []interface{}, error) {
-	l := len(columns)
-	f := make([]exql.Fragment, l)
+	f := make([]exql.Fragment, len(columns))
 	args := []interface{}{}
 
-	for i := 0; i < l; i++ {
+	for i := range columns {
 		switch v := columns[i].(type) {
 		case compilable:
 			c, err := v.Compile()
@@ -393,19 +387,44 @@ func columnFragments(columns []interface{}) ([]exql.Fragment, []interface{}, err
 	return f, args, nil
 }
 
-func prepareQueryForDisplay(in string) (out string) {
-	j := 1
-	for i := range in {
-		if in[i] == '?' {
-			out = out + "$" + strconv.Itoa(j)
-			j++
+func prepareQueryForDisplay(in string) string {
+	out := make([]byte, 0, len(in))
+
+	offset := 0
+	whitespace := true
+	placeholders := 1
+
+	for i := 0; i < len(in); i++ {
+		if in[i] == ' ' || in[i] == '\r' || in[i] == '\n' || in[i] == '\t' {
+			if whitespace {
+				offset = i
 			} else {
-			out = out + string(in[i])
+				whitespace = true
+				out = append(out, in[offset:i]...)
+				offset = i
 			}
+			continue
 		}
+		if whitespace {
+			whitespace = false
+			if len(out) > 0 {
+				out = append(out, ' ')
+			}
+			offset = i
+		}
+		if in[i] == '?' {
+			out = append(out, in[offset:i]...)
+			offset = i + 1
 
-	out = reInvisibleChars.ReplaceAllString(out, ` `)
-	return strings.TrimSpace(out)
+			out = append(out, '$')
+			out = append(out, strconv.Itoa(placeholders)...)
+			placeholders++
+		}
+	}
+	if !whitespace {
+		out = append(out, in[offset:len(in)]...)
+	}
+	return string(out)
 }
 
 func (iter *iterator) NextScan(dst ...interface{}) error {

internal/sqlbuilder/builder_test.go

@@ -2,6 +2,7 @@ package sqlbuilder
 
 import (
 	"fmt"
+	"regexp"
 	"strings"
 	"testing"
 
@@ -9,6 +10,10 @@ import (
 	db "github.com/upper/db/v4"
 )
 
+var (
+	reInvisibleChars = regexp.MustCompile(`[\s\r\n\t]+`)
+)
+
 func TestSelect(t *testing.T) {
 
 	b := &sqlBuilder{t: newTemplateWithUtils(&testTemplate)}

internal/sqlbuilder/placeholder_test.go

@@ -7,6 +7,69 @@ import (
 	db "github.com/upper/db/v4"
 )
 
+func TestPrepareForDisplay(t *testing.T) {
+	samples := []struct {
+		In  string
+		Out string
+	}{
+		{
+			In:  "12345",
+			Out: "12345",
+		},
+		{
+			In:  "\r\n\t12345",
+			Out: "12345",
+		},
+		{
+			In:  "12345\r\n\t",
+			Out: "12345",
+		},
+		{
+			In:  "\r\n\t1\r2\n3\t4\r5\r\n\t",
+			Out: "1 2 3 4 5",
+		},
+		{
+			In:  "\r\n    \t  1\r 2\n 3\t 4\r    5\r    \n\t",
+			Out: "1 2 3 4 5",
+		},
+		{
+			In:  "\r\n    \t  11\r 22\n 33\t    44 \r      55",
+			Out: "11 22 33 44 55",
+		},
+		{
+			In:  "11\r    22\n 33\t       44 \r      55",
+			Out: "11 22 33 44 55",
+		},
+		{
+			In:  "1  2  3 4 5",
+			Out: "1 2 3 4 5",
+		},
+		{
+			In:  "?",
+			Out: "$1",
+		},
+		{
+			In:  "? ?",
+			Out: "$1 $2",
+		},
+		{
+			In:  "?  ?    ?",
+			Out: "$1 $2 $3",
+		},
+		{
+			In:  " ?  ?    ?        ",
+			Out: "$1 $2 $3",
+		},
+		{
+			In:  "???",
+			Out: "$1$2$3",
+		},
+	}
+	for _, sample := range samples {
+		assert.Equal(t, sample.Out, prepareQueryForDisplay(sample.In))
+	}
+}
+
 func TestPlaceholderSimple(t *testing.T) {
 	{
 		ret, _ := Preprocess("?", []interface{}{1})