table: fix data race in select builder usage

When table is used with SelectBuilder it triggers data race on Where()
condition usage.

This change copies underlining slices on table creation to allow safe
concurrent usage of the table.

table/table.go

@@ -45,7 +45,8 @@ func New(m Metadata) *Table { // nolint: gocritic
 	for _, k := range m.SortKey {
 		t.primaryKeyCmp = append(t.primaryKeyCmp, qb.Eq(k))
 	}
-	t.partKeyCmp = t.primaryKeyCmp[:len(t.metadata.PartKey)]
+	t.partKeyCmp = make([]qb.Cmp, len(m.PartKey))
+	copy(t.partKeyCmp, t.primaryKeyCmp[:len(t.metadata.PartKey)])
 
 	// prepare get stmt
 	t.get.stmt, t.get.names = qb.Select(m.Name).Where(t.primaryKeyCmp...).ToCql()

table/table_test.go

@@ -5,9 +5,11 @@
 package table
 
 import (
+	"sync"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
+	"github.com/scylladb/gocqlx/qb"
 )
 
 func TestTableGet(t *testing.T) {
@@ -219,3 +221,59 @@ func TestTableDelete(t *testing.T) {
 		}
 	}
 }
+
+func TestTableConcurrentUsage(t *testing.T) {
+	table := []struct {
+		Name string
+		M    Metadata
+		C    []string
+		N    []string
+		S    string
+	}{
+		{
+			Name: "Full select",
+			M: Metadata{
+				Name:    "table",
+				Columns: []string{"a", "b", "c", "d"},
+				PartKey: []string{"a"},
+				SortKey: []string{"b"},
+			},
+			N: []string{"a", "b"},
+			S: "SELECT * FROM table WHERE a=? AND b=? ",
+		},
+		{
+			Name: "Sub select",
+			M: Metadata{
+				Name:    "table",
+				Columns: []string{"a", "b", "c", "d"},
+				PartKey: []string{"a"},
+				SortKey: []string{"b"},
+			},
+			C: []string{"d"},
+			N: []string{"a", "b"},
+			S: "SELECT d FROM table WHERE a=? AND b=? ",
+		},
+	}
+
+	parallelCount := 3
+	// run SelectBuilder on the data set in parallel
+	for _, test := range table {
+		var wg sync.WaitGroup
+		testTable := New(test.M)
+		wg.Add(parallelCount)
+		for i := 0; i < parallelCount; i++ {
+			go func() {
+				defer wg.Done()
+				stmt, names := testTable.SelectBuilder(test.C...).
+					Where(qb.Eq("b")).ToCql()
+				if diff := cmp.Diff(test.S, stmt); diff != "" {
+					t.Error(diff)
+				}
+				if diff := cmp.Diff(test.N, names); diff != "" {
+					t.Error(diff, names)
+				}
+			}()
+		}
+		wg.Wait()
+	}
+}