Make sure table stub is valid as a pilosa.Index name (#2306)

We use part of the dax.TableName in the pilosa.Index.Name.
This just ensure that we don't let invalid characters get through.

dax/table.go

@@ -3,6 +3,7 @@ package dax
 import (
 	"crypto/rand"
 	"fmt"
+	"regexp"
 	"strings"
 	"time"
 
@@ -177,8 +178,9 @@ func (t *Table) CreateID() (TableID, error) {
 	//
 	// In order to avoid creating an ID with a double underscore, we remove all
 	// underscores from the original table name (because that's what we use in
-	// TableKey as a delimiter).
-	stub := strings.ReplaceAll(string(t.Name), "_", "")
+	// TableKey as a delimiter). In addition to that, we remove any other
+	// characters which are not valid as a pilosa indes name.
+	stub := regexp.MustCompile(`[^a-z0-9-]+`).ReplaceAllString(strings.ToLower(string(t.Name)), "")
 	if len(stub) > 10 {
 		stub = stub[:10]
 	}

dax/table_test.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"sort"
+	"strings"
 	"testing"
 	"time"
 
@@ -208,6 +209,55 @@ func TestTable(t *testing.T) {
 	})
 
 	t.Run("Table", func(t *testing.T) {
+		// CleanStub makes sure that the portion of the dax.TableName that we
+		// use in the pilosa.Index.Name is actually valid.
+		t.Run("CleanStub", func(t *testing.T) {
+			tests := []struct {
+				name    dax.TableName
+				expStub string
+			}{
+				{
+					name:    "",
+					expStub: "",
+				},
+				{
+					name:    "foo",
+					expStub: "foo",
+				},
+				{
+					name:    "AbCdEfG1234",
+					expStub: "abcdefg123",
+				},
+				{
+					name:    "foo_bar_",
+					expStub: "foobar",
+				},
+				{
+					name:    "!!!!!!!",
+					expStub: "",
+				},
+				{
+					name:    "long1234567890",
+					expStub: "long123456",
+				},
+				{
+					name:    "&&&&&&&&&&&&&&valid_stuff",
+					expStub: "validstuff",
+				},
+			}
+
+			for i, test := range tests {
+				t.Run(fmt.Sprintf("test-%d", i), func(t *testing.T) {
+					n := dax.NewTable(test.name)
+					assert.Empty(t, n.ID)
+					n.CreateID()
+
+					parts := strings.Split(string(n.ID), "_")
+					assert.Equal(t, test.expStub, parts[0])
+				})
+			}
+		})
+
 		t.Run("RandomID", func(t *testing.T) {
 			n := dax.NewTable(tableName)
 			assert.Empty(t, n.ID)