use group by instead of distinct when possible

tools/dbutils/select.go

@@ -0,0 +1,18 @@
+package dbutils
+
+import "regexp"
+
+// Regexp for columns and tables (the same as the one in dbx).
+var selectRegex = regexp.MustCompile(`(?i:\s+as\s+|\s+)([\w\-_\.]+)$`)
+
+// AliasOrIdentifier returns the alias from a column or table identifier,
+// Returns the identifier unmodified if no alias was found.
+func AliasOrIdentifier(columnOrTableIdentifier string) string {
+	matches := selectRegex.FindStringSubmatch(columnOrTableIdentifier)
+
+	if len(matches) > 0 && matches[1] != "" {
+		return matches[1]
+	}
+
+	return columnOrTableIdentifier
+}

tools/dbutils/select_test.go

@@ -0,0 +1,38 @@
+package dbutils_test
+
+import (
+	"testing"
+
+	"github.com/pocketbase/pocketbase/tools/dbutils"
+)
+
+func TestAliasOrIdentifier(t *testing.T) {
+	scenarios := []struct {
+		value    string
+		expected string
+	}{
+		{"", ""},
+		{"abc", "abc"},
+		{"abc  ", "abc  "}, // return unmodified
+		{"abc.def", "abc.def"},
+		{"abc.123 def", "def"},
+		{"abc.123 as def.456", "def.456"},
+		{"(abc) def", "def"},
+		{"(abc) as def", "def"},
+		{"abc   def", "def"},
+		{"abc as   def", "def"},
+		// technically invalid identifier but consistent with the dbx regex matching
+		{"a b c d", "d"},
+		{"a b c as d", "d"},
+	}
+
+	for _, s := range scenarios {
+		t.Run(s.value, func(t *testing.T) {
+			result := dbutils.AliasOrIdentifier(s.value)
+
+			if result != s.expected {
+				t.Fatalf("Expected\n%v\ngot\n%v", s.expected, result)
+			}
+		})
+	}
+}