SQLite: Don't leak internal schema objects

Related #31201.

If creating custom primary key (like a string) in SQLite, it would also
create an internal index implicitly which named begin with "sqlite_".

It need to be hidden since the internal object names are reserved and
prohibited for public use.

See https://www.sqlite.org/fileformat2.html#intschema

Fixes #33320.

2 files changed, 5 insertions, 4 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
index 58e5138e02..24e7bc65fa 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
@@ -7,6 +7,10 @@ module ActiveRecord
         # Returns an array of indexes for the given table.
         def indexes(table_name)
           exec_query("PRAGMA index_list(#{quote_table_name(table_name)})", "SCHEMA").map do |row|
+            # Indexes SQLite creates implicitly for internal use start with "sqlite_".
+            # See https://www.sqlite.org/fileformat2.html#intschema
+            next if row["name"].starts_with?("sqlite_")
+
             index_sql = query_value(<<-SQL, "SCHEMA")
               SELECT sql
               FROM sqlite_master
@@ -40,7 +44,7 @@ module ActiveRecord
               where: where,
               orders: orders
             )
-          end
+          end.compact
         end
 
         def create_schema_dumper(options)
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 844af952c1..bee74dc33d 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -457,9 +457,6 @@ module ActiveRecord
         def copy_table_indexes(from, to, rename = {})
           indexes(from).each do |index|
             name = index.name
-            # indexes sqlite creates for internal use start with `sqlite_` and
-            # don't need to be copied
-            next if name.starts_with?("sqlite_")
             if to == "a#{from}"
               name = "t#{name}"
             elsif from == "a#{to}"