fix: support information_schema.sequences (#708)

Adds support for information_schema.sequences using a common table expression. The CTE always returns zero rows and is there purely for compatibility reasons. Towards #705

Author: olavloite

src/main/java/com/google/cloud/spanner/pgadapter/statements/PgCatalog.java

@@ -27,6 +27,7 @@
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import java.util.HashSet;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;
@@ -66,6 +67,9 @@ public class PgCatalog {
  .put(
  new TableOrIndexName(null, "pg_sequences"),
  new TableOrIndexName(null, "pg_sequences"))
+ .put(
+ new TableOrIndexName("information_schema", "sequences"),
+ new TableOrIndexName(null, "pg_information_schema_sequences"))
  .put(
  new TableOrIndexName("pg_catalog", "pg_settings"),
  new TableOrIndexName(null, "pg_settings"))
@@ -95,7 +99,9 @@ public class PgCatalog {
  new TableOrIndexName(null, "pg_range"), new PgRange(),
  new TableOrIndexName(null, "pg_type"), new PgType(),
  new TableOrIndexName(null, "pg_sequence"), new PgSequence(),
- new TableOrIndexName(null, "pg_sequences"), new PgSequences());
+ new TableOrIndexName(null, "pg_sequences"), new PgSequences(),
+ new TableOrIndexName(null, "pg_information_schema_sequences"),
+ new InformationSchemaSequences());
  private final SessionState sessionState;
 
  public PgCatalog(@Nonnull SessionState sessionState, @Nonnull WellKnownClient wellKnownClient) {
@@ -130,7 +136,8 @@ public PgCatalog(@Nonnull SessionState sessionState, @Nonnull WellKnownClient we
  /** Replace supported pg_catalog tables with Common Table Expressions. */
  public Statement replacePgCatalogTables(Statement statement) {
  // Only replace tables if the statement contains at least one of the known prefixes.
- if (checkPrefixes.stream().noneMatch(prefix -> statement.getSql().contains(prefix))) {
+ String sql = statement.getSql().toLowerCase(Locale.ENGLISH);
+ if (checkPrefixes.stream().noneMatch(sql::contains)) {
  return statement;
  }
 
@@ -514,4 +521,22 @@ public String getTableExpression() {
  return PG_SEQUENCE_CTE;
  }
  }
+
+ private static class InformationSchemaSequences implements PgCatalogTable {
+ // The name of this CTE is a little strange, but that is to make sure it does not accidentally
+ // collide with any user-defined table or view.
+ private static final String INFORMATION_SCHEMA_SEQUENCES_CTE =
+ "pg_information_schema_sequences as (\n"
+ + "select * from ("
+ + "select ''::varchar as sequence_catalog, ''::varchar as sequence_schema, ''::varchar as sequence_name, "
+ + "''::varchar as data_type, 0::bigint as numeric_precision, 0::bigint as numeric_precision_radix, "
+ + "''::varchar as start_value, ''::varchar as minimum_value, ''::varchar as maximum_value, "
+ + "''::varchar as increment, 'NO'::varchar as cycle_option\n"
+ + ") seq where false)";
+
+ @Override
+ public String getTableExpression() {
+ return INFORMATION_SCHEMA_SEQUENCES_CTE;
+ }
+ }
 }

src/main/java/com/google/cloud/spanner/pgadapter/utils/ClientAutoDetector.java

@@ -60,7 +60,7 @@ public class ClientAutoDetector {
  SelectVersionStatement.INSTANCE,
  DjangoGetTableNamesStatement.INSTANCE);
  private static final ImmutableSet<String> DEFAULT_CHECK_PG_CATALOG_PREFIXES =
- ImmutableSet.of("pg_");
+ ImmutableSet.of("pg_", "information_schema.");
  public static final String PGBENCH_USAGE_HINT =
  "See https://github.com/GoogleCloudPlatform/pgadapter/blob/-/docs/pgbench.md for how to use pgbench with PGAdapter";
 

src/test/java/com/google/cloud/spanner/pgadapter/ITJdbcTest.java

@@ -224,6 +224,21 @@ public void testPgCatalogViews() throws SQLException {
  }
  }
 
+ @Test
+ public void testInformationSchemaViews() throws SQLException {
+ for (String view : new String[] {"sequences"}) {
+ try (Connection connection = DriverManager.getConnection(getConnectionUrl())) {
+ try (ResultSet resultSet =
+ connection.createStatement().executeQuery("SELECT * FROM INFORMATION_SCHEMA." + view)) {
+ while (resultSet.next()) {
+ assertNotNull(resultSet.getMetaData());
+ assertNotEquals(0, resultSet.getMetaData().getColumnCount());
+ }
+ }
+ }
+ }
+ }
+
  @Test
  public void testCreateTableIfNotExists() throws SQLException {
  try (Connection connection = DriverManager.getConnection(getConnectionUrl())) {