fix: support information_schema.sequences

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
GoogleCloudPlatform · Mar 3, 2023 · e1cf0cf · e1cf0cf
1 parent b2c1f1e
commit e1cf0cf
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Showing 3 changed files with 43 additions and 3 deletions.
diff --git a/src/main/java/com/google/cloud/spanner/pgadapter/statements/PgCatalog.java b/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;
+    }
+  }
 }
diff --git a/src/main/java/com/google/cloud/spanner/pgadapter/utils/ClientAutoDetector.java b/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";
 

diff --git a/src/test/java/com/google/cloud/spanner/pgadapter/ITJdbcTest.java b/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())) {