Repository: GoogleCloudPlatform/pgadapter
Pull request #1818 (2024-05-21 10:18:04)

deps: update dependency requests to <2.32.3
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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [requests](https://requests.readthedocs.io) ([source](https://togithub.com/psf/requests), [changelog](https://togithub.com/psf/requests/blob/master/HISTORY.md)) | `<2.32.0` -> `<2.32.3` | [![age](https://developer.mend.io/api/mc/badges/age/pypi/requests/2.32.2?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://developer.mend.io/api/mc/badges/adoption/pypi/requests/2.32.2?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://developer.mend.io/api/mc/badges/compatibility/pypi/requests/2.31.0/2.32.2?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/requests/2.31.0/2.32.2?slim=true)](https://docs.renovatebot.com/merge-confidence/) |

---

### Release Notes

<details>
<summary>psf/requests (requests)</summary>

### [`v2.32.2`](https://togithub.com/psf/requests/blob/HEAD/HISTORY.md#2322-2024-05-21)

[Compare Source](https://togithub.com/psf/requests/compare/v2.32.1...v2.32.2)

**Deprecations**

-   To provide a more stable migration for custom HTTPAdapters impacted
    by the CVE changes in 2.32.0, we've renamed `_get_connection` to
    a new public API, `get_connection_with_tls_context`. Existing custom
    HTTPAdapters will need to migrate their code to use this new API.
    `get_connection` is considered deprecated in all versions of Requests>=2.32.0.

    A minimal (2-line) example has been provided in the linked PR to ease
    migration, but we strongly urge users to evaluate if their custom adapter
    is subject to the same issue described in CVE-2024-35195. ([#&#8203;6710](https://togithub.com/psf/requests/issues/6710))

### [`v2.32.1`](https://togithub.com/psf/requests/blob/HEAD/HISTORY.md#2321-2024-05-20)

[Compare Source](https://togithub.com/psf/requests/compare/v2.32.0...v2.32.1)

**Bugfixes**

-   Add missing test certs to the sdist distributed on PyPI.

### [`v2.32.0`](https://togithub.com/psf/requests/blob/HEAD/HISTORY.md#2320-2024-05-20)

[Compare Source](https://togithub.com/psf/requests/compare/v2.31.0...v2.32.0)

**Security**

-   Fixed an issue where setting `verify=False` on the first request from a
    Session will cause subsequent requests to the *same origin* to also ignore
    cert verification, regardless of the value of `verify`.
    (https://github.com/psf/requests/security/advisories/GHSA-9wx4-h78v-vm56)

**Improvements**

-   `verify=True` now reuses a global SSLContext which should improve
    request time variance between first and subsequent requests. It should
    also minimize certificate load time on Windows systems when using a Python
    version built with OpenSSL 3.x. ([#&#8203;6667](https://togithub.com/psf/requests/issues/6667))
-   Requests now supports optional use of character detection
    (`chardet` or `charset_normalizer`) when repackaged or vendored.
    This enables `pip` and other projects to minimize their vendoring
    surface area. The `Response.text()` and `apparent_encoding` APIs
    will default to `utf-8` if neither library is present. ([#&#8203;6702](https://togithub.com/psf/requests/issues/6702))

**Bugfixes**

-   Fixed bug in length detection where emoji length was incorrectly
    calculated in the request content-length. ([#&#8203;6589](https://togithub.com/psf/requests/issues/6589))
-   Fixed deserialization bug in JSONDecodeError. ([#&#8203;6629](https://togithub.com/psf/requests/issues/6629))
-   Fixed bug where an extra leading `/` (path separator) could lead
    urllib3 to unnecessarily reparse the request URI. ([#&#8203;6644](https://togithub.com/psf/requests/issues/6644))

**Deprecations**

-   Requests has officially added support for CPython 3.12 ([#&#8203;6503](https://togithub.com/psf/requests/issues/6503))
-   Requests has officially added support for PyPy 3.9 and 3.10 ([#&#8203;6641](https://togithub.com/psf/requests/issues/6641))
-   Requests has officially dropped support for CPython 3.7 ([#&#8203;6642](https://togithub.com/psf/requests/issues/6642))
-   Requests has officially dropped support for PyPy 3.7 and 3.8 ([#&#8203;6641](https://togithub.com/psf/requests/issues/6641))

**Documentation**

-   Various typo fixes and doc improvements.

**Packaging**

-   Requests has started adopting some modern packaging practices.
    The source files for the projects (formerly `requests`) is now located
    in `src/requests` in the Requests sdist. ([#&#8203;6506](https://togithub.com/psf/requests/issues/6506))
-   Starting in Requests 2.33.0, Requests will migrate to a PEP 517 build system
    using `hatchling`. This should not impact the average user, but extremely old
    versions of packaging utilities may have issues with the new packaging format.

</details>

---

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---

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Patch:
diff --git a/.github/workflows/integration.yaml b/.github/workflows/integration.yaml
index 8195c7c3..a54be1fa 100644
--- a/.github/workflows/integration.yaml
+++ b/.github/workflows/integration.yaml
@@ -21,6 +21,7 @@ env:
   GOOGLE_CLOUD_INSTANCE: "pgadapter-testing"
   GOOGLE_CLOUD_DATABASE: "testdb_integration"
   GOOGLE_CLOUD_ENDPOINT: "spanner.googleapis.com"
+  PG_ADAPTER_DROP_STALE_DATABASES: true
 jobs:
   check-env:
     outputs:
diff --git a/benchmarks/tpcc/pom.xml b/benchmarks/tpcc/pom.xml
index 52b07a3a..c496d191 100644
--- a/benchmarks/tpcc/pom.xml
+++ b/benchmarks/tpcc/pom.xml
@@ -79,7 +79,7 @@
       <plugin>
         <groupId>com.spotify.fmt</groupId>
         <artifactId>fmt-maven-plugin</artifactId>
-        <version>2.21.1</version>
+        <version>2.23</version>
         <executions>
           <execution>
             <goals>
diff --git a/benchmarks/tpcc/src/main/java/com/google/cloud/pgadapter/tpcc/dataloader/NewOrderRowProducer.java b/benchmarks/tpcc/src/main/java/com/google/cloud/pgadapter/tpcc/dataloader/NewOrderRowProducer.java
index 2e9885fc..1680c02a 100644
--- a/benchmarks/tpcc/src/main/java/com/google/cloud/pgadapter/tpcc/dataloader/NewOrderRowProducer.java
+++ b/benchmarks/tpcc/src/main/java/com/google/cloud/pgadapter/tpcc/dataloader/NewOrderRowProducer.java
@@ -18,7 +18,8 @@ import com.google.common.collect.ImmutableList;
 
 class NewOrderRowProducer extends AbstractOrderedIdRowProducer {
   private static final String TABLE = "new_orders";
-  private static final String COLUMNS = """
+  private static final String COLUMNS =
+      """
     o_id,
     c_id,
     d_id,
diff --git a/samples/python/django/requirements.txt b/samples/python/django/requirements.txt
index 742372ee..9ae930a8 100644
--- a/samples/python/django/requirements.txt
+++ b/samples/python/django/requirements.txt
@@ -4,4 +4,4 @@ Django==5.0.6
 google==3.0.0
 google.auth==2.29.0
 testcontainers==4.5.0
-requests<2.32.0  # `requests` renamed `get_connection` to `_get_connection`, which is a method docker-py monkeypatches. See https://github.com/docker/docker-py/issues/3256 Should be able to un-pin when docker-py hotfix is out.
+requests==2.32.2
diff --git a/samples/python/psycopg3/requirements.txt b/samples/python/psycopg3/requirements.txt
index f80aadb4..bd798dba 100644
--- a/samples/python/psycopg3/requirements.txt
+++ b/samples/python/psycopg3/requirements.txt
@@ -1,5 +1,5 @@
 psycopg[binary]~=3.1.19
 testcontainers~=4.5.0
-requests<2.32.0  # `requests` renamed `get_connection` to `_get_connection`, which is a method docker-py monkeypatches. See https://github.com/docker/docker-py/issues/3256 Should be able to un-pin when docker-py hotfix is out.
+requests==2.32.2
 google~=3.0.0
 google.auth~=2.29.0
\ No newline at end of file
diff --git a/samples/python/sqlalchemy2-sample/requirements.txt b/samples/python/sqlalchemy2-sample/requirements.txt
index ab69bd17..696622fd 100644
--- a/samples/python/sqlalchemy2-sample/requirements.txt
+++ b/samples/python/sqlalchemy2-sample/requirements.txt
@@ -4,4 +4,4 @@ sqlalchemy==2.0.27
 google~=3.0.0
 google.auth~=2.29.0
 testcontainers~=4.5.0
-requests<2.32.0  # `requests` renamed `get_connection` to `_get_connection`, which is a method docker-py monkeypatches. See https://github.com/docker/docker-py/issues/3256 Should be able to un-pin when docker-py hotfix is out.
+requests==2.32.2
diff --git a/src/main/java/com/google/cloud/spanner/pgadapter/ConnectionHandler.java b/src/main/java/com/google/cloud/spanner/pgadapter/ConnectionHandler.java
index 932e2169..aab09343 100644
--- a/src/main/java/com/google/cloud/spanner/pgadapter/ConnectionHandler.java
+++ b/src/main/java/com/google/cloud/spanner/pgadapter/ConnectionHandler.java
@@ -665,7 +665,8 @@ public class ConnectionHandler implements Runnable {
   public IntermediatePreparedStatement getStatement(String statementName) {
     if (!hasStatement(statementName)) {
       throw PGExceptionFactory.newPGException(
-          "prepared statement " + statementName + " does not exist");
+          "prepared statement " + statementName + " does not exist",
+          SQLState.InvalidSqlStatementName);
     }
     return this.statementsMap.get(statementName);
   }
diff --git a/src/main/java/com/google/cloud/spanner/pgadapter/error/SQLState.java b/src/main/java/com/google/cloud/spanner/pgadapter/error/SQLState.java
index 724cd1fb..b2afd47e 100644
--- a/src/main/java/com/google/cloud/spanner/pgadapter/error/SQLState.java
+++ b/src/main/java/com/google/cloud/spanner/pgadapter/error/SQLState.java
@@ -158,6 +158,9 @@ public enum SQLState {
   InFailedSqlTransaction("25P02"),
   IdleInTransactionSessionTimeout("25P03"),
 
+  // Class 26 - Invalid SQL statement name
+  InvalidSqlStatementName("26000"),
+
   // Class 34 - Cursor
   InvalidCursorName("34000"),
 
diff --git a/src/main/java/com/google/cloud/spanner/pgadapter/statements/DiscardStatement.java b/src/main/java/com/google/cloud/spanner/pgadapter/statements/DiscardStatement.java
new file mode 100644
index 00000000..09b1d9ab
--- /dev/null
+++ b/src/main/java/com/google/cloud/spanner/pgadapter/statements/DiscardStatement.java
@@ -0,0 +1,152 @@
+// Copyright 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.cloud.spanner.pgadapter.statements;
+
+import com.google.cloud.spanner.Statement;
+import com.google.cloud.spanner.connection.AbstractStatementParser.ParsedStatement;
+import com.google.cloud.spanner.connection.AbstractStatementParser.StatementType;
+import com.google.cloud.spanner.connection.StatementResult;
+import com.google.cloud.spanner.pgadapter.ConnectionHandler;
+import com.google.cloud.spanner.pgadapter.error.PGExceptionFactory;
+import com.google.cloud.spanner.pgadapter.error.SQLState;
+import com.google.cloud.spanner.pgadapter.metadata.OptionsMetadata;
+import com.google.cloud.spanner.pgadapter.statements.BackendConnection.ConnectionState;
+import com.google.cloud.spanner.pgadapter.statements.BackendConnection.NoResult;
+import com.google.cloud.spanner.pgadapter.statements.DiscardStatement.ParsedDiscardStatement.DiscardType;
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableList;
+import com.google.common.util.concurrent.Futures;
+import java.util.List;
+import java.util.concurrent.Future;
+
+public class DiscardStatement extends IntermediatePortalStatement {
+  static final class ParsedDiscardStatement {
+    enum DiscardType {
+      PLANS,
+      SEQUENCES,
+      TEMPORARY,
+      ALL,
+    }
+
+    final DiscardType type;
+
+    private ParsedDiscardStatement(DiscardType type) {
+      this.type = type;
+    }
+  }
+
+  private final ParsedDiscardStatement discardStatement;
+
+  public DiscardStatement(
+      ConnectionHandler connectionHandler,
+      OptionsMetadata options,
+      String name,
+      ParsedStatement parsedStatement,
+      Statement originalStatement) {
+    super(
+        name,
+        new IntermediatePreparedStatement(
+            connectionHandler,
+            options,
+            name,
+            NO_PARAMETER_TYPES,
+            parsedStatement,
+            originalStatement),
+        NO_PARAMS,
+        ImmutableList.of(),
+        ImmutableList.of());
+    this.discardStatement = parse(originalStatement.getSql());
+  }
+
+  @Override
+  public String getCommandTag() {
+    return "DISCARD";
+  }
+
+  @Override
+  public StatementType getStatementType() {
+    return StatementType.CLIENT_SIDE;
+  }
+
+  @Override
+  public void executeAsync(BackendConnection backendConnection) {
+    this.executed = true;
+    try {
+      switch (discardStatement.type) {
+        case ALL:
+          if (backendConnection.getConnectionState() == ConnectionState.TRANSACTION) {
+            setFutureStatementResult(
+                Futures.immediateFailedFuture(
+                    PGExceptionFactory.newPGException(
+                        "DISCARD ALL cannot run inside a transaction block",
+                        SQLState.ActiveSqlTransaction)));
+            return;
+          }
+          connectionHandler.closeAllStatements();
+          break;
+        case PLANS:
+        case SEQUENCES:
+        case TEMPORARY:
+        default:
+          // The default is no-op as PGAdapter does not support clearing plans, sequences or
+          // temporary tables.
+      }
+    } catch (Exception exception) {
+      setFutureStatementResult(Futures.immediateFailedFuture(exception));
+      return;
+    }
+    setFutureStatementResult(Futures.immediateFuture(new NoResult()));
+  }
+
+  @Override
+  public Future<StatementResult> describeAsync(BackendConnection backendConnection) {
+    // Return null to indicate that this DISCARD statement does not return any
+    // RowDescriptionResponse.
+    return Futures.immediateFuture(null);
+  }
+
+  @Override
+  public IntermediatePortalStatement createPortal(
+      String name,
+      byte[][] parameters,
+      List<Short> parameterFormatCodes,
+      List<Short> resultFormatCodes) {
+    // DISCARD does not support binding any parameters, so we just return the same statement.
+    return this;
+  }
+
+  static ParsedDiscardStatement parse(String sql) {
+    Preconditions.checkNotNull(sql);
+
+    SimpleParser parser = new SimpleParser(sql);
+    if (!parser.eatKeyword("discard")) {
+      throw PGExceptionFactory.newPGException("not a valid DISCARD statement: " + sql);
+    }
+    DiscardType type;
+    if (parser.eatKeyword("all")) {
+      type = DiscardType.ALL;
+    } else if (parser.eatKeyword("plans")) {
+      type = DiscardType.PLANS;
+    } else if (parser.eatKeyword("sequences")) {
+      type = DiscardType.SEQUENCES;
+    } else if (parser.eatKeyword("temp") || parser.eatKeyword("temporary")) {
+      type = DiscardType.TEMPORARY;
+    } else {
+      throw PGExceptionFactory.newPGException("Invalid DISCARD statement: " + parser.getSql());
+    }
+    parser.throwIfHasMoreTokens();
+    return new ParsedDiscardStatement(type);
+  }
+}
diff --git a/src/main/java/com/google/cloud/spanner/pgadapter/wireprotocol/ParseMessage.java b/src/main/java/com/google/cloud/spanner/pgadapter/wireprotocol/ParseMessage.java
index a10a767a..b01fc53f 100644
--- a/src/main/java/com/google/cloud/spanner/pgadapter/wireprotocol/ParseMessage.java
+++ b/src/main/java/com/google/cloud/spanner/pgadapter/wireprotocol/ParseMessage.java
@@ -19,6 +19,7 @@ import static com.google.cloud.spanner.pgadapter.wireprotocol.QueryMessage.CLOSE
 import static com.google.cloud.spanner.pgadapter.wireprotocol.QueryMessage.COPY;
 import static com.google.cloud.spanner.pgadapter.wireprotocol.QueryMessage.DEALLOCATE;
 import static com.google.cloud.spanner.pgadapter.wireprotocol.QueryMessage.DECLARE;
+import static com.google.cloud.spanner.pgadapter.wireprotocol.QueryMessage.DISCARD;
 import static com.google.cloud.spanner.pgadapter.wireprotocol.QueryMessage.EXECUTE;
 import static com.google.cloud.spanner.pgadapter.wireprotocol.QueryMessage.FETCH;
 import static com.google.cloud.spanner.pgadapter.wireprotocol.QueryMessage.MOVE;
@@ -44,6 +45,7 @@ import com.google.cloud.spanner.pgadapter.statements.CloseStatement;
 import com.google.cloud.spanner.pgadapter.statements.CopyStatement;
 import com.google.cloud.spanner.pgadapter.statements.DeallocateStatement;
 import com.google.cloud.spanner.pgadapter.statements.DeclareStatement;
+import com.google.cloud.spanner.pgadapter.statements.DiscardStatement;
 import com.google.cloud.spanner.pgadapter.statements.ExecuteStatement;
 import com.google.cloud.spanner.pgadapter.statements.FetchStatement;
 import com.google.cloud.spanner.pgadapter.statements.IntermediatePreparedStatement;
@@ -148,6 +150,13 @@ public class ParseMessage extends AbstractQueryProtocolMessage {
             name,
             parsedStatement,
             originalStatement);
+      } else if (isCommand(DISCARD, originalStatement.getSql())) {
+        return new DiscardStatement(
+            connectionHandler,
+            connectionHandler.getServer().getOptions(),
+            name,
+            parsedStatement,
+            originalStatement);
       } else if (isCommand(DECLARE, originalStatement.getSql())) {
         return new DeclareStatement(
             connectionHandler,
diff --git a/src/main/java/com/google/cloud/spanner/pgadapter/wireprotocol/QueryMessage.java b/src/main/java/com/google/cloud/spanner/pgadapter/wireprotocol/QueryMessage.java
index 454288a5..61135469 100644
--- a/src/main/java/com/google/cloud/spanner/pgadapter/wireprotocol/QueryMessage.java
+++ b/src/main/java/com/google/cloud/spanner/pgadapter/wireprotocol/QueryMessage.java
@@ -29,6 +29,7 @@ public class QueryMessage extends ControlMessage {
   public static final String PREPARE = "PREPARE";
   public static final String EXECUTE = "EXECUTE";
   public static final String DEALLOCATE = "DEALLOCATE";
+  public static final String DISCARD = "DISCARD";
   public static final String VACUUM = "VACUUM";
   public static final String TRUNCATE = "TRUNCATE";
   public static final String SAVEPOINT = "SAVEPOINT";


Test patch:
diff --git a/src/test/java/com/google/cloud/spanner/pgadapter/JdbcSimpleModeMockServerTest.java b/src/test/java/com/google/cloud/spanner/pgadapter/JdbcSimpleModeMockServerTest.java
index fe173f6e..f1620f7e 100644
--- a/src/test/java/com/google/cloud/spanner/pgadapter/JdbcSimpleModeMockServerTest.java
+++ b/src/test/java/com/google/cloud/spanner/pgadapter/JdbcSimpleModeMockServerTest.java
@@ -16,12 +16,14 @@ package com.google.cloud.spanner.pgadapter;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 
 import com.google.cloud.spanner.Dialect;
 import com.google.cloud.spanner.MockSpannerServiceImpl.StatementResult;
 import com.google.cloud.spanner.SpannerException;
+import com.google.cloud.spanner.pgadapter.error.SQLState;
 import com.google.cloud.spanner.pgadapter.metadata.OptionsMetadata;
 import com.google.common.collect.ImmutableList;
 import com.google.protobuf.ListValue;
@@ -54,6 +56,7 @@ import org.junit.runners.Parameterized;
 import org.junit.runners.Parameterized.Parameter;
 import org.junit.runners.Parameterized.Parameters;
 import org.postgresql.jdbc.TimestampUtils;
+import org.postgresql.util.PSQLException;
 
 /**
  * Tests the native PG JDBC driver in simple query mode. This is similar to the protocol that is
@@ -571,6 +574,41 @@ public class JdbcSimpleModeMockServerTest extends AbstractMockServerTest {
     }
   }
 
+  @Test
+  public void testDiscard() throws SQLException {
+    try (Connection connection = DriverManager.getConnection(createUrl())) {
+      connection.setAutoCommit(true);
+      // Verify that all variants are supported.
+      connection.createStatement().execute("discard all");
+      connection.createStatement().execute("discard plans");
+      connection.createStatement().execute("discard sequences");
+      connection.createStatement().execute("discard temp");
+      connection.createStatement().execute("discard temporary");
+
+      // Create a prepared statement verify that it is dropped by DISCARD ALL.
+      connection.createStatement().execute("prepare foo as SELECT 1");
+      connection.createStatement().execute("execute foo");
+      connection.createStatement().execute("discard all");
+      PSQLException exception =
+          assertThrows(
+              PSQLException.class, () -> connection.createStatement().execute("execute foo"));
+      assertNotNull(exception.getServerErrorMessage());
+      assertEquals(
+          SQLState.InvalidSqlStatementName.toString(),
+          exception.getServerErrorMessage().getSQLState());
+
+      // Verify that 'discard all' is not accepted in a transaction block.
+      connection.setAutoCommit(false);
+      exception =
+          assertThrows(
+              PSQLException.class, () -> connection.createStatement().execute("discard all"));
+      assertNotNull(exception.getServerErrorMessage());
+      assertEquals(
+          SQLState.ActiveSqlTransaction.toString(),
+          exception.getServerErrorMessage().getSQLState());
+    }
+  }
+
   @Test
   public void testGetTimezoneStringUtc() throws SQLException {
     String sql = "select '2022-01-01 10:00:00+01'::timestamptz";
diff --git a/src/test/java/com/google/cloud/spanner/pgadapter/PgAdapterTestEnv.java b/src/test/java/com/google/cloud/spanner/pgadapter/PgAdapterTestEnv.java
index 9d3281de..087a61ed 100644
--- a/src/test/java/com/google/cloud/spanner/pgadapter/PgAdapterTestEnv.java
+++ b/src/test/java/com/google/cloud/spanner/pgadapter/PgAdapterTestEnv.java
@@ -50,6 +50,8 @@ import java.io.FileInputStream;
 import java.io.IOException;
 import java.net.URL;
 import java.nio.ByteBuffer;
+import java.time.Duration;
+import java.time.Instant;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -58,6 +60,7 @@ import java.util.Map;
 import java.util.UUID;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -67,6 +70,7 @@ public class PgAdapterTestEnv {
   private static final int INIT_PROTOCOL = 80877103;
   private static final int OPTIONS_PROTOCOL = 196608;
   private static final String CHANNEL_PROVIDER_PROPERTY = "CHANNEL_PROVIDER";
+  private static final AtomicBoolean DELETED_STALE_DATABASES = new AtomicBoolean();
 
   // GCP credentials file should be set through the 'GOOGLE_APPLICATION_CREDENTIALS' environment
   // variable.
@@ -189,6 +193,26 @@ public class PgAdapterTestEnv {
     spannerHost = getSpannerUrl();
     logger.info("Using Spanner host: " + spannerHost);
     options = createSpannerOptions();
+    deleteStaleTestDatabases();
+  }
+
+  private void deleteStaleTestDatabases() {
+    if (isDropStaleTestDatabases() && DELETED_STALE_DATABASES.compareAndSet(false, true)) {
+      DatabaseAdminClient client = getSpanner().getDatabaseAdminClient();
+      long thresholdTime = Instant.now().getEpochSecond() - Duration.ofHours(6L).getSeconds();
+      for (Database database : client.listDatabases(getInstanceId()).iterateAll()) {
+        if ((database.getId().getDatabase().startsWith("testdb_")
+                || database.getId().getDatabase().startsWith(getDatabaseId()))
+            && database.getCreateTime().getSeconds() <= thresholdTime) {
+          logger.info("Dropping stale test database " + database.getId().getName());
+          database.drop();
+        }
+      }
+    }
+  }
+
+  private boolean isDropStaleTestDatabases() {
+    return Boolean.parseBoolean(System.getenv("PG_ADAPTER_DROP_STALE_DATABASES"));
   }
 
   public void startPGAdapterServer(Iterable<String> additionalPGAdapterOptions) {
diff --git a/src/test/java/com/google/cloud/spanner/pgadapter/statements/DiscardStatementTest.java b/src/test/java/com/google/cloud/spanner/pgadapter/statements/DiscardStatementTest.java
new file mode 100644
index 00000000..331c61c4
--- /dev/null
+++ b/src/test/java/com/google/cloud/spanner/pgadapter/statements/DiscardStatementTest.java
@@ -0,0 +1,44 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.cloud.spanner.pgadapter.statements;
+
+import static com.google.cloud.spanner.pgadapter.statements.DiscardStatement.parse;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+
+import com.google.cloud.spanner.pgadapter.error.PGException;
+import com.google.cloud.spanner.pgadapter.statements.DiscardStatement.ParsedDiscardStatement.DiscardType;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class DiscardStatementTest {
+
+  @Test
+  public void testParse() {
+    assertEquals(DiscardType.ALL, parse("discard all").type);
+    assertEquals(DiscardType.PLANS, parse("discard plans").type);
+    assertEquals(DiscardType.SEQUENCES, parse("discard sequences").type);
+    assertEquals(DiscardType.TEMPORARY, parse("discard temp").type);
+    assertEquals(DiscardType.TEMPORARY, parse("discard temporary").type);
+    assertEquals(DiscardType.TEMPORARY, parse("discard/*comment*/temporary").type);
+
+    assertThrows(PGException.class, () -> parse("discard foo"));
+    assertThrows(PGException.class, () -> parse("discard"));
+    assertThrows(PGException.class, () -> parse("deallocate all foo"));
+    assertThrows(PGException.class, () -> parse("discard temp all"));
+  }
+}