add druid jdbc handler config for minimum number of rows per frame

docs/configuration/index.md

@@ -1644,7 +1644,8 @@ The Druid SQL server is configured through the following properties on the Broke
 |`druid.sql.enable`|Whether to enable SQL at all, including background metadata fetching. If false, this overrides all other SQL-related properties and disables SQL metadata, serving, and planning completely.|true|
 |`druid.sql.avatica.enable`|Whether to enable JDBC querying at `/druid/v2/sql/avatica/`.|true|
 |`druid.sql.avatica.maxConnections`|Maximum number of open connections for the Avatica server. These are not HTTP connections, but are logical client connections that may span multiple HTTP connections.|25|
-|`druid.sql.avatica.maxRowsPerFrame`|Maximum number of rows to return in a single JDBC frame. Setting this property to -1 indicates that no row limit should be applied. Clients can optionally specify a row limit in their requests; if a client specifies a row limit, the lesser value of the client-provided limit and `maxRowsPerFrame` will be used.|5,000|
+|`druid.sql.avatica.maxRowsPerFrame`|Maximum acceptable value for the JDBC client `Statement.setFetchSize` method. This setting determines the maximum number of rows that Druid will populate in a single 'fetch' for a JDBC `ResultSet`. Set this property to -1 to enforce no row limit on the server-side and potentially return the entire set of rows on the initial statement execution. If the JDBC client calls `Statement.setFetchSize` with a value other than -1, Druid uses the lesser value of the client-provided limit and `maxRowsPerFrame`. If `maxRowsPerFrame` is smaller than `minRowsPerFrame`, then the `ResultSet` size will be fixed. To handle queries that produce results with a large number of rows, you can increase value of `druid.sql.avatica.maxRowsPerFrame` to reduce the number of fetches required to completely transfer the result set.|5,000|
+|`druid.sql.avatica.minRowsPerFrame`|Minimum acceptable value for the JDBC client `Statement.setFetchSize` method. The value for this property must greater than 0. If the JDBC client calls `Statement.setFetchSize` with a lesser value, Druid uses `minRowsPerFrame` instead. If `maxRowsPerFrame` is less than `minRowsPerFrame`, Druid uses the minimum value of the two. For handling queries which produce results with a large number of rows, you can increase this value to reduce the number of fetches required to completely transfer the result set.|100|
 |`druid.sql.avatica.maxStatementsPerConnection`|Maximum number of simultaneous open statements per Avatica client connection.|4|
 |`druid.sql.avatica.connectionIdleTimeout`|Avatica client connection idle timeout.|PT5M|
 |`druid.sql.http.enable`|Whether to enable JSON over HTTP querying at `/druid/v2/sql/`.|true|

sql/src/main/java/org/apache/druid/sql/avatica/AvaticaServerConfig.java

@@ -20,21 +20,31 @@
 package org.apache.druid.sql.avatica;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import com.google.common.base.Preconditions;
 import org.joda.time.Period;
 
 class AvaticaServerConfig
 {
+  public static int DEFAULT_MAX_CONNECTIONS = 25;
+  public static int DEFAULT_MAX_STATEMENTS_PER_CONNECTION = 4;
+  public static Period DEFAULT_CONNECTION_IDLE_TIMEOUT = new Period("PT5M");
+  public static int DEFAULT_MIN_ROWS_PER_FRAME = 100;
+  public static int DEFAULT_MAX_ROWS_PER_FRAME = 5000;
+
+  @JsonProperty
+  public int maxConnections = DEFAULT_MAX_CONNECTIONS;
+
   @JsonProperty
-  public int maxConnections = 25;
+  public int maxStatementsPerConnection = DEFAULT_MAX_STATEMENTS_PER_CONNECTION;
 
   @JsonProperty
-  public int maxStatementsPerConnection = 4;
+  public Period connectionIdleTimeout = DEFAULT_CONNECTION_IDLE_TIMEOUT;
 
   @JsonProperty
-  public Period connectionIdleTimeout = new Period("PT5M");
+  public int minRowsPerFrame = DEFAULT_MIN_ROWS_PER_FRAME;
 
   @JsonProperty
-  public int maxRowsPerFrame = 5000;
+  public int maxRowsPerFrame = DEFAULT_MAX_ROWS_PER_FRAME;
 
   public int getMaxConnections()
   {
@@ -55,4 +65,16 @@ public int getMaxRowsPerFrame()
   {
     return maxRowsPerFrame;
   }
+
+  public int getMinRowsPerFrame()
+  {
+    Preconditions.checkArgument(
+        minRowsPerFrame > 0,
+        "'druid.sql.avatica.minRowsPerFrame' must be set to a value greater than 0"
+    );
+    if (maxRowsPerFrame > 0) {
+      return Math.min(getMaxRowsPerFrame(), minRowsPerFrame);
+    }
+    return minRowsPerFrame;
+  }
 }

sql/src/main/java/org/apache/druid/sql/avatica/DruidMeta.java

@@ -627,17 +627,40 @@ private MetaResultSet sqlResultSet(final ConnectionHandle ch, final String sql)
     }
   }
 
+  /**
+   * Determine JDBC 'frame' size, that is the number of results which will be returned to a single
+   * {@link java.sql.ResultSet}. This value corresponds to {@link java.sql.Statement#setFetchSize(int)} (which is a user
+   * hint, we don't have to honor it), and this method modifies it, ensuring the actual chosen value falls within
+   * {@link AvaticaServerConfig#minRowsPerFrame} and {@link AvaticaServerConfig#maxRowsPerFrame}.
+   *
+   * A value of -1 supplied as input indicates that the client has no preference for fetch size, and can handle
+   * unlimited results (at our discretion). Similarly, a value of -1 for {@link AvaticaServerConfig#maxRowsPerFrame}
+   * also indicates that there is no upper limit on fetch size on the server side.
+   *
+   * {@link AvaticaServerConfig#minRowsPerFrame} must be configured to a value greater than 0, because it will be
+   * checked against if any additional frames are required (which means one of the input or maximum was set to a value
+   * other than -1).
+   */
   private int getEffectiveMaxRowsPerFrame(int clientMaxRowsPerFrame)
   {
     // no configured row limit, use the client provided limit
     if (config.getMaxRowsPerFrame() < 0) {
-      return clientMaxRowsPerFrame;
+      return adjustForMinumumRowsPerFrame(clientMaxRowsPerFrame);
     }
     // client provided no row limit, use the configured row limit
     if (clientMaxRowsPerFrame < 0) {
-      return config.getMaxRowsPerFrame();
+      return adjustForMinumumRowsPerFrame(config.getMaxRowsPerFrame());
     }
-    return Math.min(clientMaxRowsPerFrame, config.getMaxRowsPerFrame());
+    return adjustForMinumumRowsPerFrame(Math.min(clientMaxRowsPerFrame, config.getMaxRowsPerFrame()));
+  }
+
+  /**
+   * coerce fetch size to be, at minimum, {@link AvaticaServerConfig#minRowsPerFrame}
+   */
+  private int adjustForMinumumRowsPerFrame(int rowsPerFrame)
+  {
+    final int adjustedRowsPerFrame = Math.max(config.getMinRowsPerFrame(), rowsPerFrame);
+    return adjustedRowsPerFrame;
   }
 
   private static String withEscapeClause(String toEscape)

sql/src/test/java/org/apache/druid/sql/avatica/AvaticaModuleTest.java

@@ -24,6 +24,8 @@
 import com.google.inject.Key;
 import com.google.inject.Scopes;
 import com.google.inject.TypeLiteral;
+import org.apache.druid.guice.JsonConfigProvider;
+import org.apache.druid.guice.JsonConfigurator;
 import org.apache.druid.guice.LazySingleton;
 import org.apache.druid.guice.annotations.Self;
 import org.apache.druid.jackson.JacksonModule;
@@ -35,11 +37,14 @@
 import org.eclipse.jetty.server.Handler;
 import org.junit.Assert;
 import org.junit.Before;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 import org.junit.runner.RunWith;
 
 import javax.validation.Validation;
 import javax.validation.Validator;
+import java.util.Properties;
 import java.util.Set;
 
 @RunWith(EasyMockRunner.class)
@@ -52,6 +57,9 @@ public class AvaticaModuleTest
   @Mock
   private DruidMeta druidMeta;
 
+  @Rule
+  public ExpectedException expectedException = ExpectedException.none();
+
   private AvaticaModule target;
   private Injector injector;
 
@@ -95,6 +103,76 @@ public void testAvaticaServerConfigIsInjectable()
   {
     AvaticaServerConfig config = injector.getInstance(AvaticaServerConfig.class);
     Assert.assertNotNull(config);
+    Assert.assertEquals(AvaticaServerConfig.DEFAULT_MAX_CONNECTIONS, config.getMaxConnections());
+    Assert.assertEquals(
+        AvaticaServerConfig.DEFAULT_MAX_STATEMENTS_PER_CONNECTION,
+        config.getMaxStatementsPerConnection()
+    );
+    Assert.assertEquals(AvaticaServerConfig.DEFAULT_CONNECTION_IDLE_TIMEOUT, config.getConnectionIdleTimeout());
+    Assert.assertEquals(AvaticaServerConfig.DEFAULT_MIN_ROWS_PER_FRAME, config.getMinRowsPerFrame());
+    Assert.assertEquals(AvaticaServerConfig.DEFAULT_MAX_ROWS_PER_FRAME, config.getMaxRowsPerFrame());
+  }
+
+  @Test
+  public void testAvaticaServerConfigProperties()
+  {
+    Properties properties = new Properties();
+    final JsonConfigProvider<AvaticaServerConfig> provider = JsonConfigProvider.of(
+        "druid.sql.avatica",
+        AvaticaServerConfig.class
+    );
+    properties.setProperty("druid.sql.avatica.maxRowsPerFrame", "50000");
+    properties.setProperty("druid.sql.avatica.minRowsPerFrame", "10000");
+    provider.inject(properties, injector.getInstance(JsonConfigurator.class));
+    final AvaticaServerConfig config = provider.get().get();
+    Assert.assertNotNull(config);
+    Assert.assertEquals(AvaticaServerConfig.DEFAULT_MAX_CONNECTIONS, config.getMaxConnections());
+    Assert.assertEquals(
+        AvaticaServerConfig.DEFAULT_MAX_STATEMENTS_PER_CONNECTION,
+        config.getMaxStatementsPerConnection()
+    );
+    Assert.assertEquals(AvaticaServerConfig.DEFAULT_CONNECTION_IDLE_TIMEOUT, config.getConnectionIdleTimeout());
+    Assert.assertEquals(10_000, config.getMinRowsPerFrame());
+    Assert.assertEquals(50_000, config.getMaxRowsPerFrame());
+  }
+
+  @Test
+  public void testAvaticaServerConfigPropertiesSmallerMaxIsAlsoMin()
+  {
+    Properties properties = new Properties();
+    final JsonConfigProvider<AvaticaServerConfig> provider = JsonConfigProvider.of(
+        "druid.sql.avatica",
+        AvaticaServerConfig.class
+    );
+    properties.setProperty("druid.sql.avatica.maxRowsPerFrame", "50");
+    provider.inject(properties, injector.getInstance(JsonConfigurator.class));
+    final AvaticaServerConfig config = provider.get().get();
+    Assert.assertNotNull(config);
+    Assert.assertEquals(AvaticaServerConfig.DEFAULT_MAX_CONNECTIONS, config.getMaxConnections());
+    Assert.assertEquals(
+        AvaticaServerConfig.DEFAULT_MAX_STATEMENTS_PER_CONNECTION,
+        config.getMaxStatementsPerConnection()
+    );
+    Assert.assertEquals(AvaticaServerConfig.DEFAULT_CONNECTION_IDLE_TIMEOUT, config.getConnectionIdleTimeout());
+    Assert.assertEquals(50, config.getMinRowsPerFrame());
+    Assert.assertEquals(50, config.getMaxRowsPerFrame());
+  }
+
+  @Test
+  public void testAvaticaServerConfigPropertiesBadMinRowsPerFrame()
+  {
+    expectedException.expect(IllegalArgumentException.class);
+    expectedException.expectMessage("'druid.sql.avatica.minRowsPerFrame' must be set to a value greater than 0");
+    Properties properties = new Properties();
+    final JsonConfigProvider<AvaticaServerConfig> provider = JsonConfigProvider.of(
+        "druid.sql.avatica",
+        AvaticaServerConfig.class
+    );
+    properties.setProperty("druid.sql.avatica.minRowsPerFrame", "-1");
+    provider.inject(properties, injector.getInstance(JsonConfigurator.class));
+    final AvaticaServerConfig config = provider.get().get();
+    Assert.assertNotNull(config);
+    config.getMinRowsPerFrame();
   }
 
   @Test

sql/src/test/java/org/apache/druid/sql/avatica/DruidAvaticaHandlerTest.java

@@ -918,6 +918,107 @@ public Frame fetch(
     );
   }
 
+
+  @Test
+  public void testMinRowsPerFrame() throws Exception
+  {
+    final int minFetchSize = 1000;
+    final AvaticaServerConfig smallFrameConfig = new AvaticaServerConfig()
+    {
+      @Override
+      public int getMaxConnections()
+      {
+        return 2;
+      }
+
+      @Override
+      public int getMaxStatementsPerConnection()
+      {
+        return 4;
+      }
+
+      @Override
+      public int getMinRowsPerFrame()
+      {
+        return minFetchSize;
+      }
+    };
+
+    final PlannerConfig plannerConfig = new PlannerConfig();
+    final DruidOperatorTable operatorTable = CalciteTests.createOperatorTable();
+    final ExprMacroTable macroTable = CalciteTests.createExprMacroTable();
+    final List<Meta.Frame> frames = new ArrayList<>();
+    SchemaPlus rootSchema =
+        CalciteTests.createMockRootSchema(conglomerate, walker, plannerConfig, AuthTestUtils.TEST_AUTHORIZER_MAPPER);
+    DruidMeta smallFrameDruidMeta = new DruidMeta(
+        CalciteTests.createSqlLifecycleFactory(
+            new PlannerFactory(
+                rootSchema,
+                CalciteTests.createMockQueryLifecycleFactory(walker, conglomerate),
+                operatorTable,
+                macroTable,
+                plannerConfig,
+                AuthTestUtils.TEST_AUTHORIZER_MAPPER,
+                CalciteTests.getJsonMapper(),
+                CalciteTests.DRUID_SCHEMA_NAME
+            )
+        ),
+        smallFrameConfig,
+        injector
+    )
+    {
+      @Override
+      public Frame fetch(
+          final StatementHandle statement,
+          final long offset,
+          final int fetchMaxRowCount
+      ) throws NoSuchStatementException, MissingResultsException
+      {
+        // overriding fetch allows us to track how many frames are processed after the first frame, and also fetch size
+        Assert.assertEquals(minFetchSize, fetchMaxRowCount);
+        Frame frame = super.fetch(statement, offset, fetchMaxRowCount);
+        frames.add(frame);
+        return frame;
+      }
+    };
+
+    final DruidAvaticaHandler handler = new DruidAvaticaHandler(
+        smallFrameDruidMeta,
+        new DruidNode("dummy", "dummy", false, 1, null, true, false),
+        new AvaticaMonitor()
+    );
+    final int port = ThreadLocalRandom.current().nextInt(9999) + 20000;
+    Server smallFrameServer = new Server(new InetSocketAddress("127.0.0.1", port));
+    smallFrameServer.setHandler(handler);
+    smallFrameServer.start();
+    String smallFrameUrl = StringUtils.format(
+        "jdbc:avatica:remote:url=http://127.0.0.1:%d%s",
+        port,
+        DruidAvaticaHandler.AVATICA_PATH
+    );
+    Connection smallFrameClient = DriverManager.getConnection(smallFrameUrl, "regularUser", "druid");
+
+    // use a prepared statement because avatica currently ignores fetchSize on the initial fetch of a Statement
+    PreparedStatement statement = smallFrameClient.prepareStatement("SELECT dim1 FROM druid.foo");
+    // set a fetch size below the minimum configured threshold
+    statement.setFetchSize(2);
+    final ResultSet resultSet = statement.executeQuery();
+    List<Map<String, Object>> rows = getRows(resultSet);
+    // expect minimum threshold to be used, which should be enough to do this all in first fetch
+    Assert.assertEquals(0, frames.size());
+    Assert.assertEquals(
+        ImmutableList.of(
+            ImmutableMap.of("dim1", ""),
+            ImmutableMap.of("dim1", "10.1"),
+            ImmutableMap.of("dim1", "2"),
+            ImmutableMap.of("dim1", "1"),
+            ImmutableMap.of("dim1", "def"),
+            ImmutableMap.of("dim1", "abc")
+        ),
+        rows
+    );
+  }
+
   @Test
   @SuppressWarnings("unchecked")
   public void testSqlRequestLog() throws Exception