introduce batch insert

src/main/java/com/jcabi/jdbc/JdbcSession.java

@@ -36,6 +36,7 @@
 import java.util.Collection;
 import java.util.LinkedList;
 import java.util.UUID;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
 import javax.sql.DataSource;
 import lombok.EqualsAndHashCode;
@@ -158,6 +159,8 @@ public final class JdbcSession {
      */
     private final transient Collection<Object> args;
 
+    private final transient AtomicInteger batchSize;
+
     /**
      * Arguments.
      *
@@ -196,11 +199,12 @@ public final class JdbcSession {
     @SuppressWarnings("PMD.ConstructorOnlyInitializesOrCallOtherConstructors")
     public JdbcSession(final DataSource src) {
         this.args = new LinkedList<>();
+        this.batchSize = new AtomicInteger(0);
         this.preparations = new LinkedList<>();
         this.connection = new AtomicReference<>();
         this.auto = true;
         this.source = src;
-        this.preparations.add(new PrepareArgs(this.args));
+        this.preparations.add(new PrepareArgs(this.args, this.batchSize));
     }
 
     /**
@@ -288,7 +292,8 @@ public JdbcSession clear() {
         synchronized (this.args) {
             this.args.clear();
             this.preparations.clear();
-            this.preparations.add(new PrepareArgs(this.args));
+            this.batchSize.set(0);
+            this.preparations.add(new PrepareArgs(this.args, this.batchSize));
         }
         return this;
     }
@@ -368,6 +373,16 @@ public <T> T update(final Outcome<T> outcome)
         );
     }
 
+    public <T> T batchInsert(final Outcome<T> outcome, int batchSize)
+            throws SQLException {
+        this.batchSize.set(batchSize);
+        return this.run(
+                outcome,
+                new Connect.WithKeys(this.query),
+                Request.EXECUTE_BATCH_UPDATE
+        );
+    }
+
     /**
      * Call an SQL stored procedure.
      *

src/main/java/com/jcabi/jdbc/PrepareArgs.java

@@ -35,6 +35,7 @@
 import java.sql.Types;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.concurrent.atomic.AtomicInteger;
 
 /**
  * Prepare arguments.
@@ -48,12 +49,15 @@ final class PrepareArgs implements Preparation {
      */
     private final transient Collection<Object> args;
 
+    private final AtomicInteger updateBatchSize;
+
     /**
      * Ctor.
      * @param arguments Arguments
      */
-    PrepareArgs(final Collection<Object> arguments) {
+    PrepareArgs(final Collection<Object> arguments, final AtomicInteger updateBatchSize) {
         this.args = Collections.unmodifiableCollection(arguments);
+        this.updateBatchSize = updateBatchSize;
     }
 
     @Override
@@ -64,8 +68,14 @@ final class PrepareArgs implements Preparation {
         }
     )
     public void prepare(final PreparedStatement stmt) throws SQLException {
-        int pos = 1;
+        int argNumber = 1;
         for (final Object arg : this.args) {
+            int pos;
+            if (this.updateBatchSize.get() != 0) {
+                pos = (argNumber - 1) % this.updateBatchSize.get() + 1;
+            } else {
+                pos = argNumber;
+            }
             if (arg == null) {
                 stmt.setNull(pos, Types.NULL);
             } else if (arg instanceof Long) {
@@ -85,7 +95,10 @@ public void prepare(final PreparedStatement stmt) throws SQLException {
             } else {
                 stmt.setObject(pos, arg);
             }
-            ++pos;
+            if (this.updateBatchSize.get() != 0 && argNumber % this.updateBatchSize.get() == 0) {
+                stmt.addBatch();
+            }
+            ++argNumber;
         }
     }
 }

src/main/java/com/jcabi/jdbc/Request.java

@@ -64,6 +64,18 @@ public ResultSet fetch(final PreparedStatement stmt)
         }
     };
 
+    /**
+     * Execute update.
+     */
+    Request EXECUTE_BATCH_UPDATE = new Request() {
+        @Override
+        public ResultSet fetch(final PreparedStatement stmt)
+                throws SQLException {
+            stmt.executeBatch();
+            return stmt.getGeneratedKeys();
+        }
+    };
+
     /**
      * Execute query.
      */

src/main/java/com/jcabi/jdbc/UpdateBatch.java

@@ -0,0 +1,4 @@
+package com.jcabi.jdbc;
+
+public interface UpdateBatch {
+}

src/test/java/com/jcabi/jdbc/JdbcSessionITCase.java → src/test/java/com/jcabi/jdbc/JdbcSessionITTest.java

@@ -51,7 +51,7 @@
  * @since 0.1
  */
 @Testcontainers(disabledWithoutDocker = true)
-final class JdbcSessionITCase {
+final class JdbcSessionITTest {
 
     /**
      * The database container.
@@ -60,6 +60,32 @@ final class JdbcSessionITCase {
     private final JdbcDatabaseContainer<?> container =
         new PostgreSQLContainer<>("postgres:9.6.12");
 
+    @Test
+    void batchInsert() throws Exception {
+        final DataSource source = this.source();
+        new JdbcSession(source)
+                .sql("CREATE TABLE IF NOT EXISTS transactions (type VARCHAR(4), amount INTEGER)")
+                .execute()
+                .sql("INSERT INTO transactions (type, amount) VALUES (?, ?)")
+                .set("buy").set(42)
+                .set("sell").set(5)
+                .set("sell").set(12)
+                .set("sell").set(345)
+                .set("buy").set(1)
+                .set("sell").set(324)
+                .set("buy").set(42)
+                .set("buy").set(8)
+                .batchInsert(Outcome.NOT_EMPTY, 2);
+        MatcherAssert.assertThat(
+                new JdbcSession(source)
+                        .sql("SELECT SUM(amount) FROM transactions")
+                        .select(new SingleOutcome<>(Long.class)),
+                Matchers.equalTo(
+                        42L + 5 + 12 + 345 + 1 + 324 + 42 + 8
+                )
+        );
+    }
+
     /**
      * JdbcSession can do PostgreSQL manipulations.
      *