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A universal transaction manager that achieves database-agnostic transactions and distributed transactions that span multiple databases

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package com.scalar.database.storage.cassandra;

import static com.datastax.driver.core.querybuilder.QueryBuilder.bindMarker;
import static com.datastax.driver.core.querybuilder.QueryBuilder.set;

import com.datastax.driver.core.BoundStatement;
import com.datastax.driver.core.PreparedStatement;
import com.datastax.driver.core.ResultSet;
import com.datastax.driver.core.Session;
import com.datastax.driver.core.querybuilder.QueryBuilder;
import com.datastax.driver.core.querybuilder.Update;
import com.scalar.database.api.Operation;
import com.scalar.database.api.Put;
import javax.annotation.Nonnull;
import javax.annotation.concurrent.ThreadSafe;

/**
 * A handler class for update statement
 *
 * @author Hiroyuki Yamada
 */
@ThreadSafe
public class UpdateStatementHandler extends MutateStatementHandler {

  /**
   * Constructs {@code UpdateStatementHandler} with the specified {@code Session}
   *
   * @param session session to be used with this statement
   */
  public UpdateStatementHandler(Session session) {
    super(session);
  }

  @Override
  @Nonnull
  protected PreparedStatement prepare(Operation operation) {
    checkArgument(operation, Put.class);

    Put put = (Put) operation;
    Update update = prepare(put);
    String query = update.getQueryString();

    return prepare(query);
  }

  @Override
  @Nonnull
  protected BoundStatement bind(PreparedStatement prepared, Operation operation) {
    checkArgument(operation, Put.class);

    BoundStatement bound = prepared.bind();
    bound = bind(bound, (Put) operation);

    return bound;
  }

  @Override
  @Nonnull
  protected ResultSet execute(BoundStatement bound, Operation operation) {
    return session.execute(bound);
  }

  private Update prepare(Put put) {
    Update update = QueryBuilder.update(put.forNamespace().get(), put.forTable().get());

    Update.Assignments assignments = update.with();
    put.getValues().forEach((k, v) -> assignments.and(set(k, bindMarker())));
    Update.Where where = update.where();
    put.getPartitionKey().forEach(v -> where.and(QueryBuilder.eq(v.getName(), bindMarker())));
    put.getClusteringKey()
        .ifPresent(
            k -> {
              k.forEach(v -> where.and(QueryBuilder.eq(v.getName(), bindMarker())));
            });

    setCondition(where, put);

    return update;
  }

  private BoundStatement bind(BoundStatement bound, Put put) {
    ValueBinder binder = new ValueBinder(bound);

    // bind from the front in the statement
    put.getValues().forEach((k, v) -> v.accept(binder));
    put.getPartitionKey().forEach(v -> v.accept(binder));
    put.getClusteringKey().ifPresent(k -> k.forEach(v -> v.accept(binder)));

    bindCondition(binder, put);

    return bound;
  }
}