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/*-------------------------------------------------------------------------
*
* Copyright (c) 2004-2014, PostgreSQL Global Development Group
* Copyright (c) 2004, Open Cloud Limited.
*
*
*-------------------------------------------------------------------------
*/
package org.postgresql.core;

import org.postgresql.PGNotification;
import org.postgresql.util.HostSpec;

import java.sql.*;
import java.util.Set;

/**
 * Provides access to protocol-level connection operations.
 *
 * @author Oliver Jowett ([email protected])
 */
public interface ProtocolConnection {
    /**
     * Constant returned by {@link #getTransactionState} indicating that no
     * transaction is currently open.
     */
    static final int TRANSACTION_IDLE = 0;

    /**
     * Constant returned by {@link #getTransactionState} indicating that a
     * transaction is currently open.
     */
    static final int TRANSACTION_OPEN = 1;

    /**
     * Constant returned by {@link #getTransactionState} indicating that a
     * transaction is currently open, but it has seen errors and will
     * refuse subsequent queries until a ROLLBACK.
     */
    static final int TRANSACTION_FAILED = 2;

    /**
     * @return the host and port this connection is connected to.
     */
    HostSpec getHostSpec();

    /**
     * @return the user this connection authenticated as.
     */
    String getUser();

    /**
     * @return the database this connection is connected to.
     */
    String getDatabase();

    /**
     * Return the server version from the server_version GUC.
     *
     * Note that there's no requirement for this to be numeric or of the form
     * x.y.z. PostgreSQL development releases usually have the format x.ydevel
     * e.g. 9.4devel; betas usually x.ybetan e.g.  9.4beta1. The
     * --with-extra-version configure option may add an arbitrary string to
     * this.
     *
     * Don't use this string for logic, only use it when displaying the server
     * version to the user. Prefer getServerVersionNum() for all logic
     * purposes.
     *
     * @return the server version string from the server_version guc
     */
    String getServerVersion();

    /**
     * Get a machine-readable server version.
     *
     * This returns the value of the server_version_num GUC. If no such GUC exists, 
     * it falls back on attempting to parse the text server version for the major version.
     * If there's no minor version (e.g. a devel or beta release) then the
     * minor version is set to zero. If the version could not be parsed, zero is returned.
     *
     * @return the server version in numeric XXYYZZ form, eg 090401, from server_version_num
     */
    int getServerVersionNum();

    /**
     * @return the current encoding in use by this connection
     */
    Encoding getEncoding();
    
    /**
     * Returns whether the server treats string-literals according to the SQL
     * standard or if it uses traditional PostgreSQL escaping rules. Versions
     * up to 8.1 always treated backslashes as escape characters in
     * string-literals. Since 8.2, this depends on the value of the
     * standard_conforming_strings server variable.
     * 
     * @return true if the server treats string literals according to the SQL
     *   standard
     */
    boolean getStandardConformingStrings();

    /**
     * Get the current transaction state of this connection.
     * 
     * @return a ProtocolConnection.TRANSACTION_* constant.
     */
    int getTransactionState();

    /**
     * Retrieve and clear the set of asynchronous notifications pending on this
     * connection.
     *
     * @return an array of notifications; if there are no notifications, an empty
     *   array is returned.
     */
    PGNotification[] getNotifications() throws SQLException;

    /**
     * Retrieve and clear the chain of warnings accumulated on this connection.
     *
     * @return the first SQLWarning in the chain; subsequent warnings can be
     *   found via SQLWarning.getNextWarning().
     */
    SQLWarning getWarnings();

    /**
     * @return the QueryExecutor instance for this connection.
     */
    QueryExecutor getQueryExecutor();

    /**
     * Sends a query cancellation for this connection.
     * @throws SQLException if something goes wrong.
     */
    void sendQueryCancel() throws SQLException;

    /**
     * Close this connection cleanly.
     */
    void close();

    /**
     * Check if this connection is closed.
     *
     * @return true iff the connection is closed.
     */
    boolean isClosed();
    
    /**
     * 
     * @return the version of the implementation
     */
    public int getProtocolVersion();

    /**
     * Sets the oids that should be received using binary encoding.
     *
     * @param useBinaryForOids The oids to request with binary encoding.
     */
    public void setBinaryReceiveOids(Set useBinaryForOids);

    /**
     * Returns true if server uses integer instead of double for binary
     * date and time encodings.
     * 
     * @return the server integer_datetime setting.
     */
    public boolean getIntegerDateTimes();

    /**
     * Return the process ID (PID) of the backend server process handling this connection.
     */
    public int getBackendPID();

    /**
     * Abort at network level without sending the Terminate message to the backend.
     */
    public void abort();
}