在psycopg2中執行SQL文件

Question

此功能或多或少是我們為技術支持人員提供的實用程序的一部分，旨在為他們提供一種從postgres備份中提取表，重命名表並將其重新插入另一個數據庫的簡便方法。 在使用cur.execute（）將表實際插入所選數據庫之前，我的函數可以正常工作。 sed（是的，我想堅持使用sed），提取部分的效果很好。 我想用psycopg2以某種方式執行該文件，但是如果有人有使用子進程和psql的想法，我願意接受其他建議。 通過表名列表，目標數據庫和sql文件備份調用此函數。 我看過其他使用.read（）的示例。 我也知道我應該將文件名轉換為變量以清理代碼。 如果可能，它還需要使用python 2.6。

for tbl in selected_tables:
    # Open a file each iteration, dump the table in to it. Use .wait() to make sure the command finishes.
    table_file = open(str(tbl) + backup_suffix + ".sql", "w")
    p1 = subprocess.Popen(["/usr/bin/pg_restore", backup_picked, "-t", tbl], stdout=table_file)
    p1.wait()

    # Rename every instance of the table in the restore file. Format: _backup_YYYYMMDD
    sed_guts = "s/" + str(tbl) + "/"  + str(tbl) + backup_suffix + "/g"
    p2 = subprocess.Popen(["/bin/sed", "-i", sed_guts, str(tbl) + backup_suffix + ".sql"])
    p2.wait()
    table_file.close()

    # Restore the tables.
    try:
        # Gets the proper connection information. Works fine.
        site_config = site.ParseConfig(target_site)

        contents = open(str(tbl) + backup_suffix + ".sql", "r")


        con = psycopg2.connect(user=site_config['dbusername'],host=site_config['host'], \
                            password= site_config['password'], port=site_config['port'],\
                            dbname=site_config['dbname'])

        con.set_isolation_level(psycopg2.extensions.ISOLATION_LEVEL_AUTOCOMMIT)

        # Connect to postgres or to the db and then execute the query.
        cur = con.cursor()
        # Fails here
        cur.execute(contents.read())
        os.remove(str(tbl) + backup_suffix + ".sql")

    except:
        os.remove(str(tbl) + backup_suffix + ".sql")

Answer 1

最后，我最終還是回到了psql和subprocess.Popen上，shell = True。 這不是我的首選方法，因為我還有其他限制，所以我願意走這條路。 如果有人好奇，這就是我所做的。

backup_suffix = site.FileSuffix(backup_picked)

# Do the actual restoration here. Use sed to rename every instance in the files that will be created below.
# Make sure the created files get removed before finishing.
for tbl in selected_tables:
    table_file_name = str(tbl) + backup_suffix + ".sql"

    # Open a file each iteration, dump the table in to it. Use .wait() to make sure the command finishes.
    table_file = open(table_file_name, "w")
    p1 = subprocess.Popen(["/usr/bin/pg_restore", backup_picked, "-t", tbl], stdout=table_file)
    p1.wait()
    table_file.close()

    # Rename every instance of the table in the restore file. Format: _backup_YYYYMMDD
    sed_guts = "s/" + str(tbl) + "/"  + str(tbl) + backup_suffix + "/g"
    p2 = subprocess.Popen(["/bin/sed", "-i", sed_guts, table_file_name])
    p2.wait()

    # Use psql to restore the tables.
    try:
        site_config = site.ParseConfig(target_site)
        dontuse, site_config = addFlags(site_config, site_config)

        command = '/usr/bin/psql %s %s %s %s < %s' % (site_config['host'], site_config['dbusername'],
                                                       site_config['dbname'], site_config['port'], table_file_name)

        p2 = subprocess.Popen('%s' % command, shell=True)
        p2.communicate()[0]

        os.remove(table_file_name)

    except:
        os.remove(table_file_name)
        session.CleanUp()

    exit(0)

還有多種方法可以在字符串中寫入多個變量。 如果有人好奇，這里有個幫助鏈接： 在Python中使用多個參數進行字符串格式化（例如'％s ...％s'）

這是另一個用於在Python中打開和關閉文件的好資源： http : //www.tutorialspoint.com/python/python_files_io.htm