我正在尝试建立一个可以在我的笔记本电脑上运行的 flask 应用程序的Docker映像。这个应用程序用于使用Python生成PostgreSQL转储。所以我需要添加pg_dump和libpq.so.5。请参见下面我的Docker文件：

FROM XXX/postgres:13.9-alpine as postgres
FROM XXX/python:3.8-alpine

USER root

WORKDIR /dump_generator_api

COPY requirements.txt ./
RUN python3 -m pip install --upgrade pip
RUN pip3 install -r requirements.txt

COPY --from=postgres /usr/local/bin/pg_dump /usr/local/bin/pg_dump
COPY --from=postgres /usr/local/lib/libpq.so.5 /usr/local/lib/libpq.so.5

ADD . /dump_generator_api
EXPOSE 5000
CMD ["python", "/dump_generator_api/app.py"]

构建映像后，我尝试应用pg_dump命令（/usr/local/bin # pg_dump -U pgsqladmin -h XXX -p XXX XXX〉backup.sql），但出现以下错误，我不明白：

Error loading shared library libldap.so.2: No such file or directory (needed by /usr/local/lib/libpq.so.5)
Error relocating /usr/local/lib/libpq.so.5: ldap_err2string: symbol not found
Error relocating /usr/local/lib/libpq.so.5: ldap_result: symbol not found
Error relocating /usr/local/lib/libpq.so.5: ldap_simple_bind: symbol not found
Error relocating /usr/local/lib/libpq.so.5: ldap_count_entries: symbol not found
Error relocating /usr/local/lib/libpq.so.5: ldap_unbind: symbol not found
Error relocating /usr/local/lib/libpq.so.5: ldap_set_option: symbol not found
Error relocating /usr/local/lib/libpq.so.5: ldap_search_st: symbol not found
Error relocating /usr/local/lib/libpq.so.5: ldap_value_free_len: symbol not found
Error relocating /usr/local/lib/libpq.so.5: ldap_get_values_len: symbol not found
Error relocating /usr/local/lib/libpq.so.5: ldap_first_entry: symbol not found
Error relocating /usr/local/lib/libpq.so.5: ldap_init: symbol not found
Error relocating /usr/local/lib/libpq.so.5: ldap_msgfree: symbol not found

你知道我该怎么解决这个问题吗？我尝试了不同的Docker图像，同样的错误出现了。我不知道我应该在哪里以及如何添加这个libldap.so.2.