记一次hive版本升级
之前的项目中hive版本用的是 apache-hive-1.2.2-bin，最近需要将hive版本升级到apache-hive-2.3.4-bin， 本来想着元数据在mysql中，直接部署好hive启动就好了，
结果提示元数据未初始化，查找一下资料，发现不同版本hive的元数据信息有所不同，而官方也给了升级方法，这里记录一下。
首先，找到我们要升级的hive，找到apache-hive-2.3.4-bin/scripts/metastore/upgrade/mysql 这个目录
这个目录下有一个README，里面讲了如何升级
Hive MetaStore Upgrade HowTo
============================
This document describes how to upgrade the schema of a MySQL backed
Hive MetaStore instance from one release version of Hive to another
release version of Hive. For example, by following the steps listed
below it is possible to upgrade a Hive 0.5.0 MetaStore schema to a
Hive 0.7.0 MetaStore schema. Before attempting this project we
strongly recommend that you read through all of the steps in this
document and familiarize yourself with the required tools.
MetaStore Upgrade Steps
=======================
1) Shutdown your MetaStore instance and restrict access to the
MetaStore's MySQL database. It is very important that no one else
accesses or modifies the contents of database while you are
performing the schema upgrade.
2) Create a backup of your MySQL metastore database. This will allow
you to revert any changes made during the upgrade process if
something goes wrong. The mysqldump utility is the easiest way to
create a backup of a MySQL database:
% mysqldump --opt <metastore_db_name> > metastore_backup.sql
Note that you may need also need to specify a hostname and username
using the --host and --user command line switches.
3) Dump your metastore database schema to a file. We use the mysqldump
utility again, but this time with a command line option that
specifies we are only interested in dumping the DDL statements
required to create the schema:
% mysqldump --skip-add-drop-table --no-data <metastore_db_name> > my-schema-x.y.z.mysql.sql
4) The schema upgrade scripts assume that the schema you are upgrading
closely matches the official schema for your particular version of
Hive. The files in this directory with names like
"hive-schema-x.y.z.mysql.sql" contain dumps of the official schemas
corresponding to each of the released versions of Hive. You can
determine differences between your schema and the official schema
by diffing the contents of the official dump with the schema dump
you created in the previous step. Some differences are acceptable
and will not interfere with the upgrade process, but others need to
be resolved manually or the upgrade scripts will fail to complete.
* Missing Tables: Hive's default configuration causes the MetaStore
to create schema elements only when they are needed. Some tables
may be missing from your MetaStore schema if you have not created
the corresponding Hive catalog objects, e.g. the PARTITIONS table
will probably not exist if you have not created any table
partitions in your MetaStore. You MUST create these missing tables
before running the upgrade scripts. The easiest way to do this is
by executing the official schema DDL script against your
schema. Each of the CREATE TABLE statements in the schema script
include an IF NOT EXISTS clause, so tables which already exist in
your schema will be ignored, and those which don't exist will get
created.
* Extra Tables: Your schema may include a table named NUCLEUS_TABLES
or a table named SEQUENCE_TABLE. These tables are managed
by the DataNucleus ORM layer and will be created automatically if
they don't exist. No action on your part is required.
* Reversed Column Constraint Names in the Same Table: Tables with
multiple constraints may have the names of the constraints
reversed. For example, the PARTITIONS table contains two foreign
key constraints named PARTITIONS_FK1 and PARTITIONS_FK2 which
reference SDS.SD_ID and TBLS.TBL_ID respectively. However, in your
schema you may find that PARTITIONS_FK1 references TBLS.TBL_ID and
PARTITIONS_FK2 references SDS.SD_ID. Either version is acceptable
-- the only requirement is that these constraints actually exist.
* Differences in Column/Constraint Names: Your schema may contain
tables with columns named "IDX" or unique keys named
"UNIQUE<tab_name>". If you find either of these in your schema you
will need to change the names to "INTEGER_IDX" and
"UNIQUE_<tab_name>" before running the upgrade scripts. For more
background on this issue please refer to HIVE-1435.
5) You are now ready to run the schema upgrade scripts. If you are
upgrading from Hive 0.5.0 to Hive 0.6.0 you need to run the
upgrade-0.5.0-to-0.6.0.mysql.sql script, but if you are upgrading
from 0.5.0 to 0.7.0 you will need to run the 0.5.0 to 0.6.0 upgrade
script followed by the 0.6.0 to 0.7.0 upgrade script.
% mysql --verbose
mysql> use <metastore_db_name>;
Database changed
mysql> source upgrade-0.5.0-to-0.6.0.mysql.sql
mysql> source upgrade-0.6.0-to-0.7.0.mysql.sql
These scripts should run to completion without any errors. If you
do encounter errors you need to analyze the cause and attempt to
trace it back to one of the preceding steps.
6) The final step of the upgrade process is validating your freshly
upgraded schema against the official schema for your particular
version of Hive. This is accomplished by repeating steps (3) and
(4), but this time comparing against the official version of the
upgraded schema, e.g. if you upgraded the schema to Hive 0.7.0 then
you will want to compare your schema dump against the contents of
hive-schema-0.7.0.mysql.sql
直接说主要步骤：
一，最好先停止我们的hive相关服务，禁止访问hive的元数据 ，防止升级过程中其他应用使用修改数据。
二，备份元数据
三，开始升级，这里升级需要说明一下，hive提供的升级脚本是不能跨版本运行的，比如直接从1.2.2升级到2.3.4，所以我们需要根据它提供的脚本(脚本在scripts/metastore/upgrade/mysql)，一个大版本，一个大版本升级
如我这次 需要按照如下顺序执行
upgrade-1.2.0-to-2.0.0.mysql.sql
upgrade-2.0.0-to-2.1.0.mysql.sql
upgrade-2.1.0-to-2.2.0.mysql.sql
upgrade-2.2.0-to-2.3.0.mysql.sql
执行完后，再打开我们的apache-hive-2.3.4-bin就可以了。
