HappenLee opened a new issue #4376:
URL: https://github.com/apache/incubator-doris/issues/4376
## Motivation
At present, many customers need to access the external table through Doris,
but Doris only supports accessing the external table of MySQL at present. This
problem makes it difficult for users of other databases to use Doris.
**Open Database Connectivity** (**ODBC**) is a standard application
programming interface for accessing database management
systems:[https://en.wikipedia.org/wiki/Open_Database_Connectivity](https://en.wikipedia.org/wiki/Open_Database_Connectivity)
So should we support ODBC Scan node as a general external table access
method, it is provided to users. user can use **Driver Manager** of ODBC to
determine the databases that need to be accessed.
### It can bring us the following benefits:
1. First, Doris can eazily support a variety of different databases as
**external table**, likes: **Oracle, PostgreSQL, SQLServer**. Not only RDMS,
ODBC also support some NoSQL database. likes: **Redis, MongoDB**.
2. ODBC help Doris have a unified development interface instead of focusing
on the connection implementation of different databases.
3. **UNIX ODBC** is a static library based on LGPL, which can avoid the
commercial risk of using different database client APIs
## How To Use
It is very similar to the previous use of MySQL external table. The table
creation statement is as follows.
```
CREATE EXTERNAL TABLE `baseall_oracle` (
`k1` decimal(9, 3) NOT NULL COMMENT "",
`k2` char(10) NOT NULL COMMENT "",
`k3` datetime NOT NULL COMMENT "",
`k5` varchar(20) NOT NULL COMMENT "",
`k6` double NOT NULL COMMENT ""
) ENGINE=ODBC
PROPERTIES (
"host" = "192.168.1.2",
"port" = "4234",
"user" = "happenlee",
"password" = "happenlee",
"database" = "happen",
"table" = "baseall",
"driver" = "Oracle 19 ODBC driver",
"type" = "oracle"
);
```
Noted that it needs to add some additional info：
* **type**： To identify which database the table belongs to. For different
databases, there are some differences in ODBC connection and query.
* **driver**： To identify which odbc driver the table use. Use should
installed proper driver and config it in be/conf/odbcinst.ini like：
```
# Example driver definitions
# Driver from the postgresql-odbc package
# Setup from the unixODBC package
[PostgreSQL]
Description = ODBC for PostgreSQL
Driver = /usr/lib/psqlodbc.so
Setup = /usr/lib/libodbcpsqlS.so
Driver64 = /usr/lib64/psqlodbc.so
Setup64 = /usr/lib64/libodbcpsqlS.so
FileUsage = 1
# Driver from the mysql-connector-odbc package
# Setup from the unixODBC package
[MySQL ODBC 8.0 Unicode Driver]
Description = ODBC for MySQL
Driver =
/home/happen/mysql/mysql_odbc_rpm/usr/lib64/libmyodbc8w.so
FileUsage = 1
[Oracle 19 ODBC driver]
Description=Oracle ODBC driver for Oracle 19
Driver=/usr/lib/oracle/19.8/client64/lib/libsqora.so.19.1
Setup=
FileUsage=
CPTimeout=
CPReuse=
```
## Implementation
1. First, we should add third party static library of Unix ODBC.
2. Second，Modify thrift file to determine the interface of ODBC scan node.
like：
3. Modify the code of be part, implementation **ODBC_SCAN_NODE** and
**ODBC_SCANNER**
4. Modify the code of FE part to support adding external tables of ODBC
engine.
## Some Problem Need To Talk
1. Now the odbc driver of mysql have a function library conflict with
**mysql-server-mysql-5.7.18**，which may cause core of BE. So we should disable
WITH_MYSQL compile options，when we need to use ODBC_SCAN_NODE to connect mysql.
2. odbc scan node should support old external table of MySQL.
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