- came from PL/J
- pl/j was written 14 years ago by Laszlo Hornyak
- competed with pl/java and lost the VHS/Betamax discussion
- since then while working at Pivotal I helped write pl/container
- PL/Container - GPDB execution sandboxing using docker containers for Python and R
- all of these provide what is referred to as a "trusted" language in PostgreSQL.
- trusted languages are prevented from harming the database by either directly accessing the filesystem or reading others data.
- also PostgreSQL allows developers to create trusted language functions without being a superuser.
- well mostly because I could and I had some free time.
- almost all of the work on the server was done and debugged
- netty makes it somewhat easy (after you grok netty).
-
On the server side you create a language called pl/jvm
-
languages are nothing more than a call handler written in C which intercepts a call and has information about
- return type
- arguments
- function definition
-
Once control is transferred to the function handler then the fun begins
- create a call request object with the arguments
- send the call request to the Java program using a binary protocol which is very similar to PostgreSQL protocol
- control is transferred to the Java code which
- decodes the request
- instantiates the function and calls the method defined in the function call
- encodes the response and sends it back
- returns control back to the C code in the server
- currently the code can deal with any base type and arrays of base types
- working on UDT's but have the issue of how to figure out the postgresql type -> java type mapping
- synchronous notification of data changes
- alternatives pl/java Logical Decoding.
- what makes it so special it can be used with any JVM based language
- performance
- looks like the overhead is around 1ms.
- 10000 iterations of calling a sql function to add two numbers takes .193 ms per call
-
select i+j; $$ LANGUAGE sql;``` - 10000 iterations of calling a pljvm function to add two numbers takes 1.105 ms per call
-
org.postgresql.plj.test.Int.add $$ LANGUAGE pljvm;```
- need help with
- classpath separation
- since calls are being handled by the same JVM don't want to leak data from one postgresql process to another
- library or full fledged application?
- currently the library could be used by any JVM easily
- how to pass UDT's where do I get the package name from
- the problem is that we can't pass package information along with the name of the UDT
- autoboxing ?
- how to call a method defined as public int add(int i, int j) or public Integer add(Integer i, Integer j)