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https://issues.apache.org/jira/browse/CASSANDRA-6704?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13902424#comment-13902424
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Edward Capriolo commented on CASSANDRA-6704:
--------------------------------------------
{quote}
Sort of, but there are some important differences: 1) as Brandon says, the code
is clearly vetted by the database dev team deploying triggers, which can't be
said here; and 2) we're all Java experts here, and the execution context is the
normal execution context of Cassandra, which again we're all familiar with.
Helping users with issues from dynamic class compilation / loading of languages
we don't understand is quite a different matter IMO, especially once sandboxing
is introduced (which really would be essential as C*'s internal APIs are not
safe to be accessed, nor protected, and could be used dangerously). It's not
clear to me this will be pain free from our side to ensure it always works,
either.
Also, with triggers we can more easily justify API breakages across minor/major
versions that require some work when upgrading, as they're well contained
within their Cassandra deployment, however if we expose internal APIs to client
code we will necessarily see more pushback on rapid development of these APIs,
as the difficulty for users to migrate will be increased.
{quote
You started the answer with "sorta". You are still allowing a user to put code
in the execution path. It is the exact same problem, if you let someone compile
dynamic code or you let the admin put the jar in a folder. You give someone the
potential to break something. All dynamic compiling does is make the result
faster to break and faster to fix.
{quote}
I think it's a pretty nice underlying goal, but it's a really heavyweight
feature that needs to be approached cautiously, and as Sylvain says, preferably
coherently.{quote}
Please do not imply that this feature is not coherent, or bad which has been
done several times already. This is a good feature.
{quote}I do wonder if it mightn't be possible to offer this as an easy to apply
patch in the meantime, outside of the main Apache repository. {quote}
Nice compromise but I do not the apache way. This option is forcing me into a
fork. This is a non breaking change. It is new feature. Cassandra is an open
source project. I am a user. I want a feature. Someone else on thread says
{quote}IMO, harnessing the invokeDynamic stuff in the JVM thusly could have
some compelling applications for us. {quote} I am not asking other developers
who make features with no votes to put changes and in forks you should not ask
me to do the same.
> Create wide row scanners
> ------------------------
>
> Key: CASSANDRA-6704
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6704
> Project: Cassandra
> Issue Type: New Feature
> Reporter: Edward Capriolo
> Assignee: Edward Capriolo
>
> The BigTable white paper demonstrates the use of scanners to iterate over
> rows and columns.
> http://static.googleusercontent.com/media/research.google.com/en/us/archive/bigtable-osdi06.pdf
> Because Cassandra does not have a primary sorting on row keys scanning over
> ranges of row keys is less useful.
> However we can use the scanner concept to operate on wide rows. For example
> many times a user wishes to do some custom processing inside a row and does
> not wish to carry the data across the network to do this processing.
> I have already implemented thrift methods to compile dynamic groovy code into
> Filters as well as some code that uses a Filter to page through and process
> data on the server side.
> https://github.com/edwardcapriolo/cassandra/compare/apache:trunk...trunk
> The following is a working code snippet.
> {code}
> @Test
> public void test_scanner() throws Exception
> {
> ColumnParent cp = new ColumnParent();
> cp.setColumn_family("Standard1");
> ByteBuffer key = ByteBuffer.wrap("rscannerkey".getBytes());
> for (char a='a'; a < 'g'; a++){
> Column c1 = new Column();
> c1.setName((a+"").getBytes());
> c1.setValue(new byte [0]);
> c1.setTimestamp(System.nanoTime());
> server.insert(key, cp, c1, ConsistencyLevel.ONE);
> }
>
> FilterDesc d = new FilterDesc();
> d.setSpec("GROOVY_CLASS_LOADER");
> d.setName("limit3");
> d.setCode("import org.apache.cassandra.dht.* \n" +
> "import org.apache.cassandra.thrift.* \n" +
> "public class Limit3 implements SFilter { \n " +
> "public FilterReturn filter(ColumnOrSuperColumn col,
> List<ColumnOrSuperColumn> filtered) {\n"+
> " filtered.add(col);\n"+
> " return filtered.size()< 3 ? FilterReturn.FILTER_MORE :
> FilterReturn.FILTER_DONE;\n"+
> "} \n" +
> "}\n");
> server.create_filter(d);
>
>
> ScannerResult res = server.create_scanner("Standard1", "limit3", key,
> ByteBuffer.wrap("a".getBytes()));
> Assert.assertEquals(3, res.results.size());
> }
> {code}
> I am going to be working on this code over the next few weeks but I wanted to
> get the concept our early so the design can see some criticism.
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