… btw thank you the all the work in laying this out. Best David
On Apr 25, 2013, at 11:10 PM, David Alves <[email protected]> wrote: > Hi Jacques > > I can take the RPC stuff. > Have you made any progress in Bit<>Bit comms? > > Best > David > > On Apr 25, 2013, at 11:06 PM, Jacques Nadeau <[email protected]> wrote: > >> I'm working on the execwork stuff and if someone would like to help out, >> here are a couple of things that need doing. I figured I'd drop them here >> and see if anyone wants to work on them in the next couple of days. If so, >> let me know otherwise I'll be picking them up soon. >> >> *RPC* >> - RPC Layer Handshakes: Currently, I haven't implemented the handshake that >> should happen in either the User <> Bit or the Bit <> Bit layer. The plan >> was to use an additional inserted event handler that removed itself from >> the event pipeline after a successful handshake or disconnected the channel >> on a failed handshake (with appropriate logging). The main validation at >> this point will be simply confirming that both endpoints are running on the >> same protocol version. The only other information that is currently >> needed is that that in the Bit <> Bit communication, the client should >> inform the server of its DrillEndpoint so that the server can then map that >> for future communication in the other direction. >> >> *DataTypes* >> - General Expansion: Currently, we have a hodgepodge of datatypes within >> the org.apache.drill.common.expression.types.DataType. We need to clean >> this up. There should be types that map to standard sql types. My >> thinking is that we should actually have separate types for each for >> nullable, non-nullable and repeated (required, optional and repeated in >> protobuf vernaciular) since we'll generally operate with those values >> completely differently (and that each type should reveal which it is). We >> should also have a relationship mapping from each to the other (e.g. how to >> convert a signed 32 bit int into a nullable signed 32 bit int. >> >> - Map Types: We don't need nullable but we will need different map types: >> inline and fieldwise. I think these will useful for the execution engine >> and will be leverage depending on the particular needs-- for example >> fieldwise will be a natural fit where we're operating on columnar data and >> doing an explode or other fieldwise nested operation and inline will be >> useful when we're doing things like sorting a complex field. Inline will >> also be appropriate where we have extremely sparse record sets. We'll just >> need transformation methods between the two variations. In the case of a >> fieldwise map type field, the field is virtual and only exists to contain >> its child fields. >> >> - Non-static DataTypes: We have a need types that don't fit the static data >> type model above. Examples include fixed width types (e.g. 10 byte >> string), polymorphic (inline encoded) types (number or string depending on >> record) and repeated nested versions of our other types. These are a >> little more gnarly as we need to support canonicalization of these. Optiq >> has some methods for how to handle this kind of type system so it probably >> makes sense to leverage that system. >> >> *Expression Type Materialization* >> - LogicalExpression type materialization: Right now, LogicalExpressions >> include support for late type binding. As part of the record batch >> execution path, these need to get materialized with correct casting, etc >> based on the actual found schema. As such, we need to have a function >> which takes a LogicalExpression tree, applies a materialized BatchSchema >> and returns a new LogicalExpression tree with full type settings. As part >> of this process, all types need to be cast as necessary and full validation >> of the tree should be done. Timothy has a pending work for validation >> specifically on a pull request that would be a good piece of code to >> leverage that need. We also have a visitor model for the expression tree >> that should be able to aid in the updated LogicalExpression construction. >> -LogicalExpression to Java expression conversion: We need to be able to >> convert our logical expressions into Java code expressions. Initially, >> this should be done in a simplistic way, using something like implicit >> boxing and the like just to get something working. This will likely be >> specialized per major type (nullable, non-nullable and repeated) and a >> framework might the most sense actually just distinguishing the >> LogicalExpression by these types. >> >> *JDBC* >> - The Drill JDBC driver layer needs to be updated to leverage our zookeeper >> coordination locations so that it can correctly find the cluster location. >> - The Drill JDBC driver should also manage reconnects so that if it loses >> connection with a particular Drillbit partner, that it will reconnect to >> another available node in the cluster. >> - Someone should point SQuirreL at Julian's latest work and see how things >> go... >> >> *ByteCode Engineering* >> - We need to put together a concrete class materialization strategy. My >> thinking for relational operators and code generation is that in most >> cases, we'll have an interface and a template class for a particular >> relational operator. We will build a template class that has all the >> generic stuff implemented but will make calls to empty methods where it >> expects lower level operations to occur. This allows things like the >> looping and certain types of null management to be fully materialized in >> source code without having to deal with the complexities of ByteCode >> generation. It also eases testing complexity. When a particular >> implementation is required, the Drillbit will be responsible for generating >> updated method bodies as required for the record-level expressions, marking >> all the methods and class as final, then loading the implementation into >> the query-level classloader. Note that the production Drillbit will never >> load the template class into the JVM and will simply utilize it in ByteCode >> form. I was hoping someone can take a look at trying to pull together a >> cohesive approach to doing this using ASM and Janino (likely utilizing the >> JDK commons-compiler mode). The interface should be pretty simple: input >> is an interface, a template class name, a set of (method_signature, >> method_body_text) objects and a varargs of objects that are required for >> object instantiation. The return should be an instance of the interface. >> The interface should check things like method_signature provided to >> available method blocks, the method blocks being replaced are empty, the >> object constructor matches the set of object argument provided by the >> object instantiation request, etc. >> >> *ByteBuf Improvements* >> - Our BufferAllocator should support child allocators (getChild()) with >> their own memory maximums and accounting (so we can determine the memory >> overhead to particular queries). We also need to be able to release entire >> child allocations at once. >> - We need to create a number of primitive type specific wrapping classes >> for ByteBuf. These additions include fixed offset indexing for operations >> (e.g. index 1 of an int buffer should be at 4 bytes), adding support for >> unsigned values (my preference would be to leverage the work in Guava if >> that makes sense) and modifying the hard bounds checks to softer assert >> checks to increase production performance. While we could do this >> utilizing the ByteBuf interface, from everything I've experienced and read, >> we need to minimize issues with inlining and performance so we really need >> to be able to modify/refer to PooledUnsafeDirectByteBuf directly for the >> wrapping classes. Of course, it is a final package private class. Short >> term that means we really need to create a number of specific buffer types >> that wrap it and just put them in the io.netty.buffer package (or >> alternatively create a Drill version or wrapper). >
