Merge pull request #6 from andygrove/sunday

Add instructions for installing protoc and fix two compiler warnings

.github/workflows/jvm.yml

@@ -16,7 +16,9 @@ jobs:
 
     steps:
       - name: Install Protoc
-        uses: arduino/setup-protoc@master
+        uses: arduino/setup-protoc@v1
+        with:
+          version: '3.11.4'
       - name: Checkout Git branch
         uses: actions/checkout@v2
       - name: Set up JDK 1.8

README.md

@@ -35,6 +35,24 @@ The following expressions are supported:
 
 ## Installing Locally
 
+### Install the Google Protocol Buffer compiler
+
+The gradle build script uses the protobuf-gradle-plugin Gradle plugin to generate Java source code from the Ballista protobuf file and this depends on the protobuf compiler being installed.
+
+Use the following instructions to install the protobuf compiler on Ubuntu or similar Linux platforms.
+
+```bash
+wget https://github.com/protocolbuffers/protobuf/releases/download/v3.11.4/protobuf-all-3.11.4.tar.gz
+tar xzf protobuf-all-3.11.4.tar.gz
+cd protobuf-3.11.4/
+./configure
+make
+sudo make install
+sudo ldconfig
+```
+
+### Build libraries
+
 ```bash
 cd jvm
 ./gradlew publishToMavenLocal

jvm/examples/src/main/kotlin/ParallelQuery.kt

@@ -28,7 +28,7 @@ fun main() {
 
   val start = System.currentTimeMillis()
   val deferred =
-      (1..2).map { month ->
+      (1..12).map { month ->
         GlobalScope.async {
           val sql =
               "SELECT passenger_count, " +

jvm/executor/src/main/kotlin/BallistaFlightProducer.kt

@@ -53,8 +53,6 @@ class BallistaFlightProducer : FlightProducer {
 
       val allocator = RootAllocator(Long.MAX_VALUE)
 
-      var batchSize = 1024
-
       val root = VectorSchemaRoot.create(schema.toArrow(), allocator)
       listener.start(root, null)
 
@@ -66,7 +64,7 @@ class BallistaFlightProducer : FlightProducer {
         val rowCount = batch.rowCount()
         println("Received batch with $rowCount rows")
 
-        batchSize = rowCount
+        var batchSize = rowCount
         root.fieldVectors.forEach { it.setInitialCapacity(batchSize) }
         root.allocateNew()
 

jvm/fuzzer/src/main/kotlin/Fuzzer.kt

@@ -203,7 +203,7 @@ class EnhancedRandom(val rand: Random) {
   }
 
   fun nextString(len: Int): String {
-    return (0 until len).map { i -> rand.nextInt(charPool.size) }
+    return (0 until len).map { _ -> rand.nextInt(charPool.size) }
         .map(charPool::get)
         .joinToString("")
   }