[SPARK-17359][SQL][MLLIB] Use ArrayBuffer.+=(A) instead of ArrayBuffer.append(A) in performance critical paths

## What changes were proposed in this pull request?

We should generally use `ArrayBuffer.+=(A)` rather than `ArrayBuffer.append(A)`, because `append(A)` would involve extra boxing / unboxing.

## How was this patch tested?

N/A

Author: Liwei Lin <lwlin7@gmail.com>

Closes #14914 from lw-lin/append_to_plus_eq_v2.

4 files changed, 13 insertions, 13 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ExpressionSet.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ExpressionSet.scala
index 644a5b28a2..f93e5736de 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ExpressionSet.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ExpressionSet.scala
@@ -55,7 +55,7 @@ class ExpressionSet protected(
   protected def add(e: Expression): Unit = {
     if (!baseSet.contains(e.canonicalized)) {
       baseSet.add(e.canonicalized)
-      originals.append(e)
+      originals += e
     }
   }
 
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala
index 28064a5cfa..f982c222af 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala
@@ -596,12 +596,12 @@ class CodegenContext {
       // also not be too small, or it will have many function calls (for wide table), see the
       // results in BenchmarkWideTable.
       if (blockBuilder.length > 1024) {
-        blocks.append(blockBuilder.toString())
+        blocks += blockBuilder.toString()
         blockBuilder.clear()
       }
       blockBuilder.append(code)
     }
-    blocks.append(blockBuilder.toString())
+    blocks += blockBuilder.toString()
 
     if (blocks.length == 1) {
       // inline execution if only one block
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/QuantileSummaries.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/QuantileSummaries.scala
index 493b5faf9e..7512ace188 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/QuantileSummaries.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/QuantileSummaries.scala
@@ -59,7 +59,7 @@ class QuantileSummaries(
    * @param x the new observation to insert into the summary
    */
   def insert(x: Double): QuantileSummaries = {
-    headSampled.append(x)
+    headSampled += x
     if (headSampled.size >= defaultHeadSize) {
       this.withHeadBufferInserted
     } else {
@@ -90,7 +90,7 @@ class QuantileSummaries(
       val currentSample = sorted(opsIdx)
       // Add all the samples before the next observation.
       while(sampleIdx < sampled.size && sampled(sampleIdx).value <= currentSample) {
-        newSamples.append(sampled(sampleIdx))
+        newSamples += sampled(sampleIdx)
         sampleIdx += 1
       }
 
@@ -104,13 +104,13 @@ class QuantileSummaries(
         }
 
       val tuple = Stats(currentSample, 1, delta)
-      newSamples.append(tuple)
+      newSamples += tuple
       opsIdx += 1
     }
 
     // Add all the remaining existing samples
     while(sampleIdx < sampled.size) {
-      newSamples.append(sampled(sampleIdx))
+      newSamples += sampled(sampleIdx)
       sampleIdx += 1
     }
     new QuantileSummaries(compressThreshold, relativeError, newSamples.toArray, currentCount)
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/trees/TreeNodeSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/trees/TreeNodeSuite.scala
index 6a188e7e55..6246380dbe 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/trees/TreeNodeSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/trees/TreeNodeSuite.scala
@@ -82,8 +82,8 @@ class TreeNodeSuite extends SparkFunSuite {
     val expected = Seq("+", "1", "*", "2", "-", "3", "4")
     val expression = Add(Literal(1), Multiply(Literal(2), Subtract(Literal(3), Literal(4))))
     expression transformDown {
-      case b: BinaryOperator => actual.append(b.symbol); b
-      case l: Literal => actual.append(l.toString); l
+      case b: BinaryOperator => actual += b.symbol; b
+      case l: Literal => actual += l.toString; l
     }
 
     assert(expected === actual)
@@ -94,8 +94,8 @@ class TreeNodeSuite extends SparkFunSuite {
     val expected = Seq("1", "2", "3", "4", "-", "*", "+")
     val expression = Add(Literal(1), Multiply(Literal(2), Subtract(Literal(3), Literal(4))))
     expression transformUp {
-      case b: BinaryOperator => actual.append(b.symbol); b
-      case l: Literal => actual.append(l.toString); l
+      case b: BinaryOperator => actual += b.symbol; b
+      case l: Literal => actual += l.toString; l
     }
 
     assert(expected === actual)
@@ -134,8 +134,8 @@ class TreeNodeSuite extends SparkFunSuite {
     val expected = Seq("1", "2", "3", "4", "-", "*", "+")
     val expression = Add(Literal(1), Multiply(Literal(2), Subtract(Literal(3), Literal(4))))
     expression foreachUp {
-      case b: BinaryOperator => actual.append(b.symbol);
-      case l: Literal => actual.append(l.toString);
+      case b: BinaryOperator => actual += b.symbol;
+      case l: Literal => actual += l.toString;
     }
 
     assert(expected === actual)