From 92194c1e09bfa546c25aebb39d512434b8dcad95 Mon Sep 17 00:00:00 2001
From: Nhat Nguyen <nhat.nguyen@elastic.co>
Date: Wed, 28 Feb 2024 23:37:52 +0100
Subject: [PATCH 1/2] ProjectOperator should not retain block references

---
 .../compute/operator/ProjectOperator.java            | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/ProjectOperator.java b/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/ProjectOperator.java
index 2e61150061e1a..d318639625034 100644
--- a/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/ProjectOperator.java
+++ b/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/ProjectOperator.java
@@ -30,7 +30,7 @@ public String describe() {
     }
 
     private final int[] projection;
-    private Block[] blocks;
+    private final Block[] blocks;
 
     /**
      * Creates an operator that applies the given projection, encoded as an integer list where
@@ -41,6 +41,7 @@ public String describe() {
      */
     public ProjectOperator(List<Integer> projection) {
         this.projection = projection.stream().mapToInt(Integer::intValue).toArray();
+        this.blocks = new Block[projection.size()];
     }
 
     @Override
@@ -49,11 +50,6 @@ protected Page process(Page page) {
         if (blockCount == 0) {
             return page;
         }
-        if (blocks == null) {
-            blocks = new Block[projection.length];
-        }
-
-        Arrays.fill(blocks, null);
         int b = 0;
         for (int source : projection) {
             if (source >= blockCount) {
@@ -69,7 +65,9 @@ protected Page process(Page page) {
         page.releaseBlocks();
         // Use positionCount explicitly to avoid re-computing - also, if the projection is empty, there may be
         // no more blocks left to determine the positionCount from.
-        return new Page(positionCount, blocks);
+        Page output = new Page(positionCount, blocks);
+        Arrays.fill(blocks, null);
+        return output;
     }
 
     @Override

From d908097eefca1c38e9123f6c6b987e185f4ae30e Mon Sep 17 00:00:00 2001
From: Nhat Nguyen <nhat.nguyen@elastic.co>
Date: Wed, 28 Feb 2024 23:48:31 +0100
Subject: [PATCH 2/2] Update docs/changelog/105848.yaml

---
 docs/changelog/105848.yaml | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 docs/changelog/105848.yaml

diff --git a/docs/changelog/105848.yaml b/docs/changelog/105848.yaml
new file mode 100644
index 0000000000000..18291066177f6
--- /dev/null
+++ b/docs/changelog/105848.yaml
@@ -0,0 +1,5 @@
+pr: 105848
+summary: '`ProjectOperator` should not retain references to released blocks'
+area: ES|QL
+type: bug
+issues: []