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new 8a73a0c2b484 [SPARK-57201][SQL] Skip the null check in
UnsafeProjection codegen for statically non-null values
8a73a0c2b484 is described below
commit 8a73a0c2b4848372c740c15db4f30578b97c9c52
Author: Gengliang Wang <[email protected]>
AuthorDate: Tue Jun 2 22:11:52 2026 -0700
[SPARK-57201][SQL] Skip the null check in UnsafeProjection codegen for
statically non-null values
### What changes were proposed in this pull request?
`GenerateUnsafeProjection` writes each field as `if (${input.isNull}) {
setNull } else { write }` whenever the field's schema is nullable. When the
bound value is statically non-null its `isNull` is the literal `false`, so this
emits a dead `if (false) { setNullAt(i); } else { write(...); }`.
This PR skips the null check (and the dead `setNull` branch) when
`input.isNull == FalseLiteral`, emitting just the write -- the same code the
existing `!nullable` path already produces. Symmetrically, when `input.isNull
== TrueLiteral` (statically null), it emits only `setNull`. The `FalseLiteral`
comparison is the idiom already used in this file for the top-level
`zeroOutNullBytes` fast path.
Before (for a non-null value in a nullable-schema field):
```java
if (false) {
rowWriter.setNullAt(0);
} else {
rowWriter.write(0, value);
}
```
After:
```java
rowWriter.write(0, value);
```
### Why are the changes needed?
Sub-task of SPARK-56908 (reduce generated Java size in whole-stage
codegen). Dumping the TPC-DS whole-stage codegen shows ~358 such dead `if
(false) { setNullAt } else { write }` blocks; the schema marks the field
nullable while the bound value is statically non-null. Emitting only the write
removes the dead branch and the redundant conditional from the generated
projection code.
### Does this PR introduce _any_ user-facing change?
No. The row writer's null bits are already cleared up front
(`resetRowWriter` / `zeroOutNullBytes`), so writing a non-null value without
`setNullAt` is exactly what the existing `!nullable` path does; results are
unchanged.
### How was this patch tested?
Behavior-preserving change covered by the existing projection suites:
`GeneratedProjectionSuite` and `UnsafeRowConverterSuite` (39 tests) pass.
Additionally verified by re-dumping the TPC-DS whole-stage codegen: the ~358
dead `if (false) { setNullAt }` blocks are gone and every generated subtree
still compiles.
### Was this patch authored or co-authored using generative AI tooling?
Generated-by: Claude Code (Opus 4.8)
Closes #56257 from gengliangwang/spark-unsafeproj-nullcheck.
Authored-by: Gengliang Wang <[email protected]>
Signed-off-by: Gengliang Wang <[email protected]>
---
.../expressions/codegen/GenerateUnsafeProjection.scala | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git
a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GenerateUnsafeProjection.scala
b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GenerateUnsafeProjection.scala
index 0f64eefe1a06..cf2902175ea7 100644
---
a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GenerateUnsafeProjection.scala
+++
b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GenerateUnsafeProjection.scala
@@ -119,11 +119,19 @@ object GenerateUnsafeProjection extends
CodeGenerator[Seq[Expression], UnsafePro
}
val writeField = writeElement(ctx, input.value, index.toString, dt,
rowWriter)
- if (!nullable) {
+ if (!nullable || input.isNull == FalseLiteral) {
+ // The value is statically known to be non-null, so skip the null
check and the
+ // (dead) setNull branch and just write the value.
s"""
|${input.code}
|${writeField.trim}
""".stripMargin
+ } else if (input.isNull == TrueLiteral) {
+ // The value is statically known to be null, so only set the null
bit.
+ s"""
+ |${input.code}
+ |${setNull.trim}
+ """.stripMargin
} else {
s"""
|${input.code}
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