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Debug Hadoop 3.2 profile #24

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@HyukjinKwon HyukjinKwon closed this Oct 6, 2020
@HyukjinKwon HyukjinKwon deleted the SPARK-29250-debug branch December 7, 2020 02:07
HyukjinKwon pushed a commit that referenced this pull request Dec 21, 2020
…ries if AQE is enabled

### What changes were proposed in this pull request?

This PR fixes an issue that when AQE is enabled, EXPLAIN FORMATTED doesn't show the plan for subqueries.

```scala
val df = spark.range(1, 100)
df.createTempView("df")
spark.sql("SELECT (SELECT min(id) AS v FROM df)").explain("FORMATTED")

== Physical Plan ==
AdaptiveSparkPlan (3)
+- Project (2)
 +- Scan OneRowRelation (1)

(1) Scan OneRowRelation
Output: []
Arguments: ParallelCollectionRDD[0] at explain at <console>:24, OneRowRelation, UnknownPartitioning(0)

(2) Project
Output [1]: [Subquery subquery#3, [id=#20] AS scalarsubquery()#5L]
Input: []

(3) AdaptiveSparkPlan
Output [1]: [scalarsubquery()#5L]
Arguments: isFinalPlan=false
```

After this change, the plan for the subquerie is shown.
```scala
== Physical Plan ==
* Project (2)
+- * Scan OneRowRelation (1)

(1) Scan OneRowRelation [codegen id : 1]
Output: []
Arguments: ParallelCollectionRDD[0] at explain at <console>:24, OneRowRelation, UnknownPartitioning(0)

(2) Project [codegen id : 1]
Output [1]: [Subquery scalar-subquery#3, [id=#24] AS scalarsubquery()#5L]
Input: []

===== Subqueries =====

Subquery:1 Hosting operator id = 2 Hosting Expression = Subquery scalar-subquery#3, [id=#24]
* HashAggregate (6)
+- Exchange (5)
   +- * HashAggregate (4)
      +- * Range (3)

(3) Range [codegen id : 1]
Output [1]: [id#0L]
Arguments: Range (1, 100, step=1, splits=Some(12))

(4) HashAggregate [codegen id : 1]
Input [1]: [id#0L]
Keys: []
Functions [1]: [partial_min(id#0L)]
Aggregate Attributes [1]: [min#7L]
Results [1]: [min#8L]

(5) Exchange
Input [1]: [min#8L]
Arguments: SinglePartition, ENSURE_REQUIREMENTS, [id=#20]

(6) HashAggregate [codegen id : 2]
Input [1]: [min#8L]
Keys: []
Functions [1]: [min(id#0L)]
Aggregate Attributes [1]: [min(id#0L)#4L]
Results [1]: [min(id#0L)#4L AS v#2L]
```

### Why are the changes needed?

For better debuggability.

### Does this PR introduce _any_ user-facing change?

Yes. Users can see the formatted plan for subqueries.

### How was this patch tested?

New test.

Closes apache#30855 from sarutak/fix-aqe-explain.

Authored-by: Kousuke Saruta <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>
HyukjinKwon pushed a commit that referenced this pull request Dec 21, 2020
…subquery code

### What changes were proposed in this pull request?

This PR fixes an issue that `EXPLAIN CODEGEN` and `BenchmarkQueryTest` don't show the corresponding code for subqueries.

The following example is about `EXPLAIN CODEGEN`.
```
spark.conf.set("spark.sql.adaptive.enabled", "false")
val df = spark.range(1, 100)
df.createTempView("df")
spark.sql("SELECT (SELECT min(id) AS v FROM df)").explain("CODEGEN")

scala> spark.sql("SELECT (SELECT min(id) AS v FROM df)").explain("CODEGEN")
Found 1 WholeStageCodegen subtrees.
== Subtree 1 / 1 (maxMethodCodeSize:55; maxConstantPoolSize:97(0.15% used); numInnerClasses:0) ==
*(1) Project [Subquery scalar-subquery#3, [id=#24] AS scalarsubquery()#5L]
:  +- Subquery scalar-subquery#3, [id=#24]
:     +- *(2) HashAggregate(keys=[], functions=[min(id#0L)], output=[v#2L])
:        +- Exchange SinglePartition, ENSURE_REQUIREMENTS, [id=#20]
:           +- *(1) HashAggregate(keys=[], functions=[partial_min(id#0L)], output=[min#8L])
:              +- *(1) Range (1, 100, step=1, splits=12)
+- *(1) Scan OneRowRelation[]

Generated code:
/* 001 */ public Object generate(Object[] references) {
/* 002 */   return new GeneratedIteratorForCodegenStage1(references);
/* 003 */ }
/* 004 */
/* 005 */ // codegenStageId=1
/* 006 */ final class GeneratedIteratorForCodegenStage1 extends org.apache.spark.sql.execution.BufferedRowIterator {
/* 007 */   private Object[] references;
/* 008 */   private scala.collection.Iterator[] inputs;
/* 009 */   private scala.collection.Iterator rdd_input_0;
/* 010 */   private org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter[] project_mutableStateArray_0 = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter[1];
/* 011 */
/* 012 */   public GeneratedIteratorForCodegenStage1(Object[] references) {
/* 013 */     this.references = references;
/* 014 */   }
/* 015 */
/* 016 */   public void init(int index, scala.collection.Iterator[] inputs) {
/* 017 */     partitionIndex = index;
/* 018 */     this.inputs = inputs;
/* 019 */     rdd_input_0 = inputs[0];
/* 020 */     project_mutableStateArray_0[0] = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter(1, 0);
/* 021 */
/* 022 */   }
/* 023 */
/* 024 */   private void project_doConsume_0() throws java.io.IOException {
/* 025 */     // common sub-expressions
/* 026 */
/* 027 */     project_mutableStateArray_0[0].reset();
/* 028 */
/* 029 */     if (false) {
/* 030 */       project_mutableStateArray_0[0].setNullAt(0);
/* 031 */     } else {
/* 032 */       project_mutableStateArray_0[0].write(0, 1L);
/* 033 */     }
/* 034 */     append((project_mutableStateArray_0[0].getRow()));
/* 035 */
/* 036 */   }
/* 037 */
/* 038 */   protected void processNext() throws java.io.IOException {
/* 039 */     while ( rdd_input_0.hasNext()) {
/* 040 */       InternalRow rdd_row_0 = (InternalRow) rdd_input_0.next();
/* 041 */       ((org.apache.spark.sql.execution.metric.SQLMetric) references[0] /* numOutputRows */).add(1);
/* 042 */       project_doConsume_0();
/* 043 */       if (shouldStop()) return;
/* 044 */     }
/* 045 */   }
/* 046 */
/* 047 */ }
```

After this change, the corresponding code for subqueries are shown.
```
Found 3 WholeStageCodegen subtrees.
== Subtree 1 / 3 (maxMethodCodeSize:282; maxConstantPoolSize:206(0.31% used); numInnerClasses:0) ==
*(1) HashAggregate(keys=[], functions=[partial_min(id#0L)], output=[min#8L])
+- *(1) Range (1, 100, step=1, splits=12)

Generated code:
/* 001 */ public Object generate(Object[] references) {
/* 002 */   return new GeneratedIteratorForCodegenStage1(references);
/* 003 */ }
/* 004 */
/* 005 */ // codegenStageId=1
/* 006 */ final class GeneratedIteratorForCodegenStage1 extends org.apache.spark.sql.execution.BufferedRowIterator {
/* 007 */   private Object[] references;
/* 008 */   private scala.collection.Iterator[] inputs;
/* 009 */   private boolean agg_initAgg_0;
/* 010 */   private boolean agg_bufIsNull_0;
/* 011 */   private long agg_bufValue_0;
/* 012 */   private boolean range_initRange_0;
/* 013 */   private long range_nextIndex_0;
/* 014 */   private TaskContext range_taskContext_0;
/* 015 */   private InputMetrics range_inputMetrics_0;
/* 016 */   private long range_batchEnd_0;
/* 017 */   private long range_numElementsTodo_0;
/* 018 */   private boolean agg_agg_isNull_2_0;
/* 019 */   private org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter[] range_mutableStateArray_0 = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter[3];
/* 020 */
/* 021 */   public GeneratedIteratorForCodegenStage1(Object[] references) {
/* 022 */     this.references = references;
/* 023 */   }
/* 024 */
/* 025 */   public void init(int index, scala.collection.Iterator[] inputs) {
/* 026 */     partitionIndex = index;
/* 027 */     this.inputs = inputs;
/* 028 */
/* 029 */     range_taskContext_0 = TaskContext.get();
/* 030 */     range_inputMetrics_0 = range_taskContext_0.taskMetrics().inputMetrics();
/* 031 */     range_mutableStateArray_0[0] = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter(1, 0);
/* 032 */     range_mutableStateArray_0[1] = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter(1, 0);
/* 033 */     range_mutableStateArray_0[2] = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter(1, 0);
/* 034 */
/* 035 */   }
/* 036 */
/* 037 */   private void agg_doAggregateWithoutKey_0() throws java.io.IOException {
/* 038 */     // initialize aggregation buffer
/* 039 */     agg_bufIsNull_0 = true;
/* 040 */     agg_bufValue_0 = -1L;
/* 041 */
/* 042 */     // initialize Range
/* 043 */     if (!range_initRange_0) {
/* 044 */       range_initRange_0 = true;
/* 045 */       initRange(partitionIndex);
/* 046 */     }
/* 047 */
/* 048 */     while (true) {
/* 049 */       if (range_nextIndex_0 == range_batchEnd_0) {
/* 050 */         long range_nextBatchTodo_0;
/* 051 */         if (range_numElementsTodo_0 > 1000L) {
/* 052 */           range_nextBatchTodo_0 = 1000L;
/* 053 */           range_numElementsTodo_0 -= 1000L;
/* 054 */         } else {
/* 055 */           range_nextBatchTodo_0 = range_numElementsTodo_0;
/* 056 */           range_numElementsTodo_0 = 0;
/* 057 */           if (range_nextBatchTodo_0 == 0) break;
/* 058 */         }
/* 059 */         range_batchEnd_0 += range_nextBatchTodo_0 * 1L;
/* 060 */       }
/* 061 */
/* 062 */       int range_localEnd_0 = (int)((range_batchEnd_0 - range_nextIndex_0) / 1L);
/* 063 */       for (int range_localIdx_0 = 0; range_localIdx_0 < range_localEnd_0; range_localIdx_0++) {
/* 064 */         long range_value_0 = ((long)range_localIdx_0 * 1L) + range_nextIndex_0;
/* 065 */
/* 066 */         agg_doConsume_0(range_value_0);
/* 067 */
/* 068 */         // shouldStop check is eliminated
/* 069 */       }
/* 070 */       range_nextIndex_0 = range_batchEnd_0;
/* 071 */       ((org.apache.spark.sql.execution.metric.SQLMetric) references[0] /* numOutputRows */).add(range_localEnd_0);
/* 072 */       range_inputMetrics_0.incRecordsRead(range_localEnd_0);
/* 073 */       range_taskContext_0.killTaskIfInterrupted();
/* 074 */     }
/* 075 */
/* 076 */   }
/* 077 */
/* 078 */   private void initRange(int idx) {
/* 079 */     java.math.BigInteger index = java.math.BigInteger.valueOf(idx);
/* 080 */     java.math.BigInteger numSlice = java.math.BigInteger.valueOf(12L);
/* 081 */     java.math.BigInteger numElement = java.math.BigInteger.valueOf(99L);
/* 082 */     java.math.BigInteger step = java.math.BigInteger.valueOf(1L);
/* 083 */     java.math.BigInteger start = java.math.BigInteger.valueOf(1L);
/* 084 */     long partitionEnd;
/* 085 */
/* 086 */     java.math.BigInteger st = index.multiply(numElement).divide(numSlice).multiply(step).add(start);
/* 087 */     if (st.compareTo(java.math.BigInteger.valueOf(Long.MAX_VALUE)) > 0) {
/* 088 */       range_nextIndex_0 = Long.MAX_VALUE;
/* 089 */     } else if (st.compareTo(java.math.BigInteger.valueOf(Long.MIN_VALUE)) < 0) {
/* 090 */       range_nextIndex_0 = Long.MIN_VALUE;
/* 091 */     } else {
/* 092 */       range_nextIndex_0 = st.longValue();
/* 093 */     }
/* 094 */     range_batchEnd_0 = range_nextIndex_0;
/* 095 */
/* 096 */     java.math.BigInteger end = index.add(java.math.BigInteger.ONE).multiply(numElement).divide(numSlice)
/* 097 */     .multiply(step).add(start);
/* 098 */     if (end.compareTo(java.math.BigInteger.valueOf(Long.MAX_VALUE)) > 0) {
/* 099 */       partitionEnd = Long.MAX_VALUE;
/* 100 */     } else if (end.compareTo(java.math.BigInteger.valueOf(Long.MIN_VALUE)) < 0) {
/* 101 */       partitionEnd = Long.MIN_VALUE;
/* 102 */     } else {
/* 103 */       partitionEnd = end.longValue();
/* 104 */     }
/* 105 */
/* 106 */     java.math.BigInteger startToEnd = java.math.BigInteger.valueOf(partitionEnd).subtract(
/* 107 */       java.math.BigInteger.valueOf(range_nextIndex_0));
/* 108 */     range_numElementsTodo_0  = startToEnd.divide(step).longValue();
/* 109 */     if (range_numElementsTodo_0 < 0) {
/* 110 */       range_numElementsTodo_0 = 0;
/* 111 */     } else if (startToEnd.remainder(step).compareTo(java.math.BigInteger.valueOf(0L)) != 0) {
/* 112 */       range_numElementsTodo_0++;
/* 113 */     }
/* 114 */   }
/* 115 */
/* 116 */   private void agg_doConsume_0(long agg_expr_0_0) throws java.io.IOException {
/* 117 */     // do aggregate
/* 118 */     // common sub-expressions
/* 119 */
/* 120 */     // evaluate aggregate functions and update aggregation buffers
/* 121 */
/* 122 */     agg_agg_isNull_2_0 = true;
/* 123 */     long agg_value_2 = -1L;
/* 124 */
/* 125 */     if (!agg_bufIsNull_0 && (agg_agg_isNull_2_0 ||
/* 126 */         agg_value_2 > agg_bufValue_0)) {
/* 127 */       agg_agg_isNull_2_0 = false;
/* 128 */       agg_value_2 = agg_bufValue_0;
/* 129 */     }
/* 130 */
/* 131 */     if (!false && (agg_agg_isNull_2_0 ||
/* 132 */         agg_value_2 > agg_expr_0_0)) {
/* 133 */       agg_agg_isNull_2_0 = false;
/* 134 */       agg_value_2 = agg_expr_0_0;
/* 135 */     }
/* 136 */
/* 137 */     agg_bufIsNull_0 = agg_agg_isNull_2_0;
/* 138 */     agg_bufValue_0 = agg_value_2;
/* 139 */
/* 140 */   }
/* 141 */
/* 142 */   protected void processNext() throws java.io.IOException {
/* 143 */     while (!agg_initAgg_0) {
/* 144 */       agg_initAgg_0 = true;
/* 145 */       long agg_beforeAgg_0 = System.nanoTime();
/* 146 */       agg_doAggregateWithoutKey_0();
/* 147 */       ((org.apache.spark.sql.execution.metric.SQLMetric) references[2] /* aggTime */).add((System.nanoTime() - agg_beforeAgg_0) / 1000000);
/* 148 */
/* 149 */       // output the result
/* 150 */
/* 151 */       ((org.apache.spark.sql.execution.metric.SQLMetric) references[1] /* numOutputRows */).add(1);
/* 152 */       range_mutableStateArray_0[2].reset();
/* 153 */
/* 154 */       range_mutableStateArray_0[2].zeroOutNullBytes();
/* 155 */
/* 156 */       if (agg_bufIsNull_0) {
/* 157 */         range_mutableStateArray_0[2].setNullAt(0);
/* 158 */       } else {
/* 159 */         range_mutableStateArray_0[2].write(0, agg_bufValue_0);
/* 160 */       }
/* 161 */       append((range_mutableStateArray_0[2].getRow()));
/* 162 */     }
/* 163 */   }
/* 164 */
/* 165 */ }
```

### Why are the changes needed?

For better debuggability.

### Does this PR introduce _any_ user-facing change?

Yes. After this change, users can see subquery code by `EXPLAIN CODEGEN`.

### How was this patch tested?

New test.

Closes apache#30859 from sarutak/explain-codegen-subqueries.

Authored-by: Kousuke Saruta <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>
HyukjinKwon pushed a commit that referenced this pull request Jan 12, 2021
…ries if AQE is enabled

### What changes were proposed in this pull request?

This PR fixes an issue that when AQE is enabled, EXPLAIN FORMATTED doesn't show the plan for subqueries.

```scala
val df = spark.range(1, 100)
df.createTempView("df")
spark.sql("SELECT (SELECT min(id) AS v FROM df)").explain("FORMATTED")

== Physical Plan ==
AdaptiveSparkPlan (3)
+- Project (2)
 +- Scan OneRowRelation (1)

(1) Scan OneRowRelation
Output: []
Arguments: ParallelCollectionRDD[0] at explain at <console>:24, OneRowRelation, UnknownPartitioning(0)

(2) Project
Output [1]: [Subquery subquery#3, [id=#20] AS scalarsubquery()#5L]
Input: []

(3) AdaptiveSparkPlan
Output [1]: [scalarsubquery()#5L]
Arguments: isFinalPlan=false
```

After this change, the plan for the subquerie is shown.
```scala
== Physical Plan ==
* Project (2)
+- * Scan OneRowRelation (1)

(1) Scan OneRowRelation [codegen id : 1]
Output: []
Arguments: ParallelCollectionRDD[0] at explain at <console>:24, OneRowRelation, UnknownPartitioning(0)

(2) Project [codegen id : 1]
Output [1]: [Subquery scalar-subquery#3, [id=#24] AS scalarsubquery()#5L]
Input: []

===== Subqueries =====

Subquery:1 Hosting operator id = 2 Hosting Expression = Subquery scalar-subquery#3, [id=#24]
* HashAggregate (6)
+- Exchange (5)
   +- * HashAggregate (4)
      +- * Range (3)

(3) Range [codegen id : 1]
Output [1]: [id#0L]
Arguments: Range (1, 100, step=1, splits=Some(12))

(4) HashAggregate [codegen id : 1]
Input [1]: [id#0L]
Keys: []
Functions [1]: [partial_min(id#0L)]
Aggregate Attributes [1]: [min#7L]
Results [1]: [min#8L]

(5) Exchange
Input [1]: [min#8L]
Arguments: SinglePartition, ENSURE_REQUIREMENTS, [id=#20]

(6) HashAggregate [codegen id : 2]
Input [1]: [min#8L]
Keys: []
Functions [1]: [min(id#0L)]
Aggregate Attributes [1]: [min(id#0L)#4L]
Results [1]: [min(id#0L)#4L AS v#2L]
```

### Why are the changes needed?

For better debuggability.

### Does this PR introduce _any_ user-facing change?

Yes. Users can see the formatted plan for subqueries.

### How was this patch tested?

New test.

Closes apache#30855 from sarutak/fix-aqe-explain.

Authored-by: Kousuke Saruta <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>
(cherry picked from commit 70da86a)
Signed-off-by: Dongjoon Hyun <[email protected]>
HyukjinKwon pushed a commit that referenced this pull request Jan 12, 2021
…subquery code

### What changes were proposed in this pull request?

This PR fixes an issue that `EXPLAIN CODEGEN` and `BenchmarkQueryTest` don't show the corresponding code for subqueries.

The following example is about `EXPLAIN CODEGEN`.
```
spark.conf.set("spark.sql.adaptive.enabled", "false")
val df = spark.range(1, 100)
df.createTempView("df")
spark.sql("SELECT (SELECT min(id) AS v FROM df)").explain("CODEGEN")

scala> spark.sql("SELECT (SELECT min(id) AS v FROM df)").explain("CODEGEN")
Found 1 WholeStageCodegen subtrees.
== Subtree 1 / 1 (maxMethodCodeSize:55; maxConstantPoolSize:97(0.15% used); numInnerClasses:0) ==
*(1) Project [Subquery scalar-subquery#3, [id=#24] AS scalarsubquery()#5L]
:  +- Subquery scalar-subquery#3, [id=#24]
:     +- *(2) HashAggregate(keys=[], functions=[min(id#0L)], output=[v#2L])
:        +- Exchange SinglePartition, ENSURE_REQUIREMENTS, [id=#20]
:           +- *(1) HashAggregate(keys=[], functions=[partial_min(id#0L)], output=[min#8L])
:              +- *(1) Range (1, 100, step=1, splits=12)
+- *(1) Scan OneRowRelation[]

Generated code:
/* 001 */ public Object generate(Object[] references) {
/* 002 */   return new GeneratedIteratorForCodegenStage1(references);
/* 003 */ }
/* 004 */
/* 005 */ // codegenStageId=1
/* 006 */ final class GeneratedIteratorForCodegenStage1 extends org.apache.spark.sql.execution.BufferedRowIterator {
/* 007 */   private Object[] references;
/* 008 */   private scala.collection.Iterator[] inputs;
/* 009 */   private scala.collection.Iterator rdd_input_0;
/* 010 */   private org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter[] project_mutableStateArray_0 = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter[1];
/* 011 */
/* 012 */   public GeneratedIteratorForCodegenStage1(Object[] references) {
/* 013 */     this.references = references;
/* 014 */   }
/* 015 */
/* 016 */   public void init(int index, scala.collection.Iterator[] inputs) {
/* 017 */     partitionIndex = index;
/* 018 */     this.inputs = inputs;
/* 019 */     rdd_input_0 = inputs[0];
/* 020 */     project_mutableStateArray_0[0] = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter(1, 0);
/* 021 */
/* 022 */   }
/* 023 */
/* 024 */   private void project_doConsume_0() throws java.io.IOException {
/* 025 */     // common sub-expressions
/* 026 */
/* 027 */     project_mutableStateArray_0[0].reset();
/* 028 */
/* 029 */     if (false) {
/* 030 */       project_mutableStateArray_0[0].setNullAt(0);
/* 031 */     } else {
/* 032 */       project_mutableStateArray_0[0].write(0, 1L);
/* 033 */     }
/* 034 */     append((project_mutableStateArray_0[0].getRow()));
/* 035 */
/* 036 */   }
/* 037 */
/* 038 */   protected void processNext() throws java.io.IOException {
/* 039 */     while ( rdd_input_0.hasNext()) {
/* 040 */       InternalRow rdd_row_0 = (InternalRow) rdd_input_0.next();
/* 041 */       ((org.apache.spark.sql.execution.metric.SQLMetric) references[0] /* numOutputRows */).add(1);
/* 042 */       project_doConsume_0();
/* 043 */       if (shouldStop()) return;
/* 044 */     }
/* 045 */   }
/* 046 */
/* 047 */ }
```

After this change, the corresponding code for subqueries are shown.
```
Found 3 WholeStageCodegen subtrees.
== Subtree 1 / 3 (maxMethodCodeSize:282; maxConstantPoolSize:206(0.31% used); numInnerClasses:0) ==
*(1) HashAggregate(keys=[], functions=[partial_min(id#0L)], output=[min#8L])
+- *(1) Range (1, 100, step=1, splits=12)

Generated code:
/* 001 */ public Object generate(Object[] references) {
/* 002 */   return new GeneratedIteratorForCodegenStage1(references);
/* 003 */ }
/* 004 */
/* 005 */ // codegenStageId=1
/* 006 */ final class GeneratedIteratorForCodegenStage1 extends org.apache.spark.sql.execution.BufferedRowIterator {
/* 007 */   private Object[] references;
/* 008 */   private scala.collection.Iterator[] inputs;
/* 009 */   private boolean agg_initAgg_0;
/* 010 */   private boolean agg_bufIsNull_0;
/* 011 */   private long agg_bufValue_0;
/* 012 */   private boolean range_initRange_0;
/* 013 */   private long range_nextIndex_0;
/* 014 */   private TaskContext range_taskContext_0;
/* 015 */   private InputMetrics range_inputMetrics_0;
/* 016 */   private long range_batchEnd_0;
/* 017 */   private long range_numElementsTodo_0;
/* 018 */   private boolean agg_agg_isNull_2_0;
/* 019 */   private org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter[] range_mutableStateArray_0 = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter[3];
/* 020 */
/* 021 */   public GeneratedIteratorForCodegenStage1(Object[] references) {
/* 022 */     this.references = references;
/* 023 */   }
/* 024 */
/* 025 */   public void init(int index, scala.collection.Iterator[] inputs) {
/* 026 */     partitionIndex = index;
/* 027 */     this.inputs = inputs;
/* 028 */
/* 029 */     range_taskContext_0 = TaskContext.get();
/* 030 */     range_inputMetrics_0 = range_taskContext_0.taskMetrics().inputMetrics();
/* 031 */     range_mutableStateArray_0[0] = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter(1, 0);
/* 032 */     range_mutableStateArray_0[1] = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter(1, 0);
/* 033 */     range_mutableStateArray_0[2] = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter(1, 0);
/* 034 */
/* 035 */   }
/* 036 */
/* 037 */   private void agg_doAggregateWithoutKey_0() throws java.io.IOException {
/* 038 */     // initialize aggregation buffer
/* 039 */     agg_bufIsNull_0 = true;
/* 040 */     agg_bufValue_0 = -1L;
/* 041 */
/* 042 */     // initialize Range
/* 043 */     if (!range_initRange_0) {
/* 044 */       range_initRange_0 = true;
/* 045 */       initRange(partitionIndex);
/* 046 */     }
/* 047 */
/* 048 */     while (true) {
/* 049 */       if (range_nextIndex_0 == range_batchEnd_0) {
/* 050 */         long range_nextBatchTodo_0;
/* 051 */         if (range_numElementsTodo_0 > 1000L) {
/* 052 */           range_nextBatchTodo_0 = 1000L;
/* 053 */           range_numElementsTodo_0 -= 1000L;
/* 054 */         } else {
/* 055 */           range_nextBatchTodo_0 = range_numElementsTodo_0;
/* 056 */           range_numElementsTodo_0 = 0;
/* 057 */           if (range_nextBatchTodo_0 == 0) break;
/* 058 */         }
/* 059 */         range_batchEnd_0 += range_nextBatchTodo_0 * 1L;
/* 060 */       }
/* 061 */
/* 062 */       int range_localEnd_0 = (int)((range_batchEnd_0 - range_nextIndex_0) / 1L);
/* 063 */       for (int range_localIdx_0 = 0; range_localIdx_0 < range_localEnd_0; range_localIdx_0++) {
/* 064 */         long range_value_0 = ((long)range_localIdx_0 * 1L) + range_nextIndex_0;
/* 065 */
/* 066 */         agg_doConsume_0(range_value_0);
/* 067 */
/* 068 */         // shouldStop check is eliminated
/* 069 */       }
/* 070 */       range_nextIndex_0 = range_batchEnd_0;
/* 071 */       ((org.apache.spark.sql.execution.metric.SQLMetric) references[0] /* numOutputRows */).add(range_localEnd_0);
/* 072 */       range_inputMetrics_0.incRecordsRead(range_localEnd_0);
/* 073 */       range_taskContext_0.killTaskIfInterrupted();
/* 074 */     }
/* 075 */
/* 076 */   }
/* 077 */
/* 078 */   private void initRange(int idx) {
/* 079 */     java.math.BigInteger index = java.math.BigInteger.valueOf(idx);
/* 080 */     java.math.BigInteger numSlice = java.math.BigInteger.valueOf(12L);
/* 081 */     java.math.BigInteger numElement = java.math.BigInteger.valueOf(99L);
/* 082 */     java.math.BigInteger step = java.math.BigInteger.valueOf(1L);
/* 083 */     java.math.BigInteger start = java.math.BigInteger.valueOf(1L);
/* 084 */     long partitionEnd;
/* 085 */
/* 086 */     java.math.BigInteger st = index.multiply(numElement).divide(numSlice).multiply(step).add(start);
/* 087 */     if (st.compareTo(java.math.BigInteger.valueOf(Long.MAX_VALUE)) > 0) {
/* 088 */       range_nextIndex_0 = Long.MAX_VALUE;
/* 089 */     } else if (st.compareTo(java.math.BigInteger.valueOf(Long.MIN_VALUE)) < 0) {
/* 090 */       range_nextIndex_0 = Long.MIN_VALUE;
/* 091 */     } else {
/* 092 */       range_nextIndex_0 = st.longValue();
/* 093 */     }
/* 094 */     range_batchEnd_0 = range_nextIndex_0;
/* 095 */
/* 096 */     java.math.BigInteger end = index.add(java.math.BigInteger.ONE).multiply(numElement).divide(numSlice)
/* 097 */     .multiply(step).add(start);
/* 098 */     if (end.compareTo(java.math.BigInteger.valueOf(Long.MAX_VALUE)) > 0) {
/* 099 */       partitionEnd = Long.MAX_VALUE;
/* 100 */     } else if (end.compareTo(java.math.BigInteger.valueOf(Long.MIN_VALUE)) < 0) {
/* 101 */       partitionEnd = Long.MIN_VALUE;
/* 102 */     } else {
/* 103 */       partitionEnd = end.longValue();
/* 104 */     }
/* 105 */
/* 106 */     java.math.BigInteger startToEnd = java.math.BigInteger.valueOf(partitionEnd).subtract(
/* 107 */       java.math.BigInteger.valueOf(range_nextIndex_0));
/* 108 */     range_numElementsTodo_0  = startToEnd.divide(step).longValue();
/* 109 */     if (range_numElementsTodo_0 < 0) {
/* 110 */       range_numElementsTodo_0 = 0;
/* 111 */     } else if (startToEnd.remainder(step).compareTo(java.math.BigInteger.valueOf(0L)) != 0) {
/* 112 */       range_numElementsTodo_0++;
/* 113 */     }
/* 114 */   }
/* 115 */
/* 116 */   private void agg_doConsume_0(long agg_expr_0_0) throws java.io.IOException {
/* 117 */     // do aggregate
/* 118 */     // common sub-expressions
/* 119 */
/* 120 */     // evaluate aggregate functions and update aggregation buffers
/* 121 */
/* 122 */     agg_agg_isNull_2_0 = true;
/* 123 */     long agg_value_2 = -1L;
/* 124 */
/* 125 */     if (!agg_bufIsNull_0 && (agg_agg_isNull_2_0 ||
/* 126 */         agg_value_2 > agg_bufValue_0)) {
/* 127 */       agg_agg_isNull_2_0 = false;
/* 128 */       agg_value_2 = agg_bufValue_0;
/* 129 */     }
/* 130 */
/* 131 */     if (!false && (agg_agg_isNull_2_0 ||
/* 132 */         agg_value_2 > agg_expr_0_0)) {
/* 133 */       agg_agg_isNull_2_0 = false;
/* 134 */       agg_value_2 = agg_expr_0_0;
/* 135 */     }
/* 136 */
/* 137 */     agg_bufIsNull_0 = agg_agg_isNull_2_0;
/* 138 */     agg_bufValue_0 = agg_value_2;
/* 139 */
/* 140 */   }
/* 141 */
/* 142 */   protected void processNext() throws java.io.IOException {
/* 143 */     while (!agg_initAgg_0) {
/* 144 */       agg_initAgg_0 = true;
/* 145 */       long agg_beforeAgg_0 = System.nanoTime();
/* 146 */       agg_doAggregateWithoutKey_0();
/* 147 */       ((org.apache.spark.sql.execution.metric.SQLMetric) references[2] /* aggTime */).add((System.nanoTime() - agg_beforeAgg_0) / 1000000);
/* 148 */
/* 149 */       // output the result
/* 150 */
/* 151 */       ((org.apache.spark.sql.execution.metric.SQLMetric) references[1] /* numOutputRows */).add(1);
/* 152 */       range_mutableStateArray_0[2].reset();
/* 153 */
/* 154 */       range_mutableStateArray_0[2].zeroOutNullBytes();
/* 155 */
/* 156 */       if (agg_bufIsNull_0) {
/* 157 */         range_mutableStateArray_0[2].setNullAt(0);
/* 158 */       } else {
/* 159 */         range_mutableStateArray_0[2].write(0, agg_bufValue_0);
/* 160 */       }
/* 161 */       append((range_mutableStateArray_0[2].getRow()));
/* 162 */     }
/* 163 */   }
/* 164 */
/* 165 */ }
```

### Why are the changes needed?

For better debuggability.

### Does this PR introduce _any_ user-facing change?

Yes. After this change, users can see subquery code by `EXPLAIN CODEGEN`.

### How was this patch tested?

New test.

Closes apache#30859 from sarutak/explain-codegen-subqueries.

Authored-by: Kousuke Saruta <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>
(cherry picked from commit f4e1069)
Signed-off-by: Dongjoon Hyun <[email protected]>
HyukjinKwon pushed a commit that referenced this pull request Jan 12, 2021
…subquery code

### What changes were proposed in this pull request?

This PR fixes an issue that `EXPLAIN CODEGEN` and `BenchmarkQueryTest` don't show the corresponding code for subqueries.

The following example is about `EXPLAIN CODEGEN`.
```
spark.conf.set("spark.sql.adaptive.enabled", "false")
val df = spark.range(1, 100)
df.createTempView("df")
spark.sql("SELECT (SELECT min(id) AS v FROM df)").explain("CODEGEN")

scala> spark.sql("SELECT (SELECT min(id) AS v FROM df)").explain("CODEGEN")
Found 1 WholeStageCodegen subtrees.
== Subtree 1 / 1 (maxMethodCodeSize:55; maxConstantPoolSize:97(0.15% used); numInnerClasses:0) ==
*(1) Project [Subquery scalar-subquery#3, [id=#24] AS scalarsubquery()#5L]
:  +- Subquery scalar-subquery#3, [id=#24]
:     +- *(2) HashAggregate(keys=[], functions=[min(id#0L)], output=[v#2L])
:        +- Exchange SinglePartition, ENSURE_REQUIREMENTS, [id=#20]
:           +- *(1) HashAggregate(keys=[], functions=[partial_min(id#0L)], output=[min#8L])
:              +- *(1) Range (1, 100, step=1, splits=12)
+- *(1) Scan OneRowRelation[]

Generated code:
/* 001 */ public Object generate(Object[] references) {
/* 002 */   return new GeneratedIteratorForCodegenStage1(references);
/* 003 */ }
/* 004 */
/* 005 */ // codegenStageId=1
/* 006 */ final class GeneratedIteratorForCodegenStage1 extends org.apache.spark.sql.execution.BufferedRowIterator {
/* 007 */   private Object[] references;
/* 008 */   private scala.collection.Iterator[] inputs;
/* 009 */   private scala.collection.Iterator rdd_input_0;
/* 010 */   private org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter[] project_mutableStateArray_0 = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter[1];
/* 011 */
/* 012 */   public GeneratedIteratorForCodegenStage1(Object[] references) {
/* 013 */     this.references = references;
/* 014 */   }
/* 015 */
/* 016 */   public void init(int index, scala.collection.Iterator[] inputs) {
/* 017 */     partitionIndex = index;
/* 018 */     this.inputs = inputs;
/* 019 */     rdd_input_0 = inputs[0];
/* 020 */     project_mutableStateArray_0[0] = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter(1, 0);
/* 021 */
/* 022 */   }
/* 023 */
/* 024 */   private void project_doConsume_0() throws java.io.IOException {
/* 025 */     // common sub-expressions
/* 026 */
/* 027 */     project_mutableStateArray_0[0].reset();
/* 028 */
/* 029 */     if (false) {
/* 030 */       project_mutableStateArray_0[0].setNullAt(0);
/* 031 */     } else {
/* 032 */       project_mutableStateArray_0[0].write(0, 1L);
/* 033 */     }
/* 034 */     append((project_mutableStateArray_0[0].getRow()));
/* 035 */
/* 036 */   }
/* 037 */
/* 038 */   protected void processNext() throws java.io.IOException {
/* 039 */     while ( rdd_input_0.hasNext()) {
/* 040 */       InternalRow rdd_row_0 = (InternalRow) rdd_input_0.next();
/* 041 */       ((org.apache.spark.sql.execution.metric.SQLMetric) references[0] /* numOutputRows */).add(1);
/* 042 */       project_doConsume_0();
/* 043 */       if (shouldStop()) return;
/* 044 */     }
/* 045 */   }
/* 046 */
/* 047 */ }
```

After this change, the corresponding code for subqueries are shown.
```
Found 3 WholeStageCodegen subtrees.
== Subtree 1 / 3 (maxMethodCodeSize:282; maxConstantPoolSize:206(0.31% used); numInnerClasses:0) ==
*(1) HashAggregate(keys=[], functions=[partial_min(id#0L)], output=[min#8L])
+- *(1) Range (1, 100, step=1, splits=12)

Generated code:
/* 001 */ public Object generate(Object[] references) {
/* 002 */   return new GeneratedIteratorForCodegenStage1(references);
/* 003 */ }
/* 004 */
/* 005 */ // codegenStageId=1
/* 006 */ final class GeneratedIteratorForCodegenStage1 extends org.apache.spark.sql.execution.BufferedRowIterator {
/* 007 */   private Object[] references;
/* 008 */   private scala.collection.Iterator[] inputs;
/* 009 */   private boolean agg_initAgg_0;
/* 010 */   private boolean agg_bufIsNull_0;
/* 011 */   private long agg_bufValue_0;
/* 012 */   private boolean range_initRange_0;
/* 013 */   private long range_nextIndex_0;
/* 014 */   private TaskContext range_taskContext_0;
/* 015 */   private InputMetrics range_inputMetrics_0;
/* 016 */   private long range_batchEnd_0;
/* 017 */   private long range_numElementsTodo_0;
/* 018 */   private boolean agg_agg_isNull_2_0;
/* 019 */   private org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter[] range_mutableStateArray_0 = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter[3];
/* 020 */
/* 021 */   public GeneratedIteratorForCodegenStage1(Object[] references) {
/* 022 */     this.references = references;
/* 023 */   }
/* 024 */
/* 025 */   public void init(int index, scala.collection.Iterator[] inputs) {
/* 026 */     partitionIndex = index;
/* 027 */     this.inputs = inputs;
/* 028 */
/* 029 */     range_taskContext_0 = TaskContext.get();
/* 030 */     range_inputMetrics_0 = range_taskContext_0.taskMetrics().inputMetrics();
/* 031 */     range_mutableStateArray_0[0] = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter(1, 0);
/* 032 */     range_mutableStateArray_0[1] = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter(1, 0);
/* 033 */     range_mutableStateArray_0[2] = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter(1, 0);
/* 034 */
/* 035 */   }
/* 036 */
/* 037 */   private void agg_doAggregateWithoutKey_0() throws java.io.IOException {
/* 038 */     // initialize aggregation buffer
/* 039 */     agg_bufIsNull_0 = true;
/* 040 */     agg_bufValue_0 = -1L;
/* 041 */
/* 042 */     // initialize Range
/* 043 */     if (!range_initRange_0) {
/* 044 */       range_initRange_0 = true;
/* 045 */       initRange(partitionIndex);
/* 046 */     }
/* 047 */
/* 048 */     while (true) {
/* 049 */       if (range_nextIndex_0 == range_batchEnd_0) {
/* 050 */         long range_nextBatchTodo_0;
/* 051 */         if (range_numElementsTodo_0 > 1000L) {
/* 052 */           range_nextBatchTodo_0 = 1000L;
/* 053 */           range_numElementsTodo_0 -= 1000L;
/* 054 */         } else {
/* 055 */           range_nextBatchTodo_0 = range_numElementsTodo_0;
/* 056 */           range_numElementsTodo_0 = 0;
/* 057 */           if (range_nextBatchTodo_0 == 0) break;
/* 058 */         }
/* 059 */         range_batchEnd_0 += range_nextBatchTodo_0 * 1L;
/* 060 */       }
/* 061 */
/* 062 */       int range_localEnd_0 = (int)((range_batchEnd_0 - range_nextIndex_0) / 1L);
/* 063 */       for (int range_localIdx_0 = 0; range_localIdx_0 < range_localEnd_0; range_localIdx_0++) {
/* 064 */         long range_value_0 = ((long)range_localIdx_0 * 1L) + range_nextIndex_0;
/* 065 */
/* 066 */         agg_doConsume_0(range_value_0);
/* 067 */
/* 068 */         // shouldStop check is eliminated
/* 069 */       }
/* 070 */       range_nextIndex_0 = range_batchEnd_0;
/* 071 */       ((org.apache.spark.sql.execution.metric.SQLMetric) references[0] /* numOutputRows */).add(range_localEnd_0);
/* 072 */       range_inputMetrics_0.incRecordsRead(range_localEnd_0);
/* 073 */       range_taskContext_0.killTaskIfInterrupted();
/* 074 */     }
/* 075 */
/* 076 */   }
/* 077 */
/* 078 */   private void initRange(int idx) {
/* 079 */     java.math.BigInteger index = java.math.BigInteger.valueOf(idx);
/* 080 */     java.math.BigInteger numSlice = java.math.BigInteger.valueOf(12L);
/* 081 */     java.math.BigInteger numElement = java.math.BigInteger.valueOf(99L);
/* 082 */     java.math.BigInteger step = java.math.BigInteger.valueOf(1L);
/* 083 */     java.math.BigInteger start = java.math.BigInteger.valueOf(1L);
/* 084 */     long partitionEnd;
/* 085 */
/* 086 */     java.math.BigInteger st = index.multiply(numElement).divide(numSlice).multiply(step).add(start);
/* 087 */     if (st.compareTo(java.math.BigInteger.valueOf(Long.MAX_VALUE)) > 0) {
/* 088 */       range_nextIndex_0 = Long.MAX_VALUE;
/* 089 */     } else if (st.compareTo(java.math.BigInteger.valueOf(Long.MIN_VALUE)) < 0) {
/* 090 */       range_nextIndex_0 = Long.MIN_VALUE;
/* 091 */     } else {
/* 092 */       range_nextIndex_0 = st.longValue();
/* 093 */     }
/* 094 */     range_batchEnd_0 = range_nextIndex_0;
/* 095 */
/* 096 */     java.math.BigInteger end = index.add(java.math.BigInteger.ONE).multiply(numElement).divide(numSlice)
/* 097 */     .multiply(step).add(start);
/* 098 */     if (end.compareTo(java.math.BigInteger.valueOf(Long.MAX_VALUE)) > 0) {
/* 099 */       partitionEnd = Long.MAX_VALUE;
/* 100 */     } else if (end.compareTo(java.math.BigInteger.valueOf(Long.MIN_VALUE)) < 0) {
/* 101 */       partitionEnd = Long.MIN_VALUE;
/* 102 */     } else {
/* 103 */       partitionEnd = end.longValue();
/* 104 */     }
/* 105 */
/* 106 */     java.math.BigInteger startToEnd = java.math.BigInteger.valueOf(partitionEnd).subtract(
/* 107 */       java.math.BigInteger.valueOf(range_nextIndex_0));
/* 108 */     range_numElementsTodo_0  = startToEnd.divide(step).longValue();
/* 109 */     if (range_numElementsTodo_0 < 0) {
/* 110 */       range_numElementsTodo_0 = 0;
/* 111 */     } else if (startToEnd.remainder(step).compareTo(java.math.BigInteger.valueOf(0L)) != 0) {
/* 112 */       range_numElementsTodo_0++;
/* 113 */     }
/* 114 */   }
/* 115 */
/* 116 */   private void agg_doConsume_0(long agg_expr_0_0) throws java.io.IOException {
/* 117 */     // do aggregate
/* 118 */     // common sub-expressions
/* 119 */
/* 120 */     // evaluate aggregate functions and update aggregation buffers
/* 121 */
/* 122 */     agg_agg_isNull_2_0 = true;
/* 123 */     long agg_value_2 = -1L;
/* 124 */
/* 125 */     if (!agg_bufIsNull_0 && (agg_agg_isNull_2_0 ||
/* 126 */         agg_value_2 > agg_bufValue_0)) {
/* 127 */       agg_agg_isNull_2_0 = false;
/* 128 */       agg_value_2 = agg_bufValue_0;
/* 129 */     }
/* 130 */
/* 131 */     if (!false && (agg_agg_isNull_2_0 ||
/* 132 */         agg_value_2 > agg_expr_0_0)) {
/* 133 */       agg_agg_isNull_2_0 = false;
/* 134 */       agg_value_2 = agg_expr_0_0;
/* 135 */     }
/* 136 */
/* 137 */     agg_bufIsNull_0 = agg_agg_isNull_2_0;
/* 138 */     agg_bufValue_0 = agg_value_2;
/* 139 */
/* 140 */   }
/* 141 */
/* 142 */   protected void processNext() throws java.io.IOException {
/* 143 */     while (!agg_initAgg_0) {
/* 144 */       agg_initAgg_0 = true;
/* 145 */       long agg_beforeAgg_0 = System.nanoTime();
/* 146 */       agg_doAggregateWithoutKey_0();
/* 147 */       ((org.apache.spark.sql.execution.metric.SQLMetric) references[2] /* aggTime */).add((System.nanoTime() - agg_beforeAgg_0) / 1000000);
/* 148 */
/* 149 */       // output the result
/* 150 */
/* 151 */       ((org.apache.spark.sql.execution.metric.SQLMetric) references[1] /* numOutputRows */).add(1);
/* 152 */       range_mutableStateArray_0[2].reset();
/* 153 */
/* 154 */       range_mutableStateArray_0[2].zeroOutNullBytes();
/* 155 */
/* 156 */       if (agg_bufIsNull_0) {
/* 157 */         range_mutableStateArray_0[2].setNullAt(0);
/* 158 */       } else {
/* 159 */         range_mutableStateArray_0[2].write(0, agg_bufValue_0);
/* 160 */       }
/* 161 */       append((range_mutableStateArray_0[2].getRow()));
/* 162 */     }
/* 163 */   }
/* 164 */
/* 165 */ }
```

### Why are the changes needed?

For better debuggability.

### Does this PR introduce _any_ user-facing change?

Yes. After this change, users can see subquery code by `EXPLAIN CODEGEN`.

### How was this patch tested?

New test.

Closes apache#30859 from sarutak/explain-codegen-subqueries.

Authored-by: Kousuke Saruta <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>
(cherry picked from commit f4e1069)
Signed-off-by: Dongjoon Hyun <[email protected]>
HyukjinKwon pushed a commit that referenced this pull request Feb 3, 2025
This is a trivial change to replace the loop index from `int` to `long`. Surprisingly, microbenchmark shows more than double performance uplift.

Analysis
--------
The hot loop of `arrayEquals` method is simplifed as below. Loop index `i` is defined as `int`, it's compared with `length`, which is a `long`, to determine if the loop should end.
```
public static boolean arrayEquals(
    Object leftBase, long leftOffset, Object rightBase, long rightOffset, final long length) {
  ......
  int i = 0;
  while (i <= length - 8) {
    if (Platform.getLong(leftBase, leftOffset + i) !=
        Platform.getLong(rightBase, rightOffset + i)) {
          return false;
    }
    i += 8;
  }
  ......
}
```

Strictly speaking, there's a code bug here. If `length` is greater than 2^31 + 8, this loop will never end because `i` as a 32 bit integer is at most 2^31 - 1. But compiler must consider this behaviour as intentional and generate code strictly match the logic. It prevents compiler from generating optimal code.

Defining loop index `i` as `long` corrects this issue. Besides more accurate code logic, JIT is able to optimize this code much more aggressively. From microbenchmark, this trivial change improves performance significantly on both Arm and x86 platforms.

Benchmark
---------
Source code:
https://gist.github.com/cyb70289/258e261f388e22f47e4d961431786d1a

Result on Arm Neoverse N2:
```
Benchmark                             Mode  Cnt    Score   Error  Units
ArrayEqualsBenchmark.arrayEqualsInt   avgt   10  674.313 ± 0.213  ns/op
ArrayEqualsBenchmark.arrayEqualsLong  avgt   10  313.563 ± 2.338  ns/op
```

Result on Intel Cascake Lake:
```
Benchmark                             Mode  Cnt     Score   Error  Units
ArrayEqualsBenchmark.arrayEqualsInt   avgt   10  1130.695 ± 0.168  ns/op
ArrayEqualsBenchmark.arrayEqualsLong  avgt   10   461.979 ± 0.097  ns/op
```

Deep dive
---------
Dive deep to the machine code level, we can see why the big gap. Listed below are arm64 assembly generated by Openjdk-17 C2 compiler.

For `int i`, the machine code is similar to source code, no deep optimization. Safepoint polling is expensive in this short loop.
```
// jit c2 machine code snippet
  0x0000ffff81ba8904:   mov        w15, wzr              // int i = 0
  0x0000ffff81ba8908:   nop
  0x0000ffff81ba890c:   nop
loop:
  0x0000ffff81ba8910:   ldr        x10, [x13, w15, sxtw] // Platform.getLong(leftBase, leftOffset + i)
  0x0000ffff81ba8914:   ldr        x14, [x12, w15, sxtw] // Platform.getLong(rightBase, rightOffset + i)
  0x0000ffff81ba8918:   cmp        x10, x14
  0x0000ffff81ba891c:   b.ne       0x0000ffff81ba899c    // return false if not equal
  0x0000ffff81ba8920:   ldr        x14, [x28, apache#848]      // x14 -> safepoint
  0x0000ffff81ba8924:   add        w15, w15, #0x8        // i += 8
  0x0000ffff81ba8928:   ldr        wzr, [x14]            // safepoint polling
  0x0000ffff81ba892c:   sxtw       x10, w15              // extend i to long
  0x0000ffff81ba8930:   cmp        x10, x11
  0x0000ffff81ba8934:   b.le       0x0000ffff81ba8910    // if (i <= length - 8) goto loop
```

For `long i`, JIT is able to do much more aggressive optimization. E.g, below code snippet unrolls the loop by four.
```
// jit c2 machine code snippet
unrolled_loop:
  0x0000ffff91de6fe0:   sxtw       x10, w7
  0x0000ffff91de6fe4:   add        x23, x22, x10
  0x0000ffff91de6fe8:   add        x24, x21, x10
  0x0000ffff91de6fec:   ldr        x13, [x23]          // unroll-1
  0x0000ffff91de6ff0:   ldr        x14, [x24]
  0x0000ffff91de6ff4:   cmp        x13, x14
  0x0000ffff91de6ff8:   b.ne       0x0000ffff91de70a8
  0x0000ffff91de6ffc:   ldr        x13, [x23, #8]      // unroll-2
  0x0000ffff91de7000:   ldr        x14, [x24, #8]
  0x0000ffff91de7004:   cmp        x13, x14
  0x0000ffff91de7008:   b.ne       0x0000ffff91de70b4
  0x0000ffff91de700c:   ldr        x13, [x23, #16]     // unroll-3
  0x0000ffff91de7010:   ldr        x14, [x24, #16]
  0x0000ffff91de7014:   cmp        x13, x14
  0x0000ffff91de7018:   b.ne       0x0000ffff91de70a4
  0x0000ffff91de701c:   ldr        x13, [x23, #24]     // unroll-4
  0x0000ffff91de7020:   ldr        x14, [x24, #24]
  0x0000ffff91de7024:   cmp        x13, x14
  0x0000ffff91de7028:   b.ne       0x0000ffff91de70b0
  0x0000ffff91de702c:   add        w7, w7, #0x20
  0x0000ffff91de7030:   cmp        w7, w11
  0x0000ffff91de7034:   b.lt       0x0000ffff91de6fe0
```

### What changes were proposed in this pull request?

A trivial change to replace loop index `i` of method `arrayEquals` from `int` to `long`.

### Why are the changes needed?

To improve performance and fix a possible bug.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Existing unit tests.

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes apache#49568 from cyb70289/arrayEquals.

Authored-by: Yibo Cai <[email protected]>
Signed-off-by: Sean Owen <[email protected]>
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2 participants