本文基于 SPARK 3.3.0
从一个unit test来探究SPARK Codegen的逻辑,
test("SortAggregate should be included in WholeStageCodegen") {
val df = spark.range(10).agg(max(col("id")), avg(col("id")))
withSQLConf("spark.sql.test.forceApplySortAggregate" -> "true") {
val plan = df.queryExecution.executedPlan
assert(plan.exists(p =>
p.isInstanceOf[WholeStageCodegenExec] &&
p.asInstanceOf[WholeStageCodegenExec].child.isInstanceOf[SortAggregateExec]))
assert(df.collect() === Array(Row(9, 4.5)))
}
}
该sql形成的执行计划第一部分的全代码生成部分如下:
WholeStageCodegen
± *(1) SortAggregate(key=[], functions=[partial_max(id#0L), partial_avg(id#0L)], output=[max#12L, sum#13, count#14L])
± *(1) Range (0, 10, step=1, splits=2)
第一阶段的代码生成涉及到SortAggregateExec和RangeExec的produce和consume方法,这里一一来分析:
第一阶段wholeStageCodegen数据流如下:
WholeStageCodegenExec SortAggregateExec(partial) RangeExec
=========================================================================
-> execute()
|
doExecute() ---------> inputRDDs() -----------------> inputRDDs()
|
doCodeGen()
|
+-----------------> produce()
|
doProduce()
|
doProduceWithoutKeys() -------> produce()
|
doProduce()
|
doConsume()<------------------- consume()
|
doConsumeWithoutKeys()
|并不是doConsumeWithoutKeys调用consume,而是由doProduceWithoutKeys调用
doConsume() <-------- consume()
doProduce最终调用方法doProduceWithoutKeys,该部分代码如下:
private def doProduceWithoutKeys(ctx: CodegenContext): String = {
val initAgg = ctx.addMutableState(CodeGenerator.JAVA_BOOLEAN, "initAgg")
// The generated function doesn't have input row in the code context.
ctx.INPUT_ROW = null
// generate variables for aggregation buffer
val functions = aggregateExpressions.map(_.aggregateFunction.asInstanceOf[DeclarativeAggregate])
val initExpr = functions.map(f => f.initialValues)
bufVars = initExpr.map { exprs =>
exprs.map { e =>
val isNull = ctx.addMutableState(CodeGenerator.JAVA_BOOLEAN, "bufIsNull")
val value = ctx.addMutableState(CodeGenerator.javaType(e.dataType), "bufValue")
// The initial expression should not access any column
val ev = e.genCode(ctx)
val initVars =
code"""
|$isNull = ${ev.isNull};
|$value = ${ev.value};
""".stripMargin
ExprCode(
ev.code + initVars,
JavaCode.isNullGlobal(isNull),
JavaCode.global(value, e.dataType))
}
}
val flatBufVars = bufVars.flatten
val initBufVar = evaluateVariables(flatBufVars)
// generate variables for output
val (resultVars, genResult) = if (modes.contains(Final) || modes.contains(Complete)) {
// evaluate aggregate results
ctx.currentVars = flatBufVars
val aggResults = bindReferences(
functions.map(_.evaluateExpression),
aggregateBufferAttributes).map(_.genCode(ctx))
println(s"aggResults: ${aggResults}")
val evaluateAggResults = evaluateVariables(aggResults)
// evaluate result expressions
ctx.currentVars = aggResults
val resultVars = bindReferences(resultExpressions, aggregateAttributes).map(_.genCode(ctx))
(resultVars,
s"""
|$evaluateAggResults
|${evaluateVariables(resultVars)}
""".stripMargin)
} else if (modes.contains(Partial) || modes.contains(PartialMerge)) {
// output the aggregate buffer directly
(flatBufVars, "")
} else {
// no aggregate function, the result should be literals
val resultVars = resultExpressions.map(_.genCode(ctx))
(resultVars, evaluateVariables(resultVars))
}
val doAgg = ctx.freshName("doAggregateWithoutKey")
val doAggFuncName = ctx.addNewFunction(doAgg,
s"""
|private void $doAgg() throws java.io.IOException {
| // initialize aggregation buffer
| $initBufVar
|
| ${child.asInstanceOf[CodegenSupport].produce(ctx, this)}
|}
""".stripMargin)
val numOutput = metricTerm(ctx, "numOutputRows")
val doAggWithRecordMetric =
if (needHashTable) {
val aggTime = metricTerm(ctx, "aggTime")
val beforeAgg = ctx.freshName("beforeAgg")
s"""
|long $beforeAgg = System.nanoTime();
|$doAggFuncName();
|$aggTime.add((System.nanoTime() - $beforeAgg) / $NANOS_PER_MILLIS);
""".stripMargin
} else {
s"$doAggFuncName();"
}
s"""
|while (!$initAgg) {
| $initAgg = true;
| $doAggWithRecordMetric
|
| // output the result
| ${genResult.trim}
|
| $numOutput.add(1);
| ${consume(ctx, resultVars).trim}
|}
""".stripMargin
}
val initAgg = ctx.addMutableState(CodeGenerator.JAVA_BOOLEAN, “initAgg”)
用来进行初始化聚合的判断,便于只进行一次代码生成
ctx.INPUT_ROW = null
这里把INPUT_ROW设置为null的原因是来判断BoundReference绑定的值是否来自于InternalRow类型的变量,这样的话,就得调用InternalRow对应的方法获取对应的值,如getLong方法。
这里设置为null,说明不是来自于InternalRow类型的变量(也就是计算的值大概率不是来自于其他算子的计算结果),也就是直接赋值。
val functions = aggregateExpressions.map(_.aggregateFunction.asInstanceOf[DeclarativeAggregate])
对于这一句为什么 aggregateFunction一定是DeclarativeAggregate类型呢?为什么不是ImperativeAggregate类型的呢?
其实因为是ImperativeAggregate是继承自CodegenFallback的,这在CollapseCodegenStages规则中supportCodegen方法中就会进行判断不符合全代码生成的条件,自然就不会有代码生成这一步,所以aggregateFunction只能是DeclarativeAggregate类型的。
val initExpr = functions.map(f => f.initialValues)
这个是聚合函数的初始值,对于avg来说则是 Seq( /* sum = */ Literal.default(sumDataType),/* count = */ Literal(0L))
,如没特别说明,我们就只讲解AVG的代码生成部分,因为MAX等表达式原理是一样的。(AVG则是由SUM和COUNT两个缓冲值组成)
bufVars = …
这是一个赋值操作,其中ctx.addMutableState()操作则是声明变量,这里的变量属于全局变量,也就是类的成员变量,前缀是当前类的前缀,具体是在CodegenSupport的
variablePrefix方法中,对于SortAggregateExec则对应为sortAgg,通过该方法会在对应的生成类中,生成如下的成员变量:
//对应于sum
private boolean sortAgg_bufIsNull_0;
private long sortAgg_bufValue_0;
//对应于count
private boolean sortAgg_bufIsNull_1;
private long sortAgg_bufValue_1;
initVars=这部分则是根据聚合函数的初始值的代码生成部分,初始化成员变量sortAgg_bufIsNull_0,sortAgg_bufValue_0等值,具体的初始化的部分是在下面
其中为什么有IsNull参数?是因为如果说该参数为NULL的话,代码生成的时候就得去判断是否为null,否则就会出现异常。
initBufVar=
这部分代码是上面提到的初始化类的成员变量,具体在哪里初始化呢? 是在聚合函数的一开始,如下:
private void sortAgg_doAggregateWithoutKey_0() throws java.io.IOException {
// initialize aggregation buffer
sortAgg_bufIsNull_0 = true;
sortAgg_bufValue_0 = -1L;
val (resultVars, genResult) =
这部分会根据是部分聚合(Partial)还是最终的聚合(Final)来进行分之判断:
所有对应到Partial则是 (flatBufVars, “”),所以这部分直接把SUM和COUNT(属于AVG的计算缓存)赋值给了resultVars, genResult则是为空,因为不需要做任何处理。
val doAggFuncName =
这部分调用RangExec的produce方法生成代码,而且对于initBufVar的初始化代码也在这里。
val numOutput = metricTerm(ctx, “numOutputRows”)和val doAggWithRecordMetric =
这里会调用metricTerm方法,从而创建指标,这些指标变量会以方法参数形式传递给*WholeStageCodegenExec中的clazz.generate(references).*方法
组装代码
最后一步:*while (!$initAgg) * 是组装代码
doAggWithRecordMetric 是调用child.produce.
genResult.trim 因为这里是Partial Aggregate,所以为空.
numOutput.add(1) 是对输出的记录数加一
consume(ctx, resultVars).trirm 是对输出的数据进行组装,组装成UnsafeRow以便spark进行的后续处理,也就是在此以后返回的数据就是正常的InteralRow的处理方式了,对于consume()
这部分代码我们后续再说,在这里我们先按照数据流的方式来解释代码。
第一阶段wholeStageCodegen生成的代码如下:
/* 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 sortAgg_initAgg_0;
/* 010 */ private boolean sortAgg_bufIsNull_0;
/* 011 */ private long sortAgg_bufValue_0;
/* 012 */ private boolean sortAgg_bufIsNull_1;
/* 013 */ private double sortAgg_bufValue_1;
/* 014 */ private boolean sortAgg_bufIsNull_2;
/* 015 */ private long sortAgg_bufValue_2;
/* 016 */ private boolean range_initRange_0;
/* 017 */ private long range_nextIndex_0;
/* 018 */ private TaskContext range_taskContext_0;
/* 019 */ private InputMetrics range_inputMetrics_0;
/* 020 */ private long range_batchEnd_0;
/* 021 */ private long range_numElementsTodo_0;
/* 022 */ private boolean sortAgg_sortAgg_isNull_4_0;
/* 023 */ private boolean sortAgg_sortAgg_isNull_9_0;
/* 024 */ private org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter[] range_mutableStateArray_0 = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter[3];
/* 025 */
/* 026 */ public GeneratedIteratorForCodegenStage1(Object[] references) {
/* 027 */ this.references = references;
/* 028 */ }
/* 029 */
/* 030 */ public void init(int index, scala.collection.Iterator[] inputs) {
/* 031 */ partitionIndex = index;
/* 032 */ this.inputs = inputs;
/* 033 */
/* 034 */ range_taskContext_0 = TaskContext.get();
/* 035 */ range_inputMetrics_0 = range_taskContext_0.taskMetrics().inputMetrics();
/* 036 */ range_mutableStateArray_0[0] = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter(1, 0);
/* 037 */ range_mutableStateArray_0[1] = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter(1, 0);
/* 038 */ range_mutableStateArray_0[2] = new org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter(3, 0);
/* 039 */
/* 040 */ }
/* 041 */
/* 042 */ private void sortAgg_doAggregate_max_0(long sortAgg_expr_0_0) throws java.io.IOException {
/* 043 */ sortAgg_sortAgg_isNull_4_0 = true;
/* 044 */ long sortAgg_value_4 = -1L;
/* 045 */
/* 046 */ if (!sortAgg_bufIsNull_0 && (sortAgg_sortAgg_isNull_4_0 ||
/* 047 */ sortAgg_bufValue_0 > sortAgg_value_4)) {
/* 048 */ sortAgg_sortAgg_isNull_4_0 = false;
/* 049 */ sortAgg_value_4 = sortAgg_bufValue_0;
/* 050 */ }
/* 051 */
/* 052 */ if (!false && (sortAgg_sortAgg_isNull_4_0 ||
/* 053 */ sortAgg_expr_0_0 > sortAgg_value_4)) {
/* 054 */ sortAgg_sortAgg_isNull_4_0 = false;
/* 055 */ sortAgg_value_4 = sortAgg_expr_0_0;
/* 056 */ }
/* 057 */
/* 058 */ sortAgg_bufIsNull_0 = sortAgg_sortAgg_isNull_4_0;
/* 059 */ sortAgg_bufValue_0 = sortAgg_value_4;
/* 060 */ }
/* 061 */
/* 062 */ private void sortAgg_doAggregateWithoutKey_0() throws java.io.IOException {
/* 063 */ // initialize aggregation buffer
/* 064 */ sortAgg_bufIsNull_0 = true;
/* 065 */ sortAgg_bufValue_0 = -1L;
/* 066 */ sortAgg_bufIsNull_1 = false;
/* 067 */ sortAgg_bufValue_1 = 0.0D;
/* 068 */ sortAgg_bufIsNull_2 = false;
/* 069 */ sortAgg_bufValue_2 = 0L;
/* 070 */
/* 071 */ // initialize Range
/* 072 */ if (!range_initRange_0) {
/* 073 */ range_initRange_0 = true;
/* 074 */ initRange(partitionIndex);
/* 075 */ }
/* 076 */
/* 077 */ while (true) {
/* 078 */ if (range_nextIndex_0 == range_batchEnd_0) {
/* 079 */ long range_nextBatchTodo_0;
/* 080 */ if (range_numElementsTodo_0 > 1000L) {
/* 081 */ range_nextBatchTodo_0 = 1000L;
/* 082 */ range_numElementsTodo_0 -= 1000L;
/* 083 */ } else {
/* 084 */ range_nextBatchTodo_0 = range_numElementsTodo_0;
/* 085 */ range_numElementsTodo_0 = 0;
/* 086 */ if (range_nextBatchTodo_0 == 0) break;
/* 087 */ }
/* 088 */ range_batchEnd_0 += range_nextBatchTodo_0 * 1L;
/* 089 */ }
/* 090 */
/* 091 */ int range_localEnd_0 = (int)((range_batchEnd_0 - range_nextIndex_0) / 1L);
/* 092 */ for (int range_localIdx_0 = 0; range_localIdx_0 < range_localEnd_0; range_localIdx_0++) {
/* 093 */ long range_value_0 = ((long)range_localIdx_0 * 1L) + range_nextIndex_0;
/* 094 */
/* 095 */ sortAgg_doConsume_0(range_value_0);
/* 096 */
/* 097 */ // shouldStop check is eliminated
/* 098 */ }
/* 099 */ range_nextIndex_0 = range_batchEnd_0;
/* 100 */ ((org.apache.spark.sql.execution.metric.SQLMetric) references[0] /* numOutputRows */).add(range_localEnd_0);
/* 101 */ range_inputMetrics_0.incRecordsRead(range_localEnd_0);
/* 102 */ range_taskContext_0.killTaskIfInterrupted();
/* 103 */ }
/* 104 */
/* 105 */ }
/* 106 */
/* 107 */ private void initRange(int idx) {
/* 108 */ java.math.BigInteger index = java.math.BigInteger.valueOf(idx);
/* 109 */ java.math.BigInteger numSlice = java.math.BigInteger.valueOf(2L);
/* 110 */ java.math.BigInteger numElement = java.math.BigInteger.valueOf(10L);
/* 111 */ java.math.BigInteger step = java.math.BigInteger.valueOf(1L);
/* 112 */ java.math.BigInteger start = java.math.BigInteger.valueOf(0L);
/* 113 */ long partitionEnd;
/* 114 */
/* 115 */ java.math.BigInteger st = index.multiply(numElement).divide(numSlice).multiply(step).add(start);
/* 116 */ if (st.compareTo(java.math.BigInteger.valueOf(Long.MAX_VALUE)) > 0) {
/* 117 */ range_nextIndex_0 = Long.MAX_VALUE;
/* 118 */ } else if (st.compareTo(java.math.BigInteger.valueOf(Long.MIN_VALUE)) < 0) {
/* 119 */ range_nextIndex_0 = Long.MIN_VALUE;
/* 120 */ } else {
/* 121 */ range_nextIndex_0 = st.longValue();
/* 122 */ }
/* 123 */ range_batchEnd_0 = range_nextIndex_0;
/* 124 */
/* 125 */ java.math.BigInteger end = index.add(java.math.BigInteger.ONE).multiply(numElement).divide(numSlice)
/* 126 */ .multiply(step).add(start);
/* 127 */ if (end.compareTo(java.math.BigInteger.valueOf(Long.MAX_VALUE)) > 0) {
/* 128 */ partitionEnd = Long.MAX_VALUE;
/* 129 */ } else if (end.compareTo(java.math.BigInteger.valueOf(Long.MIN_VALUE)) < 0) {
/* 130 */ partitionEnd = Long.MIN_VALUE;
/* 131 */ } else {
/* 132 */ partitionEnd = end.longValue();
/* 133 */ }
/* 134 */
/* 135 */ java.math.BigInteger startToEnd = java.math.BigInteger.valueOf(partitionEnd).subtract(
/* 136 */ java.math.BigInteger.valueOf(range_nextIndex_0));
/* 137 */ range_numElementsTodo_0 = startToEnd.divide(step).longValue();
/* 138 */ if (range_numElementsTodo_0 < 0) {
/* 139 */ range_numElementsTodo_0 = 0;
/* 140 */ } else if (startToEnd.remainder(step).compareTo(java.math.BigInteger.valueOf(0L)) != 0) {
/* 141 */ range_numElementsTodo_0++;
/* 142 */ }
/* 143 */ }
/* 144 */
/* 145 */ protected void processNext() throws java.io.IOException {
/* 146 */ while (!sortAgg_initAgg_0) {
/* 147 */ sortAgg_initAgg_0 = true;
/* 148 */ sortAgg_doAggregateWithoutKey_0();
/* 149 */
/* 150 */ // output the result
/* 151 */
/* 152 */ ((org.apache.spark.sql.execution.metric.SQLMetric) references[1] /* numOutputRows */).add(1);
/* 153 */ range_mutableStateArray_0[2].reset();
/* 154 */
/* 155 */ range_mutableStateArray_0[2].zeroOutNullBytes();
/* 156 */
/* 157 */ if (sortAgg_bufIsNull_0) {
/* 158 */ range_mutableStateArray_0[2].setNullAt(0);
/* 159 */ } else {
/* 160 */ range_mutableStateArray_0[2].write(0, sortAgg_bufValue_0);
/* 161 */ }
/* 162 */
/* 163 */ if (sortAgg_bufIsNull_1) {
/* 164 */ range_mutableStateArray_0[2].setNullAt(1);
/* 165 */ } else {
/* 166 */ range_mutableStateArray_0[2].write(1, sortAgg_bufValue_1);
/* 167 */ }
/* 168 */
/* 169 */ if (sortAgg_bufIsNull_2) {
/* 170 */ range_mutableStateArray_0[2].setNullAt(2);
/* 171 */ } else {
/* 172 */ range_mutableStateArray_0[2].write(2, sortAgg_bufValue_2);
/* 173 */ }
/* 174 */ append((range_mutableStateArray_0[2].getRow()));
/* 175 */ }
/* 176 */ }
/* 177 */
/* 178 */ private void sortAgg_doConsume_0(long sortAgg_expr_0_0) throws java.io.IOException {
/* 179 */ // do aggregate
/* 180 */ // common sub-expressions
/* 181 */
/* 182 */ // evaluate aggregate functions and update aggregation buffers
/* 183 */ sortAgg_doAggregate_max_0(sortAgg_expr_0_0);
/* 184 */ sortAgg_doAggregate_avg_0(sortAgg_expr_0_0);
/* 185 */
/* 186 */ }
/* 187 */
/* 188 */ private void sortAgg_doAggregate_avg_0(long sortAgg_expr_0_0) throws java.io.IOException {
/* 189 */ boolean sortAgg_isNull_7 = true;
/* 190 */ double sortAgg_value_7 = -1.0;
/* 191 */
/* 192 */ if (!sortAgg_bufIsNull_1) {
/* 193 */ sortAgg_sortAgg_isNull_9_0 = true;
/* 194 */ double sortAgg_value_9 = -1.0;
/* 195 */ do {
/* 196 */ boolean sortAgg_isNull_10 = false;
/* 197 */ double sortAgg_value_10 = -1.0;
/* 198 */ if (!false) {
/* 199 */ sortAgg_value_10 = (double) sortAgg_expr_0_0;
/* 200 */ }
/* 201 */ if (!sortAgg_isNull_10) {
/* 202 */ sortAgg_sortAgg_isNull_9_0 = false;
/* 203 */ sortAgg_value_9 = sortAgg_value_10;
/* 204 */ continue;
/* 205 */ }
/* 206 */
/* 207 */ if (!false) {
/* 208 */ sortAgg_sortAgg_isNull_9_0 = false;
/* 209 */ sortAgg_value_9 = 0.0D;
/* 210 */ continue;
/* 211 */ }
/* 212 */
/* 213 */ } while (false);
/* 214 */
/* 215 */ sortAgg_isNull_7 = false; // resultCode could change nullability.
/* 216 */
/* 217 */ sortAgg_value_7 = sortAgg_bufValue_1 + sortAgg_value_9;
/* 218 */
/* 219 */ }
/* 220 */ boolean sortAgg_isNull_13 = false;
/* 221 */ long sortAgg_value_13 = -1L;
/* 222 */ if (!false && false) {
/* 223 */ sortAgg_isNull_13 = sortAgg_bufIsNull_2;
/* 224 */ sortAgg_value_13 = sortAgg_bufValue_2;
/* 225 */ } else {
/* 226 */ boolean sortAgg_isNull_17 = true;
/* 227 */ long sortAgg_value_17 = -1L;
/* 228 */
/* 229 */ if (!sortAgg_bufIsNull_2) {
/* 230 */ sortAgg_isNull_17 = false; // resultCode could change nullability.
/* 231 */
/* 232 */ sortAgg_value_17 = sortAgg_bufValue_2 + 1L;
/* 233 */
/* 234 */ }
/* 235 */ sortAgg_isNull_13 = sortAgg_isNull_17;
/* 236 */ sortAgg_value_13 = sortAgg_value_17;
/* 237 */ }
/* 238 */
/* 239 */ sortAgg_bufIsNull_1 = sortAgg_isNull_7;
/* 240 */ sortAgg_bufValue_1 = sortAgg_value_7;
/* 241 */
/* 242 */ sortAgg_bufIsNull_2 = sortAgg_isNull_13;
/* 243 */ sortAgg_bufValue_2 = sortAgg_value_13;
/* 244 */ }
/* 245 */
/* 246 */ }