[SPARK-21870][SQL] Split aggregation code into small functions
## What changes were proposed in this pull request?
This pr proposed to split aggregation code into small functions in `HashAggregateExec`. In #18810, we got performance regression if JVMs didn't compile too long functions. I checked and I found the codegen of `HashAggregateExec` frequently goes over the limit when a query has too many aggregate functions (e.g., q66 in TPCDS).
The current master places all the generated aggregation code in a single function. In this pr, I modified the code to assign an individual function for each aggregate function (e.g., `SUM`
and `AVG`). For example, in a query
`SELECT SUM(a), AVG(a) FROM VALUES(1) t(a)`, the proposed code defines two functions
for `SUM(a)` and `AVG(a)` as follows;
- generated code with this pr (https://gist.github.com/maropu/812990012bc967a78364be0fa793f559):
```
/* 173 */ private void agg_doConsume_0(InternalRow inputadapter_row_0, long agg_expr_0_0, boolean agg_exprIsNull_0_0, double agg_expr_1_0, boolean agg_exprIsNull_1_0, long agg_expr_2_0, boolean agg_exprIsNull_2_0) throws java.io.IOException {
/* 174 */ // do aggregate
/* 175 */ // common sub-expressions
/* 176 */
/* 177 */ // evaluate aggregate functions and update aggregation buffers
/* 178 */ agg_doAggregate_sum_0(agg_exprIsNull_0_0, agg_expr_0_0);
/* 179 */ agg_doAggregate_avg_0(agg_expr_1_0, agg_exprIsNull_1_0, agg_exprIsNull_2_0, agg_expr_2_0);
/* 180 */
/* 181 */ }
...
/* 071 */ private void agg_doAggregate_avg_0(double agg_expr_1_0, boolean agg_exprIsNull_1_0, boolean agg_exprIsNull_2_0, long agg_expr_2_0) throws java.io.IOException {
/* 072 */ // do aggregate for avg
/* 073 */ // evaluate aggregate function
/* 074 */ boolean agg_isNull_19 = true;
/* 075 */ double agg_value_19 = -1.0;
...
/* 114 */ private void agg_doAggregate_sum_0(boolean agg_exprIsNull_0_0, long agg_expr_0_0) throws java.io.IOException {
/* 115 */ // do aggregate for sum
/* 116 */ // evaluate aggregate function
/* 117 */ agg_agg_isNull_11_0 = true;
/* 118 */ long agg_value_11 = -1L;
```
- generated code in the current master (https://gist.github.com/maropu/e9d772af2c98d8991a6a5f0af7841760)
```
/* 059 */ private void agg_doConsume_0(InternalRow localtablescan_row_0, int agg_expr_0_0) throws java.io.IOException {
/* 060 */ // do aggregate
/* 061 */ // common sub-expressions
/* 062 */ boolean agg_isNull_4 = false;
/* 063 */ long agg_value_4 = -1L;
/* 064 */ if (!false) {
/* 065 */ agg_value_4 = (long) agg_expr_0_0;
/* 066 */ }
/* 067 */ // evaluate aggregate function
/* 068 */ agg_agg_isNull_7_0 = true;
/* 069 */ long agg_value_7 = -1L;
/* 070 */ do {
/* 071 */ if (!agg_bufIsNull_0) {
/* 072 */ agg_agg_isNull_7_0 = false;
/* 073 */ agg_value_7 = agg_bufValue_0;
/* 074 */ continue;
/* 075 */ }
/* 076 */
/* 077 */ boolean agg_isNull_9 = false;
/* 078 */ long agg_value_9 = -1L;
/* 079 */ if (!false) {
/* 080 */ agg_value_9 = (long) 0;
/* 081 */ }
/* 082 */ if (!agg_isNull_9) {
/* 083 */ agg_agg_isNull_7_0 = false;
/* 084 */ agg_value_7 = agg_value_9;
/* 085 */ continue;
/* 086 */ }
/* 087 */
/* 088 */ } while (false);
/* 089 */
/* 090 */ long agg_value_6 = -1L;
/* 091 */
/* 092 */ agg_value_6 = agg_value_7 + agg_value_4;
/* 093 */ boolean agg_isNull_11 = true;
/* 094 */ double agg_value_11 = -1.0;
/* 095 */
/* 096 */ if (!agg_bufIsNull_1) {
/* 097 */ agg_agg_isNull_13_0 = true;
/* 098 */ double agg_value_13 = -1.0;
/* 099 */ do {
/* 100 */ boolean agg_isNull_14 = agg_isNull_4;
/* 101 */ double agg_value_14 = -1.0;
/* 102 */ if (!agg_isNull_4) {
/* 103 */ agg_value_14 = (double) agg_value_4;
/* 104 */ }
/* 105 */ if (!agg_isNull_14) {
/* 106 */ agg_agg_isNull_13_0 = false;
/* 107 */ agg_value_13 = agg_value_14;
/* 108 */ continue;
/* 109 */ }
/* 110 */
/* 111 */ boolean agg_isNull_15 = false;
/* 112 */ double agg_value_15 = -1.0;
/* 113 */ if (!false) {
/* 114 */ agg_value_15 = (double) 0;
/* 115 */ }
/* 116 */ if (!agg_isNull_15) {
/* 117 */ agg_agg_isNull_13_0 = false;
/* 118 */ agg_value_13 = agg_value_15;
/* 119 */ continue;
/* 120 */ }
/* 121 */
/* 122 */ } while (false);
/* 123 */
/* 124 */ agg_isNull_11 = false; // resultCode could change nullability.
/* 125 */
/* 126 */ agg_value_11 = agg_bufValue_1 + agg_value_13;
/* 127 */
/* 128 */ }
/* 129 */ boolean agg_isNull_17 = false;
/* 130 */ long agg_value_17 = -1L;
/* 131 */ if (!false && agg_isNull_4) {
/* 132 */ agg_isNull_17 = agg_bufIsNull_2;
/* 133 */ agg_value_17 = agg_bufValue_2;
/* 134 */ } else {
/* 135 */ boolean agg_isNull_20 = true;
/* 136 */ long agg_value_20 = -1L;
/* 137 */
/* 138 */ if (!agg_bufIsNull_2) {
/* 139 */ agg_isNull_20 = false; // resultCode could change nullability.
/* 140 */
/* 141 */ agg_value_20 = agg_bufValue_2 + 1L;
/* 142 */
/* 143 */ }
/* 144 */ agg_isNull_17 = agg_isNull_20;
/* 145 */ agg_value_17 = agg_value_20;
/* 146 */ }
/* 147 */ // update aggregation buffer
/* 148 */ agg_bufIsNull_0 = false;
/* 149 */ agg_bufValue_0 = agg_value_6;
/* 150 */
/* 151 */ agg_bufIsNull_1 = agg_isNull_11;
/* 152 */ agg_bufValue_1 = agg_value_11;
/* 153 */
/* 154 */ agg_bufIsNull_2 = agg_isNull_17;
/* 155 */ agg_bufValue_2 = agg_value_17;
/* 156 */
/* 157 */ }
```
You can check the previous discussion in https://github.com/apache/spark/pull/19082
## How was this patch tested?
Existing tests
Closes #20965 from maropu/SPARK-21870-2.
Authored-by: Takeshi Yamamuro <yamamuro@apache.org>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
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