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https://issues.apache.org/jira/browse/DRILL-4777?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15374543#comment-15374543
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Chunhui Shi commented on DRILL-4777:
------------------------------------
Example code pieces for function compare_to_nulls_high and hash32 embedded in
generated source HashTableGenNN.java:
3021: //---- start of eval portion of compare_to_nulls_high
function. ----//
3022: IntHolder out17 = new IntHolder();
3023: {
3024: final IntHolder out = new IntHolder();
3025: NullableBigIntHolder left = out12;
3026: NullableBigIntHolder right = out16;
3027:
3028:
GCompareBigIntVsBigInt$GCompareNullableBigIntVsNullableBigIntNullHigh_eval: {
3029: outside:
3030: {
3031: if (left.isSet == 0) {
3032: if (right.isSet == 0) {
3033: out.value = 0;
3034: break outside;
3035: } else
3036: {
3037: out.value = 1;
3038: break outside;
3039: }
3040: } else
3041: if (right.isSet == 0) {
3042: out.value = -1;
3043: break outside;
3044: }
3045: out.value = left.value < right.value ? -1 : (left.value ==
right.value ? 0 : 1);
3046: }
3047: }
3048:
3049: out17 = out;
3050: }
462: IntHolder out127 = new IntHolder();
463: {
464: final IntHolder out = new IntHolder();
465: NullableVarCharHolder in = out91;
466: IntHolder seed = out126;
467:
468: Hash32FunctionsWithSeed$NullableVarCharHash_eval: {
469: if (in.isSet == 0) {
470: out.value = seed.value;
471: } else
472: {
473: out.value =
org.apache.drill.exec.expr.fn.impl.XXHash.hash32(in.start, in.end, in.buffer,
seed.value);
474: }
475: }
476:
477: out127 = out;
478: }
479: //---- end of eval portion of hash32 function. ----//
> Fuse generated code to reduce code size and gain performance improvement
> ------------------------------------------------------------------------
>
> Key: DRILL-4777
> URL: https://issues.apache.org/jira/browse/DRILL-4777
> Project: Apache Drill
> Issue Type: Bug
> Reporter: Chunhui Shi
>
> Drill generates code for operators, compile the classes and load them on the
> fly of a query. However, in large query cases, the generated code will become
> hundreds KB or could be even bigger. We have seen multiple issues reported
> when generated code is too big either due to Java's size limit to one method
> or degrated performance of compiling or executing. Also when I looked at JIT
> optimization logs, there are many complaining about 'hot method too big'
> Some measures can be considered to reduce the code size, such as,
> 1) For now Drill embed function calls' code directly into generated code,
> this make one line function call to become 5-10 lines code in generated java
> classes. If we inject these functions as a private functions of the classes
> and directly call them in main function body, this could reduce code size
> while the cost of function call can be erased by JIT inline optimization.
> 2) Drill generate one variable for each column, if the column number became
> dozens to one hundred, the code will be redundant, we could consider using an
> array to store the value vectors and loop on top of it so the code size will
> be reduced even more.
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