Are you looking for this: https://spark.apache.org/docs/2.4.0/api/sql/#when ?
The code generated will look like this in a `do { ... } while (false)` loop:
do {
${cond.code}
if (!${cond.isNull} && ${cond.value}) {
${res.code}
$resultState = (byte)(${res.isNull} ? $HAS_NULL : $HAS_NONNULL);
${ev.value} = ${res.value};
continue;
}
<and the following CASE conditions ...>
} while (false)
Refer to:
https://github.com/apache/spark/blob/master/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionalExpressions.scala#L208
Here is a full generated code sample for `spark.sql("select CASE WHEN age IS
NULL THEN 'unknown' WHEN age < 30 THEN 'young' WHEN age < 40 THEN 'middle' ELSE
'senior' END, name from people").show()` :
/* 034 */ byte project_caseWhenResultState_0 = -1;
/* 035 */ do {
/* 036 */ if (!false && scan_isNull_0) {
/* 037 */ project_caseWhenResultState_0 = (byte)(false ? 1 : 0);
/* 038 */ project_mutableStateArray_0[0] = ((UTF8String)
references[1] /* literal */);
/* 039 */ continue;
/* 040 */ }
/* 041 */
/* 042 */ boolean project_isNull_4 = true;
/* 043 */ boolean project_value_4 = false;
/* 044 */
/* 045 */ if (!scan_isNull_0) {
/* 046 */ project_isNull_4 = false; // resultCode could change
nullability.
/* 047 */ project_value_4 = scan_value_0 < 30L;
/* 048 */
/* 049 */ }
/* 050 */ if (!project_isNull_4 && project_value_4) {
/* 051 */ project_caseWhenResultState_0 = (byte)(false ? 1 : 0);
/* 052 */ project_mutableStateArray_0[0] = ((UTF8String)
references[2] /* literal */);
/* 053 */ continue;
/* 054 */ }
/* 055 */
/* 056 */ boolean project_isNull_8 = true;
/* 057 */ boolean project_value_8 = false;
/* 058 */
/* 059 */ if (!scan_isNull_0) {
/* 060 */ project_isNull_8 = false; // resultCode could change
nullability.
/* 061 */ project_value_8 = scan_value_0 < 40L;
/* 062 */
/* 063 */ }
/* 064 */ if (!project_isNull_8 && project_value_8) {
/* 065 */ project_caseWhenResultState_0 = (byte)(false ? 1 : 0);
/* 066 */ project_mutableStateArray_0[0] = ((UTF8String)
references[3] /* literal */);
/* 067 */ continue;
/* 068 */ }
/* 069 */
/* 070 */ project_caseWhenResultState_0 = (byte)(false ? 1 : 0);
/* 071 */ project_mutableStateArray_0[0] = ((UTF8String) references[4]
/* literal */);
/* 072 */
/* 073 */ } while (false);
Cheers,
-z
________________________________________
From: Yeikel <em...@yeikel.com>
Sent: Wednesday, April 15, 2020 2:22
To: user@spark.apache.org
Subject: Re: How does spark sql evaluate case statements?
I do not know the answer to this question so I am also looking for it, but
@kant maybe the generated code can help with this.
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Sent from: http://apache-spark-user-list.1001560.n3.nabble.com/
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