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https://issues.apache.org/jira/browse/PHOENIX-2018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14570149#comment-14570149
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James Taylor commented on PHOENIX-2018:
---------------------------------------
Thanks for the patch, [~shuxi0ng]. It looks very good. Here's some minor
feedback:
- In your evaluate method, check for the child evaluating to null (which you
can check with ptr.getLength() == 0), and in that case, just return true.
- Remove that if (ptr.getLength() < returnType.getByteSize()) statement. You
definitely always need to allocate a new buffer for the return value, otherwise
you're potentially overriding some random memory location (based on what the
child returned).
- Don't bother coercing the value after the Math.sqrt call. Instead, just don't
specialize the getSortOrder() method (which will end up defaulting to
SortOrder.ASC).
{code}
+ @Override
+ public boolean evaluate(Tuple tuple, ImmutableBytesWritable ptr) {
+ Expression childExpr = children.get(0);
+ PDataType returnType = getDataType();
+ if (childExpr.evaluate(tuple, ptr)) {
+ double result;
+ if (childExpr.getDataType() == PDecimal.INSTANCE) {
+ result =
+ ((BigDecimal) childExpr.getDataType().toObject(ptr,
+ childExpr.getSortOrder())).doubleValue();
+ } else {
+ result =
+ childExpr.getDataType().getCodec()
+ .decodeDouble(ptr, childExpr.getSortOrder());
+ }
+ if (ptr.getLength() < returnType.getByteSize()) {
+ ptr.set(new byte[returnType.getByteSize()]);
+ }
+ returnType.getCodec().encodeDouble(Math.sqrt(result), ptr);
+ returnType.coerceBytes(ptr, returnType, SortOrder.ASC,
childExpr.getSortOrder());
+ return true;
+ }
+ return false;
+ }
{code}
+
+ @Override
+ public PDataType getDataType() {
+ return PDouble.INSTANCE;
+ }
+
+ @Override
+ public String getName() {
+ return NAME;
+ }
+
+ @Override
+ public OrderPreserving preservesOrder() {
+ return OrderPreserving.YES;
+ }
+
+ @Override
+ public SortOrder getSortOrder() {
+ return children.get(0).getSortOrder();
+ }
{code}
> Implement math build-in function SQRT
> -------------------------------------
>
> Key: PHOENIX-2018
> URL: https://issues.apache.org/jira/browse/PHOENIX-2018
> Project: Phoenix
> Issue Type: Sub-task
> Reporter: Shuxiong Ye
> Assignee: Shuxiong Ye
> Fix For: 5.0.0, 4.5.0, 4.4.1
>
> Attachments:
> 0001-PHOENIX-2018-Implement-math-build-in-function-SQRT_v3.patch
>
>
> # SQRT means square root.
> # Return type will be PDouble
> # OrderPreserving
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