[ https://issues.apache.org/jira/browse/DRILL-4834?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16322590#comment-16322590 ]
ASF GitHub Bot commented on DRILL-4834: --------------------------------------- Github user vvysotskyi commented on a diff in the pull request: https://github.com/apache/drill/pull/570#discussion_r160987506 --- Diff: exec/java-exec/src/main/codegen/templates/Decimal/CastDecimalVarchar.java --- @@ -150,6 +150,14 @@ public void setup() { public void eval() { +<#if type.from.contains("VarDecimal")> + java.math.BigDecimal bigDecimal = org.apache.drill.exec.util.DecimalUtility.getBigDecimalFromDrillBuf(in.buffer, in.start, in.end - in.start, in.scale); + String str = bigDecimal.toString(); + out.buffer = buffer; + out.start = 0; + out.end = Math.min((int)len.value, str.length()); + out.buffer.setBytes(0, str.getBytes()); --- End diff -- I guess we should do the same thing as for other decimals: ``` out.buffer.setBytes(0, String.valueOf(str.substring(0, out.end)).getBytes()); ``` > decimal implementation is vulnerable to overflow errors, and extremely complex > ------------------------------------------------------------------------------ > > Key: DRILL-4834 > URL: https://issues.apache.org/jira/browse/DRILL-4834 > Project: Apache Drill > Issue Type: Bug > Components: Execution - Data Types > Affects Versions: 1.6.0 > Environment: Drill 1.7 on any platform > Reporter: Dave Oshinsky > Assignee: Dave Oshinsky > Fix For: 1.13.0 > > > While working on a fix for DRILL-4704, logic was added to CastIntDecimal.java > template to handle the situation where a precision is not supplied (i.e., the > supplied precision is zero) for an integer value that is to be casted to a > decimal. The Drill decimal implementation uses a limited selection of fixed > decimal precision data types (the total number of decimal digits, i.e., > Decimal9, 18, 28, 38) to represent decimal values. If the destination > precision is too small to represent the input integer that is being casted, > there is no clean way to deal with the overflow error properly. > While using fixed decimal precisions as is being done currently can lead to > more efficient use of memory, it often will actually lead to less efficient > use of memory (when the fixed precision is specified significantly larger > than is actually needed to represent the numbers), and it results in a > tremendous mushrooming of the complexity of the code. For each fixed > precision (and there are only a limited set of selections, 9, 18, 28, 38, > which itself leads to memory inefficiency), there is a separate set of code > generated from templates. For each pairwise combination of decimal or > non-decimal numeric types, there are multiple places in the code where > conversions must be handled, or conditions must be included to handle the > difference in precision between the two types. A one-size-fits-all approach > (using a variable width vector to represent any decimal precision) would > usually be more memory-efficient (since precisions are often over-specified), > and would greatly simplify the code. > Also see the DRILL-4184 issue, which is related. -- This message was sent by Atlassian JIRA (v6.4.14#64029)