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https://issues.apache.org/jira/browse/OLINGO-1087?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15891918#comment-15891918
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Ralf Handl commented on OLINGO-1087:
------------------------------------
OData V2's data type Edm.Decimal follows the rules for the SQL type
DECIMAL(p,s) or NUMBER(p,s), see e.g.
https://msdn.microsoft.com/en-us/library/ms190476.aspx. It is a decimally
stored fixed-point number, see
https://en.wikipedia.org/wiki/Fixed-point_arithmetic.
Precision in this context is the length of the decimal mantissa, and Scale is
the negative exponent of the base-10 scaling factor. This means that you have
to take both Precision and Scale into account in this discussion.
For the rather lengthy number above you'd need Precision=35 and Scale=35 to
store it losslessly in a DECIMAL column of a SQL database, limiting you to
storing numbers that are greater than -1 and less than 1 with 35 decimal digits
to the right of the decimal point.
Example 17 in
http://docs.oasis-open.org/odata/odata-csdl-xml/v4.01/csprd01/odata-csdl-xml-v4.01-csprd01.html#_Toc472333020
explains this for the more readable case of Precision=2 and Scale=2.
> Precision in EdmDecimal not calculated correctly
> ------------------------------------------------
>
> Key: OLINGO-1087
> URL: https://issues.apache.org/jira/browse/OLINGO-1087
> Project: Olingo
> Issue Type: Bug
> Components: odata2-core
> Affects Versions: V2 2.0.8
> Reporter: Svante von Erichsen
> Attachments: 0001-OLINGO-1087-Fix-calculation-of-precision.patch
>
>
> The "precision" found in a read number is currently at least the number of
> decimals (omitting trailing zeroes). That seems to be wrong, or at least not
> consistent with at least some server side view of the matter, for numbers
> smaller than 0.1 (the number shown has 35 decimals, but precision 34):
> org.apache.olingo.odata2.api.edm.EdmSimpleTypeException: The metadata
> constraints '[Precision=34]' do not match the literal
> '0.08102359900000000170194880411145277'.
> at
> org.apache.olingo.odata2.core.edm.EdmDecimal.internalValueOfString(EdmDecimal.java:107)
> at
> org.apache.olingo.odata2.core.edm.AbstractSimpleType.valueOfString(AbstractSimpleType.java:91)
> at
> org.apache.olingo.odata2.core.ep.consumer.JsonPropertyConsumer.readSimpleProperty(JsonPropertyConsumer.java:236)
> at
> org.apache.olingo.odata2.core.ep.consumer.JsonPropertyConsumer.readPropertyValue(JsonPropertyConsumer.java:169)
> ... 69 common frames omitted
> Wrapped by: org.apache.olingo.odata2.api.ep.EntityProviderException: An
> exception of type 'EdmSimpleTypeException' occurred.
> at
> org.apache.olingo.odata2.core.ep.consumer.JsonPropertyConsumer.readPropertyValue(JsonPropertyConsumer.java:171)
> at
> org.apache.olingo.odata2.core.ep.consumer.JsonEntryConsumer.handleName(JsonEntryConsumer.java:172)
> at
> org.apache.olingo.odata2.core.ep.consumer.JsonEntryConsumer.readEntryContent(JsonEntryConsumer.java:130)
> at
> org.apache.olingo.odata2.core.ep.consumer.JsonEntryConsumer.readFeedEntry(JsonEntryConsumer.java:117)
> at
> org.apache.olingo.odata2.core.ep.consumer.JsonFeedConsumer.readArrayContent(JsonFeedConsumer.java:153)
> at
> org.apache.olingo.odata2.core.ep.consumer.JsonFeedConsumer.handleName(JsonFeedConsumer.java:122)
> at
> org.apache.olingo.odata2.core.ep.consumer.JsonFeedConsumer.readFeedContent(JsonFeedConsumer.java:111)
> at
> org.apache.olingo.odata2.core.ep.consumer.JsonFeedConsumer.readFeed(JsonFeedConsumer.java:96)
> at
> org.apache.olingo.odata2.core.ep.consumer.JsonFeedConsumer.readFeedStandalone(JsonFeedConsumer.java:63)
> at
> org.apache.olingo.odata2.core.ep.consumer.JsonEntityConsumer.readDeltaFeed(JsonEntityConsumer.java:95)
> at
> org.apache.olingo.odata2.core.ep.consumer.JsonEntityConsumer.readFeed(JsonEntityConsumer.java:81)
> at
> org.apache.olingo.odata2.core.ep.JsonEntityProvider.readFeed(JsonEntityProvider.java:309)
> at
> org.apache.olingo.odata2.core.ep.ProviderFacadeImpl.readFeed(ProviderFacadeImpl.java:165)
> at
> org.apache.olingo.odata2.api.ep.EntityProvider.readFeed(EntityProvider.java:676)
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