BigQuery: Timestamp rounding issue #1644

Environment details

1. BigQuery
2. OS type and version: macOS
3. Java version: 8
4. bigquery version(s): at commit: 2b942da

Code example

I run the following query (note the last 3 digits are 574):

SELECT TIMESTAMP '2022-01-24T23:54:25.095574Z'

but I get back (note the last 3 digits are 573):

2022-01-24T23:54:25.095573Z

The following is a screen shot of the test and the result that I added to src/test/java/com/google/cloud/bigquery/it/ITBigQueryTest.java:

Seems the java client is affected by this issue, If I run the same query in BigQuery web console, the query returns correctly:

Steps to reproduce

apply this patch and run the "tmpTest" in src/test/java/com/google/cloud/bigquery/it/ITBigQueryTest.java.

Any additional information below

• Only certain timestamp values may cause the rounding error
• it seems that query priority has to be set to INTERATIVE to reproduce the rounding error
• Although BigQuery Timestamp is up to microsecond according to documentation, but the value in FieldValue (see screenshot above) actually returns 7 digits instead of 6 (again this only happens for certain timestamps).

the following patch fixes the problem by rounding the big decimal to neareast whole number before taking the longValue:

diff --git a/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/FieldValue.java b/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/FieldValue.java
index a2ce187..5bab4b3 100644
--- a/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/FieldValue.java
+++ b/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/FieldValue.java
@@ -25,6 +25,7 @@ import com.google.common.base.MoreObjects;
 import com.google.common.io.BaseEncoding;
 import java.io.Serializable;
 import java.math.BigDecimal;
+import java.math.RoundingMode;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -183,7 +184,7 @@ public class FieldValue implements Serializable {
     // timestamps are encoded in the format 1408452095.22 where the integer part is seconds since
     // epoch (e.g. 1408452095.22 == 2014-08-19 07:41:35.220 -05:00)
     BigDecimal secondsWithMicro = new BigDecimal(getStringValue());
-    BigDecimal scaled = secondsWithMicro.scaleByPowerOfTen(6);
+    BigDecimal scaled = secondsWithMicro.scaleByPowerOfTen(6).setScale(0, RoundingMode.HALF_UP);
     return scaled.longValue();
   }