[GitHub] [spark] cloud-fan commented on a diff in pull request #41843: [SPARK-44280][SQL] Add convertJavaTimestampToTimestamp in JDBCDialect API

["cloud-fan (via GitHub)" <gi...@apache.org>]

cloud-fan commented on code in PR #41843:
URL: https://github.com/apache/spark/pull/41843#discussion_r1254909622


##########
sql/core/src/main/scala/org/apache/spark/sql/jdbc/PostgresDialect.scala:
##########
@@ -281,4 +282,28 @@ private object PostgresDialect extends JdbcDialect with SQLConfHelper {
     }
     s"ALTER TABLE ${getFullyQualifiedQuotedTableName(oldTable)} RENAME TO ${newTable.name()}"
   }
+
+  /**
+   * PostgreSQL has four special "infinity values" that we need clamp to avoid overflow.
+   * If it is not one of the infinity values, fall back to default behavior. */
+  override def convertJavaTimestampToTimestamp(t: Timestamp): Long = {
+    // Variable names come from PostgreSQL "constant field docs":
+    // https://jdbc.postgresql.org/documentation/publicapi/index.html?constant-values.html
+    val POSTGRESQL_DATE_NEGATIVE_INFINITY = -9223372036832400000L
+    val POSTGRESQL_DATE_NEGATIVE_SMALLER_INFINITY = -185543533774800000L
+    val POSTGRESQL_DATE_POSITIVE_INFINITY = 9223372036825200000L
+    val POSTGRESQL_DATE_DATE_POSITIVE_SMALLER_INFINITY = 185543533774800000L
+
+    val time = t.getTime
+
+    if (time == POSTGRESQL_DATE_POSITIVE_INFINITY ||
+      time == POSTGRESQL_DATE_DATE_POSITIVE_SMALLER_INFINITY) {
+      Long.MaxValue

Review Comment:
   If we query a infinite timestamp column in pgsql, what does pgsql display?



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