cloud-fan commented on code in PR #40359:
URL: https://github.com/apache/spark/pull/40359#discussion_r1132460230
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sql/core/src/main/scala/org/apache/spark/sql/jdbc/OracleDialect.scala:
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@@ -181,19 +181,35 @@ private case object OracleDialect extends JdbcDialect {
if (limit > 0) s"WHERE rownum <= $limit" else ""
}
+ override def getOffsetClause(offset: Integer): String = {
+ // Oracle doesn't support OFFSET clause.
+ // We can use rownum > n to skip some rows in the result set.
+ // Note: rn is an alias of rownum.
+ if (offset > 0) s"WHERE rn > $offset" else ""
+ }
+
class OracleSQLQueryBuilder(dialect: JdbcDialect, options: JDBCOptions)
extends JdbcSQLQueryBuilder(dialect, options) {
- // TODO[SPARK-42289]: DS V2 pushdown could let JDBC dialect decide to push
down offset
override def build(): String = {
val selectStmt = s"SELECT $columnList FROM ${options.tableOrQuery}
$tableSampleClause" +
s" $whereClause $groupByClause $orderByClause"
- if (limit > 0) {
- val limitClause = dialect.getLimitClause(limit)
- options.prepareQuery + s"SELECT tab.* FROM ($selectStmt) tab
$limitClause"
+ val finalSelectStmt = if (limit > 0) {
+ if (offset > 0) {
+ s"SELECT $columnList FROM (SELECT tab.*, rownum rn FROM
($selectStmt) tab)" +
Review Comment:
or we can use the new syntax in oracle 12+, which should be the widely used
versions today.
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