[GitHub] [spark] cloud-fan commented on a diff in pull request #40359: [SPARK-42740][SQL] Fix the bug that pushdown offset or paging is invalid for some built-in dialect
cloud-fan commented on code in PR #40359:
URL: https://github.com/apache/spark/pull/40359#discussion_r1132460230
##
sql/core/src/main/scala/org/apache/spark/sql/jdbc/OracleDialect.scala:
##
@@ -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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[GitHub] [spark] cloud-fan commented on a diff in pull request #40359: [SPARK-42740][SQL] Fix the bug that pushdown offset or paging is invalid for some built-in dialect
cloud-fan commented on code in PR #40359:
URL: https://github.com/apache/spark/pull/40359#discussion_r1132457170
##
sql/core/src/main/scala/org/apache/spark/sql/jdbc/OracleDialect.scala:
##
@@ -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:
https://stackoverflow.com/questions/31186166/oracle-sql-filtering-by-rownum-not-returning-results-when-it-should
Let's mention the reason as well: the `rownum` is calculated when the value
is returned.
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[GitHub] [spark] cloud-fan commented on a diff in pull request #40359: [SPARK-42740][SQL] Fix the bug that pushdown offset or paging is invalid for some built-in dialect
cloud-fan commented on code in PR #40359:
URL: https://github.com/apache/spark/pull/40359#discussion_r1132448651
##
sql/core/src/main/scala/org/apache/spark/sql/jdbc/MySQLDialect.scala:
##
@@ -291,4 +291,26 @@ private case object MySQLDialect extends JdbcDialect with
SQLConfHelper {
throw QueryExecutionErrors.unsupportedDropNamespaceRestrictError()
}
}
+
+ class MySQLSQLQueryBuilder(dialect: JdbcDialect, options: JDBCOptions)
+extends JdbcSQLQueryBuilder(dialect, options) {
+
+override def build(): String = {
+ if (limit < 1 && offset > 0) {
Review Comment:
is it possible to have limit = 0? seems safer to use `limit < 0` to indicate
no limit.
##
sql/core/src/main/scala/org/apache/spark/sql/jdbc/MySQLDialect.scala:
##
@@ -291,4 +291,26 @@ private case object MySQLDialect extends JdbcDialect with
SQLConfHelper {
throw QueryExecutionErrors.unsupportedDropNamespaceRestrictError()
}
}
+
+ class MySQLSQLQueryBuilder(dialect: JdbcDialect, options: JDBCOptions)
+extends JdbcSQLQueryBuilder(dialect, options) {
+
+override def build(): String = {
+ if (limit < 1 && offset > 0) {
Review Comment:
is it possible to have limit = 0? seems safer to use `limit < 0` to indicate
no limit, as the default value is -1
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[GitHub] [spark] cloud-fan commented on a diff in pull request #40359: [SPARK-42740][SQL] Fix the bug that pushdown offset or paging is invalid for some built-in dialect
cloud-fan commented on code in PR #40359:
URL: https://github.com/apache/spark/pull/40359#discussion_r1132007081
##
sql/core/src/main/scala/org/apache/spark/sql/jdbc/OracleDialect.scala:
##
@@ -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:
how about
```
SELECT * FROM ($selectStmt) tab WHERE rownum > ...
```
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[GitHub] [spark] cloud-fan commented on a diff in pull request #40359: [SPARK-42740][SQL] Fix the bug that pushdown offset or paging is invalid for some built-in dialect
cloud-fan commented on code in PR #40359:
URL: https://github.com/apache/spark/pull/40359#discussion_r1132005986
##
sql/core/src/main/scala/org/apache/spark/sql/jdbc/OracleDialect.scala:
##
@@ -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.
Review Comment:
nvm, I see the implementation.
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[GitHub] [spark] cloud-fan commented on a diff in pull request #40359: [SPARK-42740][SQL] Fix the bug that pushdown offset or paging is invalid for some built-in dialect
cloud-fan commented on code in PR #40359:
URL: https://github.com/apache/spark/pull/40359#discussion_r1132005699
##
sql/core/src/main/scala/org/apache/spark/sql/jdbc/OracleDialect.scala:
##
@@ -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.
Review Comment:
every table in oracle has the `rn` column?
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[GitHub] [spark] cloud-fan commented on a diff in pull request #40359: [SPARK-42740][SQL] Fix the bug that pushdown offset or paging is invalid for some built-in dialect
cloud-fan commented on code in PR #40359:
URL: https://github.com/apache/spark/pull/40359#discussion_r1132005206
##
sql/core/src/main/scala/org/apache/spark/sql/jdbc/MySQLDialect.scala:
##
@@ -291,4 +291,22 @@ private case object MySQLDialect extends JdbcDialect with
SQLConfHelper {
throw QueryExecutionErrors.unsupportedDropNamespaceRestrictError()
}
}
+
+ class MySQLSQLQueryBuilder(dialect: JdbcDialect, options: JDBCOptions)
+extends JdbcSQLQueryBuilder(dialect, options) {
+
+override def build(): String = {
+ if (limit < 1 && offset > 0) {
+val offsetClause = dialect.getOffsetClause(offset)
+options.prepareQuery +
+ s"SELECT $columnList FROM ${options.tableOrQuery}
$tableSampleClause" +
+ s" $whereClause $groupByClause $orderByClause LIMIT
18446744073709551610 $offsetClause"
Review Comment:
what does this `LIMIT 18446744073709551610` mean?
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[GitHub] [spark] cloud-fan commented on a diff in pull request #40359: [SPARK-42740][SQL] Fix the bug that pushdown offset or paging is invalid for some built-in dialect
cloud-fan commented on code in PR #40359:
URL: https://github.com/apache/spark/pull/40359#discussion_r1132004161
##
connector/docker-integration-tests/src/test/scala/org/apache/spark/sql/jdbc/v2/V2JDBCTest.scala:
##
@@ -410,6 +410,15 @@ private[v2] trait V2JDBCTest extends SharedSparkSession
with DockerIntegrationFu
assert(sorts.isEmpty)
}
+ private def checkOffsetPushed(df: DataFrame, offset: Option[Int]): Unit = {
Review Comment:
can we rename `limitPushed` to `checkLimitPushed` and follow the
implementation here?
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