Revert OFFSET (due to clash with existing SQL Functions)

Author: CHAZOTA

sqlest/src/main/scala/sqlest/sql/DB2StatementBuilder.scala

@@ -57,28 +57,19 @@ trait DB2StatementBuilder extends base.StatementBuilder {
     }
 
   override def selectSql(select: Select[_, _ <: Relation]): String = {
-    Seq(
-      selectWhatSql(select.columns),
-      selectFromSql(select.from)
-    ) ++ Seq(
-        selectWhereSql(select.where),
-        selectStartWithSql(select.startWith),
-        selectConnectBySql(select.connectBy),
-        selectGroupBySql(select.groupBy),
-        selectHavingSql(select.having),
-        selectOrderBySql(select.orderBy),
-        selectOffsetSql(select.offset),
-        selectLimitSql(select.limit),
-        selectOptimizeSql(select.optimize),
-        selectUnionSql(select.union)
-      ).flatten mkString (" ")
+    val offset = select.offset getOrElse 0L
+    if (offset > 0L) {
+      rowNumberSelectSql(select, offset, select.limit)
+    } else {
+      super.selectSql(select)
+    }
   }
 
   override def selectLimitSql(limit: Option[Long]): Option[String] =
     limit map (limit => s"fetch first $limit rows only")
 
   override def selectOffsetSql(offset: Option[Long]): Option[String] =
-    offset map (offset => s"offset ${literalSql(offset)} rows")
+    None
 
   override def selectOptimizeSql(optimize: Option[Long]): Option[String] =
     optimize map (optimize => s"optimize for $optimize rows")
@@ -91,6 +82,25 @@ trait DB2StatementBuilder extends base.StatementBuilder {
     case _ => super.joinSql(relation)
   }
 
+  def rowNumberSelectSql(select: Select[_, _ <: Relation], offset: Long, limit: Option[Long]): String = {
+    val subquery = Seq(
+      s"${selectWhatSql(select.columns)}, row_number() over (${selectOrderBySql(select.orderBy) getOrElse ""}) as rownum",
+      selectFromSql(select.from)
+    ) ++ Seq(
+        selectWhereSql(select.where),
+        selectGroupBySql(select.groupBy)
+      ).flatten mkString " "
+
+    val what =
+      select.columns map (col => identifierSql(col.columnAlias)) mkString ", "
+
+    val bounds = limit
+      .map(limit => s"rownum between ? and ?")
+      .getOrElse(s"rownum >= ?")
+
+    s"with subquery as ($subquery) select $what from subquery where $bounds"
+  }
+
   override def columnSql(column: Column[_]): String =
     column match {
       case literalColumn: LiteralColumn[_] if literalColumn.columnType == BooleanColumnType =>
@@ -100,12 +110,38 @@ trait DB2StatementBuilder extends base.StatementBuilder {
       case _ => super.columnSql(column)
     }
 
+  override def selectArgs(select: Select[_, _ <: Relation]): List[LiteralColumn[_]] = {
+    val offset = select.offset getOrElse 0L
+    if (offset > 0L) {
+      rowNumberSelectArgs(select, offset, select.limit)
+    } else {
+      super.selectArgs(select)
+    }
+  }
+
   override def selectLimitArgs(limit: Option[Long]): List[LiteralColumn[_]] =
     Nil
 
+  override def selectOffsetArgs(limit: Option[Long]): List[LiteralColumn[_]] =
+    Nil
+
   override def selectOptimizeArgs(optimize: Option[Long]): List[LiteralColumn[_]] =
     Nil
 
+  def rowNumberSelectArgs(select: Select[_, _ <: Relation], offset: Long, limit: Option[Long]): List[LiteralColumn[_]] = {
+    val subqueryArgs =
+      selectWhatArgs(select.columns) ++
+        selectOrderByArgs(select.orderBy) ++
+        selectFromArgs(select.from) ++
+        selectWhereArgs(select.where)
+
+    val boundsArgs = limit
+      .map(limit => List(LiteralColumn[Long](offset + 1), LiteralColumn[Long](offset + limit)))
+      .getOrElse(List(LiteralColumn[Long](offset + 1)))
+
+    subqueryArgs ++ boundsArgs
+  }
+
   override def columnArgs(column: Column[_]): List[LiteralColumn[_]] = column match {
     case column: LiteralColumn[_] if column.columnType == BooleanColumnType => List(LiteralColumn(0), LiteralColumn(0))
     case _ => super.columnArgs(column)

sqlest/src/test/scala/sqlest/sql/DB2StatementBuilderSpec.scala

@@ -51,12 +51,15 @@ class DB2StatementBuilderSpec extends BaseStatementBuilderSpec {
         .offset(20)
     } should equal(
       s"""
-       |select mytable.col1 as mytable_col1, mytable.col2 as mytable_col2
-       |from mytable
-       |where (mytable.col1 = ?)
-       |offset ? rows
+       |with subquery as
+       |(select mytable.col1 as mytable_col1, mytable.col2 as mytable_col2, row_number() over () as rownum
+         |from mytable
+         |where (mytable.col1 = ?))
+       |select mytable_col1, mytable_col2
+       |from subquery
+       |where rownum >= ?
        """.formatSql,
-      List(List(123, 20))
+      List(List(123, 2 * 10 + 1))
     )
   }
 
@@ -68,13 +71,15 @@ class DB2StatementBuilderSpec extends BaseStatementBuilderSpec {
         .page(2, 10)
     } should equal(
       s"""
-       |select mytable.col1 as mytable_col1, mytable.col2 as mytable_col2
-       |from mytable
-       |where (mytable.col1 = ?)
-       |offset ? rows
-       |fetch first 10 rows only
+       |with subquery as
+       |(select mytable.col1 as mytable_col1, mytable.col2 as mytable_col2, row_number() over () as rownum
+         |from mytable
+         |where (mytable.col1 = ?))
+       |select mytable_col1, mytable_col2
+       |from subquery
+       |where rownum between ? and ?
        """.formatSql,
-      List(List(123, 2 * 10))
+      List(List(123, 2 * 10 + 1, 2 * 10 + 10))
     )
   }
 
@@ -87,14 +92,15 @@ class DB2StatementBuilderSpec extends BaseStatementBuilderSpec {
         .page(2, 10)
     } should equal(
       s"""
-       |select mytable.col1 as mytable_col1, mytable.col2 as mytable_col2
-       |from mytable
-       |where (mytable.col1 = ?)
-       |order by mytable.col1
-       |offset ? rows
-       |fetch first 10 rows only
+       |with subquery as
+       |(select mytable.col1 as mytable_col1, mytable.col2 as mytable_col2, row_number() over (order by mytable.col1) as rownum
+         |from mytable
+         |where (mytable.col1 = ?))
+       |select mytable_col1, mytable_col2
+       |from subquery
+       |where rownum between ? and ?
        """.formatSql,
-      List(List(123, 2 * 10))
+      List(List(123, 2 * 10 + 1, 2 * 10 + 10))
     )
   }
 
@@ -166,15 +172,15 @@ class DB2StatementBuilderSpec extends BaseStatementBuilderSpec {
         .optimize(10)
     } should equal(
       s"""
-       |select mytable.col1 as mytable_col1, mytable.col2 as mytable_col2
-       |from mytable
-       |where (mytable.col1 = ?)
-       |order by mytable.col1
-       |offset ? rows
-       |fetch first 10 rows only
-       |optimize for 10 rows
+       |with subquery as
+       |(select mytable.col1 as mytable_col1, mytable.col2 as mytable_col2, row_number() over (order by mytable.col1) as rownum
+         |from mytable
+         |where (mytable.col1 = ?))
+       |select mytable_col1, mytable_col2
+       |from subquery
+       |where rownum between ? and ?
        """.formatSql,
-      List(List(123, 10))
+      List(List(123, 11, 20))
     )
   }
 
@@ -187,14 +193,15 @@ class DB2StatementBuilderSpec extends BaseStatementBuilderSpec {
         .page(15, 16)
     } should equal(
       s"""
-       |select 1 as a, sum(cast(? as integer)) as b, (3 + ?) as c
-       |from one inner join two on ((? = ?) and (? <> ?))
-       |where ((? = ?) and (? <> ?))
-       |order by ?, ? desc
-       |offset ? rows
-       |fetch first 16 rows only     
+       |with subquery as
+       |(select 1 as a, sum(cast(? as integer)) as b, (3 + ?) as c, row_number() over (order by ?, ? desc) as rownum
+         |from one inner join two on ((? = ?) and (? <> ?))
+         |where ((? = ?) and (? <> ?)))
+       |select a, b, c
+       |from subquery
+       |where rownum between ? and ?
        """.formatSql,
-      List(List(2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 * 16))
+      List(List(2, 4, 13, 14, 5, 6, 7, 8, 9, 10, 11, 12, 15 * 16 + 1, 15 * 16 + 16))
     )
   }