StarSchema

Represents a StarSchema. The Star Schemas we support have the following constraints:

We only support one-one or many-one relations between entities.
A table can be related to the Fact Table via only 1 unique Path.
The column names across the Star Schema must be unique. So 2 tables in the Star Schema cannot have columns with the same name.

The first 2 points are not an issue only in the most involved star schema models; for e.g. we show how tpch can be modeled below. The 3rd restriction is an implementation issue: when performing QueryPlan rewrites we don't have access to the table an Attribute belongs to, for now we get around this issue by forcing column names to be unique across the Star Schema.

Tpch Model:

FactTable = LineItem
StarRelations: [
  LineItem - n:1 - Order => [[li_orderkey],[o_orderkey]]
  LineItem - n:1 - PartSupp => [[li_partkey, li_suppkey],[ps_partkey, ps_suppkey]]
  Order - n: 1 - Customer => [[o_custkey], [c_custkey]]
  PartSupp - n:1 - Part => [[ps_partkey], [p_partkey]]
  PartSupp - n:1 - Supplier => [[ps_suppkey], [s_suppkey]]
  Customer - n:1 - CustNation => [[c_nationkey], [cn_nationkey]]
  CustNation - n:1 - CustRegion => [[cn_regionkey], [cr_regionkey]]
  Supplier - n:1 - SupptNation => [[s_nationkey], [sn_nationkey]]
  SuppNation - n:1 - SuppRegion => [[sn_regionkey], [sr_regionkey]]
]

Because of our restrictions we have had to model the Nation table as separate CustNation and SuppNation tables. Similar separation has to be done for CustRegion and SuppRegion. Having to setup separate entities for Supplier and Customer Nation is not atypical when directly writing SQLs; these would be views on the same Nation Dimension table. Currently we are being more restrictive than this, we require the 2 views to be tables in the Metastore(this is because during Plan rewrite we loose the Table association in Attributereferences. But note, this doesn't require the data to be copied, both tables can point to the same underlying data in the storage layer.

We have to rename the column names in the 2 Nation(and region) tables. This is so that we can infer the Attribute to Tables(in the Star Schema) associations in a Query Plan.

info: the StarSchemaInfo used to build this StarSchema Graph.
factTable: the node that represents the Fact Table
tableMap: maps a tableName to the StarTable node in the StarSchema Graph.
attrMap: provides a mapping from a columnName to its table.

Linear Supertypes

Serializable, Serializable, Product, Equals, AnyRef, Any

Instance Constructors

new StarSchema(info: StarSchemaInfo, factTable: StarTable, tableMap: Map[String, StarTable], attrMap: Map[String, StarTable])

info
the StarSchemaInfo used to build this StarSchema Graph.
factTable
the node that represents the Fact Table
tableMap
maps a tableName to the StarTable node in the StarSchema Graph.
attrMap
provides a mapping from a columnName to its table.

Value Members

final def !=(arg0: AnyRef): Boolean

Definition Classes
AnyRef
final def !=(arg0: Any): Boolean

Definition Classes
Any
final def ##(): Int

Definition Classes
AnyRef → Any
final def ==(arg0: AnyRef): Boolean

Definition Classes
AnyRef
final def ==(arg0: Any): Boolean

Definition Classes
Any
final def asInstanceOf[T0]: T0

Definition Classes
Any
val attrMap: Map[String, StarTable]

provides a mapping from a columnName to its table.
def clone(): AnyRef

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws( ... )
final def eq(arg0: AnyRef): Boolean

Definition Classes
AnyRef
val factTable: StarTable

the node that represents the Fact Table
def finalize(): Unit

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws( classOf[java.lang.Throwable] )
final def getClass(): Class[_]

Definition Classes
AnyRef → Any
def getUniqueTable(joinKeys: Seq[Expression]): Option[String]

The seq of expressions representing one side of a join must all be AttributeReferences and must be from the same table.
The seq of expressions representing one side of a join must all be AttributeReferences and must be from the same table. If this condition is met, the table's name is returned.
joinKeys
returns
val info: StarSchemaInfo

the StarSchemaInfo used to build this StarSchema Graph.
def isAttributeReference(e: Expression): Boolean
final def isInstanceOf[T0]: Boolean

Definition Classes
Any
def isStarJoin(leftJoinKeys: Seq[Expression], rightJoinKeys: Seq[Expression]): Option[(String, String)]

Does the join predicate represented by the left and right join keys match a join in the StarSchema.
Does the join predicate represented by the left and right join keys match a join in the StarSchema. So a join like
```
lineitem li join part p on li.l_partkey = p.p_partkey
```
is represented as
```
Seq(AttributeReference("l_partkey")), Seq(AttributeReference("p_partkey"))
```
The following constraints must be met for the joining condition to be a join from this StarSchema:
- Every joining expressions can only be an AttributeReference
- each set of joining conditions(leftJoinKeys, rightJoinKeys) must be on 1 table.
- the 2 tables must be related in the StarSchema.
- the matching Attributes in the input(leftJoinKeys, rightJoinKeys) must exactly nmatch the joining key defined in the StarSchema for the 2 tables involved.
lineitem li join part p on li.l_partkey = p.p_partkey }}} represented as
```
Seq(AttributeReference("l_partkey")), Seq(AttributeReference("p_partkey"))
```
The following constraints must be met for the joining condition to be a join from this StarSchema:
- Every joining expressions can only be an AttributeReference
- each set of joining conditions(leftJoinKeys, rightJoinKeys) must be on 1 table.
- the 2 tables must be related in the StarSchema.
- the matching Attributes in the input(leftJoinKeys, rightJoinKeys) must exactly nmatch the joining key defined in the StarSchema for the 2 tables involved.
leftJoinKeys
rightJoinKeys
returns
final def ne(arg0: AnyRef): Boolean

Definition Classes
AnyRef
final def notify(): Unit

Definition Classes
AnyRef
final def notifyAll(): Unit

Definition Classes
AnyRef
def prettyString: String
final def synchronized[T0](arg0: ⇒ T0): T0

Definition Classes
AnyRef
val tableMap: Map[String, StarTable]

maps a tableName to the StarTable node in the StarSchema Graph.
final def wait(): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
final def wait(arg0: Long, arg1: Int): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
final def wait(arg0: Long): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )

case class StarSchema(info: StarSchemaInfo, factTable: StarTable, tableMap: Map[String, StarTable], attrMap: Map[String, StarTable]) extends Product with Serializable

Instance Constructors

new StarSchema(info: StarSchemaInfo, factTable: StarTable, tableMap: Map[String, StarTable], attrMap: Map[String, StarTable])

Value Members

final def !=(arg0: AnyRef): Boolean

final def !=(arg0: Any): Boolean

final def ##(): Int

final def ==(arg0: AnyRef): Boolean

final def ==(arg0: Any): Boolean

final def asInstanceOf[T0]: T0

val attrMap: Map[String, StarTable]

def clone(): AnyRef

final def eq(arg0: AnyRef): Boolean

val factTable: StarTable

def finalize(): Unit

final def getClass(): Class[_]

def getUniqueTable(joinKeys: Seq[Expression]): Option[String]

val info: StarSchemaInfo

def isAttributeReference(e: Expression): Boolean

final def isInstanceOf[T0]: Boolean

def isStarJoin(leftJoinKeys: Seq[Expression], rightJoinKeys: Seq[Expression]): Option[(String, String)]

final def ne(arg0: AnyRef): Boolean

final def notify(): Unit

final def notifyAll(): Unit

def prettyString: String

final def synchronized[T0](arg0: ⇒ T0): T0

val tableMap: Map[String, StarTable]

final def wait(): Unit

final def wait(arg0: Long, arg1: Int): Unit

final def wait(arg0: Long): Unit

Inherited from Serializable

Inherited from Serializable

Inherited from Product

Inherited from Equals

Inherited from AnyRef

Inherited from Any

Ungrouped