Quadcap Embeddable Database

Tuples and Columns

public interface Tuple {
    public int numColumns();
    public Column getColumn(int i);
}

public interface Column {
    public String getName();
    public Type getType();
    public boolean isFixed();
    public int getOffset();
    public int getLength();
    public Enumeration getConstraints();
}

public interface Table extends Tuple {
    public int numRows();
    public Row getRow(int i);
    public Enumeration getConstraints();
    public Constraint getPrimaryKeyConstraint();
}

public interface Row extends Tuple {
    public Row(Tuple def, byte[] bytes);
}

public interface Index {
    public Tuple getBaseType();

    /**
     * Return an enumeration of the keys of this index, in order, starting
     * with the first index value not less than first
     */
    public Enumeration enumerate(TupleValue first);

    /**
     * Return an enumeration of the keys of this index, in reverse order,
     * starting with the first index value not greater than last
     */
    public Enumeration reverseEnumerate(TupleValue last);
}

public interface Type {
    public String getTypeName();
    public int compare(Type other);

    public void setBytes(byte[] buf, int offset, int cnt);
    public byte[] getBytes();

    public Object getObject();
    public void setObject(Object obj);
}


public interface Constraint {
    public Tuple get
}

public interface PrimaryKeyConstraint extends Constraint {
}

public interface ForeignKeyConstraint extends Constraint {
}

public interface UniqueConstraint extends Constraint {
}

Inheritance Tree for Tuple and Cursor

interface Tuple					// columns, qualifier	
  class TupleImpl

interface Cursor extends Tuple			// rows and movement
  abstract class CursorImpl extends TupleImpl implements Cursor
    class JoinCursor extends CursorImpl

interface Relation extends Tuple		// constraints, cursor mgmt
  class View extends TupleImpl implements Relation
  class Table extends TupleImpl implements Relation

Cursor
  CursorImpl
    Filter
      Aggregate
      Distinct
      GroupBy
      Having
      Predicate
    Index
    Items
    JoinCross
    JoinInner
    Merge
    OrderBy
    Static
    View

Table Expressions:
  Updatable
    SelectFromTable
  NonUpdatable
    JoinedTable
    MergeExpression
    VectorExpression (table value constructor)
  Possibly updatable
    SelectFromItem

TreeNode
  ClassOrInterfaceDef
    ClassDef
    interfaceDef
  Decl
    VariableDecl
    MethodDecl
    InnerClassDecl
    StaticBlockDecl
  Literal

Logging and recovery

Write-ahead logging
  Log entries:
    redo
    undo
    redo/undo
    CLR written when performing partial rollback
    begintransaction
    commit
    checkpoint

Recovery: redo, then undo
  Restore from last checkpoint.
  Redo all records from that point to the end of the log.
  Undo all loser transactions.

Checkpoint:
  Periodically, or at connection close, take checkpoint.
    Copy entire datafile
      Can optimize with 'modified pages' bitmap
    Compress log.
      Only save log records for pending uncommited transactions.

Join operations:

Break where clause down into "exp AND exp AND ..." form.
For each expression, classify it as one of:
  - table vs table (t1.fld == t2.fld)
  - table vs const (t1.fld == val)

All tables that don't appear in table vs table expressions go first in
the join order.

Tables that don't have any constant expressions go last in the join order.

All tables are joined using nested loops joins.  

Join over columns
  Natural (inner, left, right, full), Union
  Using : inner, left, right, full
Join on expression
  Cross
  On : inner, left, right, full

Dimensions
1. Number of tables
2. Number of columns
3. Datatypes
4. Field sizes
5. Integrity violations, statement rollback
6. Transaction rollback 
7. Views
8. Join, union, intersection, subquery,

• columns
• cross-reference
• indexes
• primary keys
• tables
• table types
• types

• SQL Loader
• XML Dump
• XML Load