mondrian.rolap.agg
Class SegmentLoader

java.lang.Object
  mondrian.rolap.agg.SegmentLoader

public class SegmentLoader
extends Object

The SegmentLoader queries database and loads the data into the given set of segments.

It reads a segment of measure, where columns are constrained to values. Each entry in values can be null, meaning don't constrain, or can have several values. For example, getSegment({Unit_sales}, {Region, State, Year}, {"West"}, {"CA", "OR", "WA"}, null}) returns sales in states CA, OR and WA in the Western region, for all years.

It will also look at the MondrianProperties.SegmentCache property and make usage of the SegmentCache provided as an SPI.

Since:

24 May 2007

Author:

Thiyagu, LBoudreau

Nested Class Summary

protected static class	SegmentLoader.RowList Collection of rows, each with a set of columns of type Object, double, or int.
(package private) class	SegmentLoader.SegmentRollupWrapper This is a private abstraction wrapper to perform rollups.

Constructor Summary

SegmentLoader(SegmentCacheManager cacheMgr)
Creates a SegmentLoader.

Method Summary

(package private) SqlStatement	createExecuteSql(int cellRequestCount, GroupingSetsList groupingSetsList, List<StarPredicate> compoundPredicateList) Creates and executes a SQL statement to retrieve the set of cells specified by a GroupingSetsList.
(package private) SortedSet<Comparable>[]	getDistinctValueWorkspace(int arity)
(package private) BitKey	getRollupBitKey(int arity, ResultSet rowList, int k) Generates bit key representing roll up columns
void	load(int cellRequestCount, List<GroupingSet> groupingSets, List<StarPredicate> compoundPredicateList, List<Future<Map<Segment,SegmentWithData>>> segmentFutures) Loads data for all the segments of the GroupingSets.
(package private) ResultSet	loadData(SqlStatement stmt, GroupingSetsList groupingSetsList)
(package private) SegmentLoader.RowList	processData(SqlStatement stmt, boolean[] axisContainsNull, SortedSet<Comparable>[] axisValueSets, GroupingSetsList groupingSetsList)
(package private) boolean	useSparse(boolean sparse, int n, SegmentLoader.RowList rows)
(package private) static boolean	useSparse(double possibleCount, double actualCount) Decides whether to use a sparse representation for this segment, using the formula described here.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SegmentLoader

public SegmentLoader(SegmentCacheManager cacheMgr)

Creates a SegmentLoader.

Parameters:

cacheMgr - Cache manager

Method Detail

load

public void load(int cellRequestCount,
                 List<GroupingSet> groupingSets,
                 List<StarPredicate> compoundPredicateList,
                 List<Future<Map<Segment,SegmentWithData>>> segmentFutures)

Loads data for all the segments of the GroupingSets. If the grouping sets list contains more than one Grouping Set then data is loaded using the GROUP BY GROUPING SETS sql. Else if only one grouping set is passed in the list data is loaded without using GROUP BY GROUPING SETS sql. If the database does not support grouping sets Dialect.supportsGroupingSets() then grouping sets list should always have only one element in it.

For example, if list has 2 grouping sets with columns A, B, C and B, C respectively, then the SQL will be "GROUP BY GROUPING SETS ((A, B, C), (B, C))".

Else if the list has only one grouping set then sql would be without grouping sets.

The groupingSets list should be topological order, with more detailed higher-level grouping sets occurring first. In other words, the first element of the list should always be the detailed grouping set (default grouping set), followed by grouping sets which can be rolled-up on this detailed grouping set. In the example (A, B, C) is the detailed grouping set and (B, C) is rolled-up using the detailed.

Grouping sets are removed from the groupingSets list as they are loaded.

Parameters:

cellRequestCount - Number of missed cells that led to this request

groupingSets - List of grouping sets whose segments are loaded

compoundPredicateList - Compound predicates

segmentFutures - List of futures wherein each statement will place a list of the segments it has loaded, when it completes

useSparse

boolean useSparse(boolean sparse,
                  int n,
                  SegmentLoader.RowList rows)

createExecuteSql

SqlStatement createExecuteSql(int cellRequestCount,
                              GroupingSetsList groupingSetsList,
                              List<StarPredicate> compoundPredicateList)

Creates and executes a SQL statement to retrieve the set of cells specified by a GroupingSetsList.

This method may be overridden in tests.

Parameters:

cellRequestCount - Number of missed cells that led to this request

groupingSetsList - Grouping

compoundPredicateList - Compound predicate list

Returns:

An executed SQL statement, or null

processData

SegmentLoader.RowList processData(SqlStatement stmt,
                                  boolean[] axisContainsNull,
                                  SortedSet<Comparable>[] axisValueSets,
                                  GroupingSetsList groupingSetsList)
                            throws SQLException

Throws:

SQLException

getRollupBitKey

BitKey getRollupBitKey(int arity,
                       ResultSet rowList,
                       int k)
                 throws SQLException

Generates bit key representing roll up columns

Throws:

SQLException

loadData

ResultSet loadData(SqlStatement stmt,
                   GroupingSetsList groupingSetsList)
             throws SQLException

Throws:

SQLException

getDistinctValueWorkspace

SortedSet<Comparable>[] getDistinctValueWorkspace(int arity)

useSparse

static boolean useSparse(double possibleCount,
                         double actualCount)

Decides whether to use a sparse representation for this segment, using the formula described here.

Parameters:

possibleCount - Number of values in the space.

actualCount - Actual number of values.

Returns:

Whether to use a sparse representation.