com.lucidera.lcs
Class LcsTableMergeRule

java.lang.Object
  org.eigenbase.relopt.RelOptRule
      com.lucidera.lcs.LcsTableMergeRule

public class LcsTableMergeRule
extends RelOptRule

LcsTableMergeRule is a rule for converting an abstract TableModificationRel into a corresponding LcsTableMergeRel.

Version:

$Id: //open/dev/farrago/src/com/lucidera/lcs/LcsTableMergeRule.java#21 $

Author:

Zelaine Fong

Field Summary

private static double	COLUMN_UPDATE_THRESHOLD The upper bound on the percentage of columns that must be updated for the replace column optimization to be used
static LcsTableMergeRule	instance
private static double	ROW_UPDATE_THRESHOLD The lower bound on the percentage of rows that must be updated for the replace column optimization to be used.
private static Logger	tracer

Fields inherited from class org.eigenbase.relopt.RelOptRule

ANY, description, operands

Constructor Summary

private

LcsTableMergeRule() Creates a LcsTableMergeRule.

Method Summary

private List<FemLocalIndex>	checkSingleColClusters(List<String> updateCols, LcsTable table, FarragoRepos repos) Determines if each of the columns from a list of columns being updated all belong to clusters containing only a single column.
private boolean	checkUniqueJoinKeys(JoinRel joinRel) Determines if the join keys corresponding to the source for the MERGE are unique.
private RelNode	createChangeFilterRel(ProjectRel origProj, RelDataTypeField[] targetFields, List<String> updateList, boolean updateOnly, RexNode ridExpr, RexBuilder rexBuilder, int nInsertFields) Creates the filter expression used to detect changed rows.
private RelNode	createInsertSource(ProjectRel origProj, RelDataTypeField[] targetFields, RexNode ridExpr, RexBuilder rexBuilder) Creates a RelNode that serves as the source for an insert-only MERGE.
private void	createNullFilter(RexBuilder rexBuilder, RexNode expr, List<RexNode> filterList) Creates an is null expression on an expression and adds it to a list of filters
private RelNode	createUpdateSource(ProjectRel origProj, RelDataTypeField[] targetFields, List<String> updateList, boolean updateOnly, boolean replaceColumns, RexNode ridExpr, RexBuilder rexBuilder) Creates the source RelNode for a MERGE that contains an UPDATE component.
CallingConvention	getOutConvention() Returns the calling convention of the result of firing this rule, null if not known.
void	onMatch(RelOptRuleCall call) Receives notification about a rule match.
(package private) List<FemLocalIndex>	shouldReplaceColumns(LcsTable target, JoinRel source, List<String> updateCols, boolean updateOnly) Determines whether the merge should be executed by replacing the columns being updated, as opposed to updating individual rows.

Methods inherited from class org.eigenbase.relopt.RelOptRule

convert, equals, equals, getOperand, getOperands, getOutTrait, hashCode, matches, mergeTraitsAndConvert, mergeTraitsAndConvert, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

tracer

private static final Logger tracer

COLUMN_UPDATE_THRESHOLD

private static final double COLUMN_UPDATE_THRESHOLD

The upper bound on the percentage of columns that must be updated for the replace column optimization to be used

See Also:

Constant Field Values

ROW_UPDATE_THRESHOLD

private static final double ROW_UPDATE_THRESHOLD

The lower bound on the percentage of rows that must be updated for the replace column optimization to be used. Note that this percentage will be multiplied by the percentage of columns updated by the statement, so the threshold is lower when fewer columns are updated.

See Also:

Constant Field Values

instance

public static final LcsTableMergeRule instance

Constructor Detail

LcsTableMergeRule

private LcsTableMergeRule()

Creates a LcsTableMergeRule.

Method Detail

getOutConvention

public CallingConvention getOutConvention()

Description copied from class: RelOptRule

Returns the calling convention of the result of firing this rule, null if not known.

Overrides:

getOutConvention in class RelOptRule

onMatch

public void onMatch(RelOptRuleCall call)

Description copied from class: RelOptRule

Receives notification about a rule match. At the time that this method is called, call.rels holds the set of relational expressions which match the operands to the rule; call.rels[0] is the root expression.

Typically a rule would check that the nodes are valid matches, creates a new expression, then calls back RelOptRuleCall.transformTo(org.eigenbase.rel.RelNode) to register the expression.

Specified by:

onMatch in class RelOptRule

Parameters:

call - Rule call

See Also:

RelOptRule.matches(RelOptRuleCall)

shouldReplaceColumns

List<FemLocalIndex> shouldReplaceColumns(LcsTable target,
                                         JoinRel source,
                                         List<String> updateCols,
                                         boolean updateOnly)

Determines whether the merge should be executed by replacing the columns being updated, as opposed to updating individual rows. This is only feasible if:

1. The underlying personality supports snapshots.
2. The merge statement only contains an update substatement.
3. The columns being updated all correspond to single column clusters.
4. The keys in the ON condition are unique.
5. The number of columns being updated is less than some threshold.
6. The percentage of rows being updated is greater than a threshold that also depends on the percentage of columns updated.

Parameters:

target - the target table

source - the source for the merge

updateCols - list of columns being updated

updateOnly - true if the statement only contains an update substatement

Returns:

list of clusters corresponding to the columns being updated if the criteria are met; otherwise, null

checkUniqueJoinKeys

private boolean checkUniqueJoinKeys(JoinRel joinRel)

Determines if the join keys corresponding to the source for the MERGE are unique. Rid expressions are considered to be unique keys.

Parameters:

joinRel - the join

Returns:

true if the join keys are unique

checkSingleColClusters

private List<FemLocalIndex> checkSingleColClusters(List<String> updateCols,
                                                   LcsTable table,
                                                   FarragoRepos repos)

Determines if each of the columns from a list of columns being updated all belong to clusters containing only a single column.

Parameters:

updateCols - the list of columns being updated

table - the target table

repos - repository

Returns:

the clusters corresponding to the columns being updated in an order matching the update columns, provided the columns are all part of single-column clusters; otherwise, null is returned

createInsertSource

private RelNode createInsertSource(ProjectRel origProj,
                                   RelDataTypeField[] targetFields,
                                   RexNode ridExpr,
                                   RexBuilder rexBuilder)

Creates a RelNode that serves as the source for an insert-only MERGE. A FilterRel is inserted underneath the current ProjectRel. The filter removes rids that are non-null.

Parameters:

origProj - original projection

targetFields - fields from the target table

ridExpr - expression representing the target rid column

rexBuilder - rex builder

Returns:

RelNode corresponding to the source for the insert-only MERGE

createUpdateSource

private RelNode createUpdateSource(ProjectRel origProj,
                                   RelDataTypeField[] targetFields,
                                   List<String> updateList,
                                   boolean updateOnly,
                                   boolean replaceColumns,
                                   RexNode ridExpr,
                                   RexBuilder rexBuilder)

Creates the source RelNode for a MERGE that contains an UPDATE component. The current ProjectRel is replaced by a FilterRel underneath a new ProjectRel. The filter removes rows where the columns are not actually updated.

The new projection projects the target rid followed by a set of expressions representing new insert rows, or in the case where columns are being replaced, the replaced column values.

Parameters:

origProj - the original projection being replaced

targetFields - fields from the target table

updateList - list of names corresponding to the update columns

updateOnly - if true, MERGE statement contains no INSERT

replaceColumns - true if the MERGE will be executed by replacing entire columns

ridExpr - expression representing the target rid column

rexBuilder - rex builder

Returns:

source RelNode for a MERGE that contains an UPDATE

createChangeFilterRel

private RelNode createChangeFilterRel(ProjectRel origProj,
                                      RelDataTypeField[] targetFields,
                                      List<String> updateList,
                                      boolean updateOnly,
                                      RexNode ridExpr,
                                      RexBuilder rexBuilder,
                                      int nInsertFields)

Creates the filter expression used to detect changed rows. The expression looks like (ROW(O1, O2, ...) IS DISTINCT FROM ROW(N1, N2, ...)) where the O references are the old values and the N references are the new values. We rely on a custom implementation of the row-wise IS DISTINCT FROM operator in the Java calc to evaluate this efficiently and without exceeding the Java calc limit on method bytecode size. (As opposed to RelOptUtil.isDistinctFrom(org.eigenbase.rex.RexBuilder, org.eigenbase.rex.RexNode, org.eigenbase.rex.RexNode, boolean), which generates a deeply nested tree.)

Parameters:

origProj - the original projection being replaced

targetFields - fields from the target table

updateList - list of names corresponding to the update columns

updateOnly - if true, MERGE statement contains no INSERT

ridExpr - expression representing the target rid column

rexBuilder - rex builder

nInsertFields - number of fields in INSERT portion of UPSERT

Returns:

filter rel

createNullFilter

private void createNullFilter(RexBuilder rexBuilder,
                              RexNode expr,
                              List<RexNode> filterList)

Creates an is null expression on an expression and adds it to a list of filters

Parameters:

rexBuilder - rex builder

expr - expression to create the is null expression on

filterList - list of filters