pack-priv abstract Class SingleChildResultSetNode

Overrides org.apache.derby.impl.sql.compile.FromTable.acceptChildren.

Accept the visitor for all visitable children of this node.

Parameters

v:Visitor

the visitor

Annotations

@Override

Exceptions

StandardException:

on error

Overrides org.apache.derby.impl.sql.compile.ResultSetNode.addNewPredicate.

Add a new predicate to the list. This is useful when doing subquery transformations, when we build a new predicate with the left side of the subquery operator and the subquery's result column.

Parameters

predicate:Predicate

The predicate to add

Returns:ResultSetNode

ResultSetNode The new top of the tree.

Annotations

@Override

Exceptions

StandardException:

Thrown on error

Overrides org.apache.derby.impl.sql.compile.ResultSetNode.adjustForSortElimination.

Doc from org.apache.derby.impl.sql.compile.ResultSetNode.adjustForSortElimination.

Notify the underlying result set tree that the optimizer has chosen to "eliminate" a sort. Sort elimination can happen as part of preprocessing (see esp. SelectNode.preprocess(...)) or it can happen if the optimizer chooses an access path that inherently returns the rows in the correct order (also known as a "sort avoidance" plan). In either case we drop the sort and rely on the underlying result set tree to return its rows in the correct order. For most types of ResultSetNodes we automatically get the rows in the correct order if the sort was eliminated. One exception to this rule, though, is the case of an IndexRowToBaseRowNode, for which we have to disable bulk fetching on the underlying base table. Otherwise the index scan could return rows out of order if the base table is updated while the scan is "in progress" (i.e. while the result set is open). In order to account for this (and potentially other, similar issues in the future) this method exists to notify the result set node that it is expected to return rows in the correct order. The result set can then take necessary action to satsify this requirement--such as disabling bulk fetch in the case of IndexRowToBaseRowNode. All of that said, any ResultSetNodes for which we could potentially eliminate sorts should override this method accordingly. So we don't ever expect to get here.

Annotations

@Override

See Also

ResultSetNode#adjustForSortElimination

Overrides org.apache.derby.impl.sql.compile.ResultSetNode.adjustForSortElimination.

Doc from org.apache.derby.impl.sql.compile.ResultSetNode.adjustForSortElimination.

Same goal as adjustForSortElimination above, but this version takes a RequiredRowOrdering to allow nodes to adjust based on the ORDER BY clause, if needed.

Annotations

@Override

See Also

ResultSetNode#adjustForSortElimination

Overrides org.apache.derby.impl.sql.compile.ResultSetNode.changeAccessPath.

Doc from org.apache.derby.impl.sql.compile.ResultSetNode.changeAccessPath.

The optimizer's decision on the access path for a result set may require the generation of extra result sets. For example, if it chooses an index for a FromBaseTable, we need an IndexToBaseRowNode above the FromBaseTable (and the FromBaseTable has to change its column list to match the index. This method in the parent class does not generate any extra result sets. It may be overridden in child classes.

Returns:ResultSetNode

A ResultSetNode tree modified to do any extra processing for the chosen access path

Annotations

@Override

Exceptions

StandardException:

Thrown on error

See Also

ResultSetNode#changeAccessPath

Overrides org.apache.derby.impl.sql.compile.FromTable.decrementLevel.

Decrement (query block) level (0-based) for this FromTable. This is useful when flattening a subquery.

Parameters

decrement:int

The amount to decrement by.

Annotations

@Override

Overrides org.apache.derby.impl.sql.compile.ResultSetNode.ensurePredicateList.

Ensure that the top of the RSN tree has a PredicateList.

Parameters

numTables:int

The number of tables in the query.

Returns:ResultSetNode

ResultSetNode A RSN tree with a node which has a PredicateList on top.

Annotations

@Override

Exceptions

StandardException:

Thrown on error

Overrides org.apache.derby.impl.sql.compile.ResultSetNode.flattenableInFromSubquery.

Evaluate whether or not the subquery in a FromSubquery is flattenable. Currently, a FSqry is flattenable if all of the following are true: o Subquery is a SelectNode. o It contains no top level subqueries. (RESOLVE - we can relax this) o It does not contain a group by or having clause o It does not contain aggregates.

Parameters

fromList:FromList

The outer from list

Returns:boolean

boolean Whether or not the FromSubquery is flattenable.

Annotations

@Override

Return the childResult from this node.

Returns:ResultSetNode

ResultSetNode The childResult from this node.

Overrides org.apache.derby.impl.sql.compile.FromTable.getFinalCostEstimate.

Get the final CostEstimate for this node.

Returns:CostEstimate

The final CostEstimate for this node, which is the final cost estimate for the child node.

Annotations

@Override

Overrides org.apache.derby.impl.sql.compile.FromTable.getFromTableByName.

Determine whether or not the specified name is an exposed name in the current query block.

Parameters

name:String

The specified name to search for as an exposed name.

schemaName:String

Schema name, if non-null.

exactMatch:boolean

Whether or not we need an exact match on specified schema and table names or match on table id.

Returns:FromTable

The FromTable, if any, with the exposed name.

Annotations

@Override

Exceptions

StandardException:

Thrown on error

Overrides org.apache.derby.impl.sql.compile.ResultSetNode.isNotExists.

Return whether or not the underlying ResultSet tree is for a NOT EXISTS join.

Returns:boolean

Whether or not the underlying ResultSet tree is for a NOT EXISTS.

Annotations

@Override

Overrides org.apache.derby.impl.sql.compile.ResultSetNode.isOneRowResultSet.

Return whether or not the underlying ResultSet tree will return a single row, at most. This is important for join nodes where we can save the extra next on the right side if we know that it will return at most 1 row.

Returns:boolean

Whether or not the underlying ResultSet tree will return a single row.

Annotations

@Override

Exceptions

StandardException:

Thrown on error

Overrides org.apache.derby.impl.sql.compile.ResultSetNode.isOrderedOn.

Return whether or not the underlying ResultSet tree is ordered on the specified columns. RESOLVE - This method currently only considers the outermost table of the query block.

Parameters

crs:ColumnReference[]

The specified ColumnReference[]

permuteOrdering:boolean

Whether or not the order of the CRs in the array can be permuted

fbtHolder:List<FromBaseTable>

List that is to be filled with the FromBaseTable

Returns:boolean

Whether the underlying ResultSet tree is ordered on the specified column.

Annotations

@Override

Exceptions

StandardException:

Thrown on error

Overrides org.apache.derby.impl.sql.compile.ResultSetNode.modifyAccessPaths.

Doc from org.apache.derby.impl.sql.compile.ResultSetNode.modifyAccessPaths.

Modify the access paths according to the decisions the optimizer made. This can include adding project/restrict nodes, index-to-base-row nodes, etc.

Returns:ResultSetNode

The modified query tree

Annotations

@Override

Exceptions

StandardException:

Thrown on error

See Also

ResultSetNode#modifyAccessPaths

Overrides org.apache.derby.impl.sql.compile.ResultSetNode.optimize.

Optimize this SingleChildResultSetNode.

Parameters

dataDictionary:DataDictionary

The DataDictionary to use for optimization

predicates:PredicateList

The PredicateList to optimize. This should be a join predicate.

outerRows:double

The number of outer joining rows

Returns:ResultSetNode

ResultSetNode The top of the optimized subtree

Annotations

@Override

Exceptions

StandardException:

Thrown on error

Overrides org.apache.derby.impl.sql.compile.ResultSetNode.preprocess.

Put a ProjectRestrictNode on top of each FromTable in the FromList. ColumnReferences must continue to point to the same ResultColumn, so that ResultColumn must percolate up to the new PRN. However, that ResultColumn will point to a new expression, a VirtualColumnNode, which points to the FromTable and the ResultColumn that is the source for the ColumnReference. (The new PRN will have the original of the ResultColumnList and the ResultColumns from that list. The FromTable will get shallow copies of the ResultColumnList and its ResultColumns. ResultColumn.expression will remain at the FromTable, with the PRN getting a new VirtualColumnNode for each ResultColumn.expression.) We then project out the non-referenced columns. If there are no referenced columns, then the PRN's ResultColumnList will consist of a single ResultColumn whose expression is 1.

Parameters

numTables:int

Number of tables in the DML Statement

gbl:GroupByList

The group by list, if any

fromList:FromList

The from list, if any

Returns:ResultSetNode

The generated ProjectRestrictNode atop the original FromTable.

Annotations

@Override

Exceptions

StandardException:

Thrown on error

Overrides org.apache.derby.impl.sql.compile.ResultSetNode.printSubNodes.

Prints the sub-nodes of this object. See QueryTreeNode.java for how tree printing is supposed to work.

Parameters

depth:int

The depth of this node in the tree

Annotations

@Override

Overrides org.apache.derby.impl.sql.compile.FromTable.pushExpressions.

Push expressions down to the first ResultSetNode which can do expression evaluation and has the same referenced table map. RESOLVE - This means only pushing down single table expressions to DistinctNodes today. Once we have a better understanding of how the optimizer will work, we can push down join clauses.

Parameters

predicateList:PredicateList

The PredicateList.

Annotations

@Override

Exceptions

StandardException:

Thrown on error

Overrides org.apache.derby.impl.sql.compile.ResultSetNode.referencesTarget.

Search to see if a query references the specifed table name.

Parameters

name:String

Table name (String) to search for.

baseTable:boolean

Whether or not name is for a base table

Returns:boolean

true if found, else false

Annotations

@Override

Exceptions

StandardException:

Thrown on error

Set the childResult for this node.

Parameters

childResult:ResultSetNode

The new childResult for this node.

Overrides org.apache.derby.impl.sql.compile.FromTable.setLevel.

Set the (query block) level (0-based) for this FromTable.

Parameters

level:int

The query block level for this FromTable.

Annotations

@Override

Overrides org.apache.derby.impl.sql.compile.ResultSetNode.subqueryReferencesTarget.

Return whether or not this ResultSetNode contains a subquery with a reference to the specified target.

Parameters

name:String

The table name.

baseTable:boolean

Whether or not the name is for a base table.

Returns:boolean

boolean Whether or not a reference to the table was found.

Annotations

@Override

Exceptions

StandardException:

Thrown on error

Overrides org.apache.derby.impl.sql.compile.ResultSetNode.updateTargetLockMode.

Get the lock mode for the target of an update statement (a delete or update). The update mode will always be row for CurrentOfNodes. It will be table if there is no where clause.

Returns:int

The lock mode

Annotations

@Override