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## org.modeshape.graph.query.plan
Class CanonicalPlanner

    java.lang.Object
      org.modeshape.graph.query.plan.CanonicalPlanner

All Implemented Interfaces:
  Planner

    public class CanonicalPlanner

extends Object
implements Planner

The planner that produces a canonical query plan given a `query command`.

A canonical plan always has the same structure:

           LIMIT       if row limit or offset are used
             |
          SORTING      if 'ORDER BY' is used
             |
         DUP_REMOVE    if 'SELECT DISTINCT' is used
             |
          PROJECT      with the list of columns being SELECTed
             |
           GROUP       if 'GROUP BY' is used
             |
          SELECT1
             |         One or more SELECT plan nodes that each have
          SELECT2      a single non-join constraint that are then all AND-ed
             |         together (see separateAndConstraints(Constraint, List))
          SELECTn
             |
        SOURCE or JOIN     A single SOURCE or JOIN node, depending upon the query
                  /  \
                 /    \
               SOJ    SOJ    A SOURCE or JOIN node for the left and right side of the JOIN

There leaves of the tree are always SOURCE nodes, so conceptually data always flows through this plan from the bottom SOURCE nodes, is adjusted/filtered as it trickles up through the plan, and is then ready to be used by the caller as it emerges from the top node of the plan.

This canonical plan, however, is later optimized and rearranged so that it performs faster.

Constructor Summary
`CanonicalPlanner()`

Method Summary
`protected void` | `allColumnsFor(Schemata.Table table, SelectorName tableName, List<Column> columns, List<String> columnTypes)`
`protected PlanNode` | `attachCriteria(QueryContext context, PlanNode plan, Constraint constraint, List<? extends Column> columns, Map<String,Subquery> subqueriesByVariableName)` Attach all criteria above the join nodes.
`protected PlanNode` | `attachDuplicateRemoval(QueryContext context, PlanNode plan)` Attach DUP_REMOVE node at top of tree.
`protected PlanNode` | `attachLimits(QueryContext context, PlanNode plan, Limit limit)` Attach a LIMIT node at the top of the plan tree.
`protected PlanNode` | `attachProject(QueryContext context, PlanNode plan, List<? extends Column> columns, Map<SelectorName,Schemata.Table> selectors)` Attach a PROJECT node at the top of the plan tree.
`protected PlanNode` | `attachSorting(QueryContext context, PlanNode plan, List<? extends Ordering> orderings)` Attach SORT node at top of tree.
`protected PlanNode` | `attachSubqueries(QueryContext context, PlanNode plan, Map<String,Subquery> subqueriesByVariableName)` Attach plan nodes for each subquery, resulting with the first subquery at the top of the plan tree.
`protected PlanNode` | `createCanonicalPlan(QueryContext context, Query query)` Create a canonical query plan for the given query.
`protected PlanNode` | `createCanonicalPlan(QueryContext context, SetQuery query)` Create a canonical query plan for the given set query.
`PlanNode` | `createPlan(QueryContext context, QueryCommand query)` Create a canonical query plan for the given command.
`protected PlanNode` | `createPlanNode(QueryContext context, Source source, Map<SelectorName,Schemata.Table> usedSelectors)` Create a JOIN or SOURCE node that contain the source information.
`protected void` | `separateAndConstraints(Constraint constraint, List<Constraint> andableConstraints)` Walk the supplied constraint to extract a list of the constraints that can be AND-ed together.
`protected void` | `setSubqueryVariableName(PlanNode subqueryPlan, String varName)`
`protected void` | `validate(QueryContext context, QueryCommand query, Map<SelectorName,Schemata.Table> usedSelectors)` Validate the supplied query.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### CanonicalPlanner

    public CanonicalPlanner()

Method Detail

### createPlan

    public PlanNode createPlan(QueryContext context,
                               QueryCommand query)

  Create a canonical query plan for the given command.

  Specified by:
    `createPlan` in interface `Planner`
  Parameters:
    `context` - the context in which the query is being planned
    `query` - the query command to be planned
  Returns:
    the root node of the plan tree representing the canonical plan
  See Also:
    `Planner.createPlan(org.modeshape.graph.query.QueryContext, org.modeshape.graph.query.model.QueryCommand)`

### createCanonicalPlan

    protected PlanNode createCanonicalPlan(QueryContext context,
                                           Query query)

  Create a canonical query plan for the given query.

  Parameters:
    `context` - the context in which the query is being planned
    `query` - the query to be planned
  Returns:
    the root node of the plan tree representing the canonical plan

### validate

    protected void validate(QueryContext context,
                            QueryCommand query,
                            Map<SelectorName,Schemata.Table> usedSelectors)

  Validate the supplied query.

  Parameters:
    `context` - the context in which the query is being planned
    `query` - the set query to be planned
    `usedSelectors` - the map of `SelectorName`s (aliases or names) used in the query.

### createCanonicalPlan

    protected PlanNode createCanonicalPlan(QueryContext context,
                                           SetQuery query)

  Create a canonical query plan for the given set query.

  Parameters:
    `context` - the context in which the query is being planned
    `query` - the set query to be planned
  Returns:
    the root node of the plan tree representing the canonical plan

### createPlanNode

    protected PlanNode createPlanNode(QueryContext context,
                                      Source source,
                                      Map<SelectorName,Schemata.Table> usedSelectors)

  Create a JOIN or SOURCE node that contain the source information.

  Parameters:
    `context` - the execution context
    `source` - the source to be processed; may not be null
    `usedSelectors` - the map of `SelectorName`s (aliases or names) used in the query.
  Returns:
    the new plan; never null

### attachCriteria

    protected PlanNode attachCriteria(QueryContext context,
                                      PlanNode plan,
                                      Constraint constraint,
                                      List<? extends Column> columns,
                                      Map<String,Subquery> subqueriesByVariableName)

  Attach all criteria above the join nodes. The optimizer will push these criteria down to the appropriate source.

  Parameters:
    `context` - the context in which the query is being planned
    `plan` - the existing plan, which joins all source groups
    `constraint` - the criteria or constraint from the query
    `columns` - the columns in the select (that may have aliases)
    `subqueriesByVariableName` - the subqueries by variable name
  Returns:
    the updated plan, or the existing plan if there were no constraints; never null

### separateAndConstraints

    protected void separateAndConstraints(Constraint constraint,
                                          List<Constraint> andableConstraints)

  Walk the supplied constraint to extract a list of the constraints that can be AND-ed together. For example, given the constraint tree ((C1 AND C2) AND (C3 OR C4)), this method would result in a list of three separate criteria: [C1,C2,(C3 OR C4)]. The resulting `andConstraints` list will contain Constraint objects that all must be true.

  Parameters:
    `constraint` - the input constraint
    `andableConstraints` - the collection into which all non-`AND` constraints should be placed

### attachSorting

    protected PlanNode attachSorting(QueryContext context,
                                     PlanNode plan,
                                     List<? extends Ordering> orderings)

  Attach SORT node at top of tree. The SORT may be pushed down to a source (or sources) if possible by the optimizer.

  Parameters:
    `context` - the context in which the query is being planned
    `plan` - the existing plan
    `orderings` - list of orderings from the query
  Returns:
    the updated plan, or the existing plan if there were no orderings; never null

### attachLimits

    protected PlanNode attachLimits(QueryContext context,
                                    PlanNode plan,
                                    Limit limit)

  Attach a LIMIT node at the top of the plan tree.

  Parameters:
    `context` - the context in which the query is being planned
    `plan` - the existing plan
    `limit` - the limit definition; may be null
  Returns:
    the updated plan, or the existing plan if there were no limits

### attachProject

    protected PlanNode attachProject(QueryContext context,
                                     PlanNode plan,
                                     List<? extends Column> columns,
                                     Map<SelectorName,Schemata.Table> selectors)

  Attach a PROJECT node at the top of the plan tree.

  Parameters:
    `context` - the context in which the query is being planned
    `plan` - the existing plan
    `columns` - the columns being projected; may be null
    `selectors` - the selectors keyed by their alias or name
  Returns:
    the updated plan

### allColumnsFor

    protected void allColumnsFor(Schemata.Table table,
                                 SelectorName tableName,
                                 List<Column> columns,
                                 List<String> columnTypes)

### attachDuplicateRemoval

    protected PlanNode attachDuplicateRemoval(QueryContext context,
                                              PlanNode plan)

  Attach DUP_REMOVE node at top of tree. The DUP_REMOVE may be pushed down to a source (or sources) if possible by the optimizer.

  Parameters:
    `context` - the context in which the query is being planned
    `plan` - the existing plan
  Returns:
    the updated plan

### attachSubqueries

    protected PlanNode attachSubqueries(QueryContext context,
                                        PlanNode plan,
                                        Map<String,Subquery> subqueriesByVariableName)

  Attach plan nodes for each subquery, resulting with the first subquery at the top of the plan tree.

  Parameters:
    `context` - the context in which the query is being planned
    `plan` - the existing plan
    `subqueriesByVariableName` - the queries by the variable name used in substitution
  Returns:
    the updated plan, or the existing plan if there were no limits

### setSubqueryVariableName

    protected void setSubqueryVariableName(PlanNode subqueryPlan,
                                           String varName)

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