org.apache.derby.impl.sql.compile

Class CursorNode

java.lang.Object

org.apache.derby.impl.sql.compile.QueryTreeNode

org.apache.derby.impl.sql.compile.StatementNode

org.apache.derby.impl.sql.compile.DMLStatementNode

org.apache.derby.impl.sql.compile.CursorNode

All Implemented Interfaces:

Node, Visitable

public class CursorNode
extends DMLStatementNode

A CursorNode represents a result set that can be returned to a client. A cursor can be a named cursor created by the DECLARE CURSOR statement, or it can be an unnamed cursor associated with a SELECT statement (more precisely, a table expression that returns rows to the client). In the latter case, the cursor does not have a name.

Field Summary

Fields

Modifier and Type	Field and Description
private boolean	checkIndexStats
private ValueNode	fetchFirst
private boolean	hasJDBClimitClause
private int	indexOfSessionTableNamesInSavedObjects
private java.lang.String	name
private boolean	needTarget
private ValueNode	offset
private OrderByList	orderByList
static int	READ_ONLY
private java.lang.String	statementType
private java.util.ArrayList	statsToUpdate List of TableDescriptors for base tables whose associated indexes should be checked for stale statistics.
private ResultColumnDescriptor[]	targetColumnDescriptors
static int	UNSPECIFIED
private java.util.List	updatableColumns There can only be a list of updatable columns when FOR UPDATE is specified as part of the cursor specification.
static int	UPDATE
private int	updateMode
private FromTable	updateTable

Fields inherited from class org.apache.derby.impl.sql.compile.DMLStatementNode

resultSet

Fields inherited from class org.apache.derby.impl.sql.compile.StatementNode

EMPTY_TD_LIST, NEED_CURSOR_ACTIVATION, NEED_DDL_ACTIVATION, NEED_NOTHING_ACTIVATION, NEED_PARAM_ACTIVATION, NEED_ROW_ACTIVATION

Fields inherited from class org.apache.derby.impl.sql.compile.QueryTreeNode

AUTOINCREMENT_CREATE_MODIFY, AUTOINCREMENT_INC_INDEX, AUTOINCREMENT_IS_AUTOINCREMENT_INDEX, AUTOINCREMENT_START_INDEX

Constructor Summary

Constructors

Constructor and Description
CursorNode()

Method Summary

Modifier and Type	Method and Description
(package private) void	acceptChildren(Visitor v) Accept the visitor for all visitable children of this node.
(package private) int	activationKind() Returns the type of activation this class generates.
void	bindStatement() Bind this CursorNode.
private void	bindUpdateColumns(FromTable targetTable) Bind the update columns by their names to the target table of the cursor specification.
private void	collectTablesWithPossiblyStaleStats() Collects table descriptors for base tables whose index statistics we want to check for staleness (or to create).
private int	determineUpdateMode(DataDictionary dataDictionary) Take a cursor and determine if it is UPDATE or READ_ONLY based on the shape of the cursor specification.
void	generate(ActivationClassBuilder acb, MethodBuilder mb) Do code generation for this CursorNode
private ResultColumnDescriptor[]	genTargetResultColList() Positioned update needs to know what the target result set looks like.
java.lang.Object	getCursorInfo() Get information about this cursor.
protected java.util.ArrayList	getSessionSchemaTableNamesForCursor()
private java.lang.String[]	getUpdatableColumns() Return String[] of names from the FOR UPDATE OF List
java.lang.String	getUpdateBaseTableName()
private java.lang.String[]	getUpdateColumnNames() Get an array of strings for each updatable column in this list.
java.lang.String	getUpdateExposedTableName()
int	getUpdateMode()
java.lang.String	getUpdateSchemaName()
java.lang.String	getXML()
void	init(java.lang.Object statementType, java.lang.Object resultSet, java.lang.Object name, java.lang.Object orderByList, java.lang.Object offset, java.lang.Object fetchFirst, java.lang.Object hasJDBClimitClause, java.lang.Object updateMode, java.lang.Object updatableColumns) Initializer for a CursorNode
boolean	needsSavepoint() Returns whether or not this Statement requires a set/clear savepoint around its execution.
void	optimizeStatement() Optimize a DML statement (which is the only type of statement that should need optimizing, I think).
void	printSubNodes(int depth) Prints the sub-nodes of this object.
boolean	referencesSessionSchema() Return true if the node references SESSION schema tables (temporary or permanent)
java.lang.String	statementToString()
java.lang.String	toString() Convert this object to a String.
TableDescriptor[]	updateIndexStatisticsFor() Returns a list of base tables for which the index statistics of the associated indexes should be updated.
private static java.lang.String	updateModeString(int updateMode) Support routine for translating an updateMode identifier to a String

Methods inherited from class org.apache.derby.impl.sql.compile.DMLStatementNode

bind, bindExpressions, bindExpressionsWithTables, bindResultSetsWithTables, bindTables, generateParameterValueSet, getPrivType, getResultSetNode, init, isAtomic, makeResultDescription

Methods inherited from class org.apache.derby.impl.sql.compile.StatementNode

executeSchemaName, executeStatementName, generate, getSPSName, lockTableForCompilation

Methods inherited from class org.apache.derby.impl.sql.compile.QueryTreeNode

accept, bindOffsetFetch, bindRowMultiSet, bindUserCatalogType, bindUserType, checkReliability, checkReliability, convertDefaultNode, createTypeDependency, debugFlush, debugPrint, disablePrivilegeCollection, formatNodeString, foundString, generateAuthorizeCheck, getBeginOffset, getClassFactory, getCompilerContext, getContextManager, getDataDictionary, getDependencyManager, getEndOffset, getExecutionFactory, getGenericConstantActionFactory, getIntProperty, getLanguageConnectionContext, getNodeFactory, getNodeType, getNullNode, getParameterTypes, getSchemaDescriptor, getSchemaDescriptor, getStatementType, getTableDescriptor, getTypeCompiler, init, init, init, init, init, init, init, init, init, init, init, init, isInstanceOf, isPrivilegeCollectionRequired, isSessionSchema, isSessionSchema, makeConstantAction, makeTableName, makeTableName, nodeHeader, orReliability, parseStatement, printLabel, resolveTableToSynonym, setBeginOffset, setContextManager, setEndOffset, setNodeType, setRefActionInfo, stackPrint, treePrint, treePrint, verifyClassExist

Methods inherited from class java.lang.Object

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

Field Detail

UNSPECIFIED

public static final int UNSPECIFIED

See Also:

Constant Field Values

READ_ONLY

public static final int READ_ONLY

See Also:

Constant Field Values

UPDATE

public static final int UPDATE

See Also:

Constant Field Values

name

private java.lang.String name

orderByList

private OrderByList orderByList

offset

private ValueNode offset

fetchFirst

private ValueNode fetchFirst

hasJDBClimitClause

private boolean hasJDBClimitClause

statementType

private java.lang.String statementType

updateMode

private int updateMode

needTarget

private boolean needTarget

updatableColumns

private java.util.List updatableColumns

There can only be a list of updatable columns when FOR UPDATE is specified as part of the cursor specification.

updateTable

private FromTable updateTable

targetColumnDescriptors

private ResultColumnDescriptor[] targetColumnDescriptors

statsToUpdate

private java.util.ArrayList statsToUpdate

List of TableDescriptors for base tables whose associated indexes should be checked for stale statistics.

checkIndexStats

private boolean checkIndexStats

indexOfSessionTableNamesInSavedObjects

private int indexOfSessionTableNamesInSavedObjects

Constructor Detail

CursorNode

public CursorNode()

Method Detail

init

public void init(java.lang.Object statementType,
                 java.lang.Object resultSet,
                 java.lang.Object name,
                 java.lang.Object orderByList,
                 java.lang.Object offset,
                 java.lang.Object fetchFirst,
                 java.lang.Object hasJDBClimitClause,
                 java.lang.Object updateMode,
                 java.lang.Object updatableColumns)

Initializer for a CursorNode

Specified by:

init in interface Node

Overrides:

init in class QueryTreeNode

Parameters:

statementType - Type of statement (SELECT, UPDATE, INSERT)

resultSet - A ResultSetNode specifying the result set for the cursor

name - The name of the cursor, null if no name

orderByList - The order by list for the cursor, null if no order by list

offset - The value of a if present

fetchFirst - The value of a if present

hasJDBClimitClause - True if the offset/fetchFirst clauses come from JDBC limit/offset escape syntax

updateMode - The user-specified update mode for the cursor, for example, CursorNode.READ_ONLY

updatableColumns - The list of updatable columns specified by the user in the FOR UPDATE clause, null if no updatable columns specified. May only be provided if the updateMode parameter is CursorNode.UPDATE.

toString

public java.lang.String toString()

Convert this object to a String. See comments in QueryTreeNode.java for how this should be done for tree printing.

Overrides:

toString in class StatementNode

Returns:

This object as a String

statementToString

public java.lang.String statementToString()

Specified by:

statementToString in class StatementNode

updateModeString

private static java.lang.String updateModeString(int updateMode)

Support routine for translating an updateMode identifier to a String

Parameters:

updateMode - An updateMode identifier

Returns:

A String representing the update mode.

printSubNodes

public void printSubNodes(int depth)

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

Overrides:

printSubNodes in class DMLStatementNode

Parameters:

depth - The depth of this node in the tree

bindStatement

public void bindStatement()
                   throws StandardException

Bind this CursorNode. This means looking up tables and columns and getting their types, and figuring out the result types of all expressions, as well as doing view resolution, permissions checking, etc. It also includes determining whether an UNSPECIFIED cursor is updatable or not, and verifying that an UPDATE cursor actually is.

Overrides:

bindStatement in class StatementNode

Throws:

StandardException - Thrown on error

collectTablesWithPossiblyStaleStats

private void collectTablesWithPossiblyStaleStats()
                                          throws StandardException

Collects table descriptors for base tables whose index statistics we want to check for staleness (or to create).

Throws:

StandardException

referencesSessionSchema

public boolean referencesSessionSchema()
                                throws StandardException

Return true if the node references SESSION schema tables (temporary or permanent)

Overrides:

referencesSessionSchema in class QueryTreeNode

Returns:

true if references SESSION schema tables, else false

Throws:

StandardException - Thrown on error

getSessionSchemaTableNamesForCursor

protected java.util.ArrayList getSessionSchemaTableNamesForCursor()
                                                           throws StandardException

Throws:

StandardException

determineUpdateMode

private int determineUpdateMode(DataDictionary dataDictionary)
                         throws StandardException

Take a cursor and determine if it is UPDATE or READ_ONLY based on the shape of the cursor specification.

The following conditions make a cursor read only:

• if it says FOR READ ONLY
• if it says ORDER BY
• if its query specification is not read only. At present this is explicitly tested here, with these conditions. At some future point in time, this checking ought to be moved into the ResultSet nodes themselves. The conditions for a query spec. not to be read only include:
  • if it has a set operation such as UNION or INTERSECT, i.e. does not have a single outermost SELECT
  • if it does not have exactly 1 table in its FROM list; 0 tables would occur if we ever support a SELECT without a FROM e.g., for generating a row without an underlying table (like what we do for an INSERT of a VALUES list); >1 tables occurs when joins are in the tree.
  • if the table in its FROM list is not a base table (REMIND when views/from subqueries are added, this should be relaxed to be that the table is not updatable)
  • if it has a GROUP BY or HAVING (NOTE I am assuming that if and aggregate is detected in a SELECT w/o a GROUP BY, one has been added to show that the whole table is a group)
  • NOTE that cursors are updatable even if none of the columns in the select are updatable -- what they care about is the updatability of the columns of the target table.

Returns:

the known update mode for the cursor.

Throws:

StandardException - Thrown on error

optimizeStatement

public void optimizeStatement()
                       throws StandardException

Optimize a DML statement (which is the only type of statement that should need optimizing, I think). This method over-rides the one in QueryTreeNode. This method takes a bound tree, and returns an optimized tree. It annotates the bound tree rather than creating an entirely new tree. Throws an exception if the tree is not bound, or if the binding is out of date.

Overrides:

optimizeStatement in class DMLStatementNode

Throws:

StandardException - Thrown on error

activationKind

int activationKind()

Returns the type of activation this class generates.

Overrides:

activationKind in class DMLStatementNode

Returns:

either (NEED_CURSOR_ACTIVATION

Throws:

StandardException - Thrown on error

generate

public void generate(ActivationClassBuilder acb,
                     MethodBuilder mb)
              throws StandardException

Do code generation for this CursorNode

Overrides:

generate in class QueryTreeNode

Parameters:

acb - The ActivationClassBuilder for the class being built

mb - The method the generated code is to go into

Throws:

StandardException - Thrown on error

getUpdateBaseTableName

public java.lang.String getUpdateBaseTableName()

getUpdateExposedTableName

public java.lang.String getUpdateExposedTableName()
                                           throws StandardException

Throws:

StandardException

getUpdateSchemaName

public java.lang.String getUpdateSchemaName()
                                     throws StandardException

Throws:

StandardException

getUpdateMode

public int getUpdateMode()

getUpdatableColumns

private java.lang.String[] getUpdatableColumns()

Return String[] of names from the FOR UPDATE OF List

Returns:

String[] of names from the FOR UPDATE OF list.

genTargetResultColList

private ResultColumnDescriptor[] genTargetResultColList()
                                                 throws StandardException

Positioned update needs to know what the target result set looks like. This is generated from the UpdateColumnList available for the cursor, to describe the rows coming from the target result set under the cursor. This result set contains a superset of the updatable columns; the caller must verify that only those listed in the FOR UPDATE clause are used.

Returns:

a result column list containing a description of the target table (this may contain non-updatable columns).

Throws:

StandardException - Thrown on error

needsSavepoint

public boolean needsSavepoint()

Returns whether or not this Statement requires a set/clear savepoint around its execution. The following statement "types" do not require them: Cursor - unnecessary and won't work in a read only environment Xact - savepoint will get blown away underneath us during commit/rollback

Overrides:

needsSavepoint in class StatementNode

Returns:

boolean Whether or not this Statement requires a set/clear savepoint

getCursorInfo

public java.lang.Object getCursorInfo()
                               throws StandardException

Get information about this cursor. For sps, this is info saved off of the original query tree (the one for the underlying query).

Overrides:

getCursorInfo in class QueryTreeNode

Returns:

the cursor info

Throws:

StandardException - thrown if generation fails

bindUpdateColumns

private void bindUpdateColumns(FromTable targetTable)
                        throws StandardException

Bind the update columns by their names to the target table of the cursor specification. Doesn't check for duplicates in the list, although it could... REVISIT: If the list is empty, should it expand it out? at present, it leaves it empty.

Parameters:

targetTable - The underlying target table

Throws:

StandardException - Thrown on error

getUpdateColumnNames

private java.lang.String[] getUpdateColumnNames()

Get an array of strings for each updatable column in this list.

Returns:

an array of strings

getXML

public java.lang.String getXML()

updateIndexStatisticsFor

public TableDescriptor[] updateIndexStatisticsFor()
                                           throws StandardException

Returns a list of base tables for which the index statistics of the associated indexes should be updated.

Overrides:

updateIndexStatisticsFor in class StatementNode

Returns:

A list of table descriptors (potentially empty).

Throws:

StandardException - if accessing the index descriptors of a base table fails

acceptChildren

void acceptChildren(Visitor v)
             throws StandardException

Accept the visitor for all visitable children of this node.

Overrides:

acceptChildren in class DMLStatementNode

Parameters:

v - the visitor

Throws:

StandardException - on error