gudusoft.gsqlparser.util

Class OraclePseudoColumnUtil

Object

gudusoft.gsqlparser.util.OraclePseudoColumnUtil

public final class OraclePseudoColumnUtil
extends Object

The single place that decides whether an Oracle identifier is a documented pseudocolumn rather than a reference to a column of a table.

Every caller that either publishes a classification (TCustomSqlStatement.linkColumnReferenceToTable) or answers a lookup (TObjectName.isValidColumnName, resolver2.ScopeBuilder) must go through this class. Keeping two hand-synchronised copies of the list is what let NEXTVAL and CURRVAL drift apart in Mantis #4675: the lookup path knew about NEXTVAL and the publish path did not, so the two answered differently for the same expression.

Why the list is split into groups instead of being flat

Oracle documents 18 pseudocolumns, but only some of those names are reserved words. A name that is not reserved is a perfectly legal column name, and several are common ones: OBJECT_ID is a real column of ALL_OBJECTS and DBA_OBJECTS. Classifying such a name as a pseudocolumn on sight would delete correct lineage for SELECT OBJECT_ID FROM ALL_OBJECTS while producing no error anywhere - exactly the silent false negative the project forbids.

So a name is only treated as a pseudocolumn when that is provable from the statement itself:

• isReservedPseudoColumn(java.lang.String) - the name is an Oracle reserved word, so an unquoted occurrence can never be a column. Always safe.
• isConnectByPseudoColumn(java.lang.String) - only meaningful under a CONNECT BY; the caller supplies that fact.
• isSequencePseudoColumn(java.lang.String) - only meaningful when qualified by something that is not a table or alias in scope.

Names that are neither reserved nor context-provable (ORA_ROWSCN, OBJECT_ID, OBJECT_VALUE, XMLDATA, COLUMN_VALUE) are deliberately absent. Without catalog metadata there is no way to tell them from a real column of the same name, and guessing in either direction is a defect.

See Also:

Oracle SQL Language Reference - Pseudocolumns

Method Summary

Modifier and Type	Method and Description
static boolean	isConnectByPseudoColumn(String nameOnly) True when nameOnly is a hierarchical-query pseudocolumn (CONNECT_BY_ISLEAF, CONNECT_BY_ISCYCLE).
static boolean	isDetachedReservedPseudoColumn(String nameOnly) True for a reserved-word pseudocolumn that belongs to the query rather than to a table (ROWNUM, LEVEL).
static boolean	isReservedPseudoColumn(String nameOnly) True when nameOnly is a pseudocolumn whose name is an Oracle reserved word, and therefore never a legal unquoted column name.
static boolean	isSequencePseudoColumn(String nameOnly) True when nameOnly is a sequence pseudocolumn (NEXTVAL, CURRVAL).
static boolean	isTableScopedPseudoColumn(String nameOnly) True for a reserved-word pseudocolumn that belongs to one specific table (ROWID).
static boolean	isVersionsPseudoColumn(String nameOnly) True when nameOnly is a flashback version query pseudocolumn (VERSIONS_STARTSCN and friends).

Methods inherited from class Object

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

Method Detail

isReservedPseudoColumn

public static boolean isReservedPseudoColumn(String nameOnly)

True when nameOnly is a pseudocolumn whose name is an Oracle reserved word, and therefore never a legal unquoted column name.

The caller is responsible for checking that the identifier was not quoted: "ROWID" is a distinct, legal, case-sensitive column name.

Parameters:

nameOnly - the single unqualified name segment, without quotes

Returns:

true if this is always a pseudocolumn

isDetachedReservedPseudoColumn

public static boolean isDetachedReservedPseudoColumn(String nameOnly)

True for a reserved-word pseudocolumn that belongs to the query rather than to a table (ROWNUM, LEVEL). These carry no table attribution at all.

Parameters:

nameOnly - the single unqualified name segment, without quotes

Returns:

true if this pseudocolumn has no owning table

isTableScopedPseudoColumn

public static boolean isTableScopedPseudoColumn(String nameOnly)

True for a reserved-word pseudocolumn that belongs to one specific table (ROWID).

These keep getSourceTable() and their entry in the table's linked columns - a ROWID really did come from that table, and dropping the attribution would lose information lineage consumers use. What changes is the reported EDbObjectType: notAColumn rather than column, so nothing tries to resolve the name against a catalog that will never contain it.

Parameters:

nameOnly - the single unqualified name segment, without quotes

Returns:

true if this pseudocolumn is scoped to a single table

isConnectByPseudoColumn

public static boolean isConnectByPseudoColumn(String nameOnly)

True when nameOnly is a hierarchical-query pseudocolumn (CONNECT_BY_ISLEAF, CONNECT_BY_ISCYCLE).

Callers must additionally establish that the enclosing query has a CONNECT BY clause; without one the same name is an ordinary identifier and may well be a real column.

Parameters:

nameOnly - the single unqualified name segment, without quotes

Returns:

true if this is a CONNECT BY pseudocolumn name

isSequencePseudoColumn

public static boolean isSequencePseudoColumn(String nameOnly)

True when nameOnly is a sequence pseudocolumn (NEXTVAL, CURRVAL).

Callers must additionally establish that the qualifier is a sequence rather than a table or alias in scope; x.CURRVAL where x is a table alias is a reference to a column named CURRVAL.

Parameters:

nameOnly - the single unqualified name segment, without quotes

Returns:

true if this is a sequence pseudocolumn name

isVersionsPseudoColumn

public static boolean isVersionsPseudoColumn(String nameOnly)

True when nameOnly is a flashback version query pseudocolumn (VERSIONS_STARTSCN and friends).

Callers must additionally establish that the FROM clause carries a VERSIONS BETWEEN clause.

Parameters:

nameOnly - the single unqualified name segment, without quotes

Returns:

true if this is a version query pseudocolumn name