RefTable.h

RefTable is used to make a view on another table. Usually it is a view on a subset of the table, either in vertical or horizontal direction. Thus a subset of rows and/or columns. It will be the result of a select, sort, project or iterate function.

It acts to the user as a normal table. All gets and puts are handled by RefColumn which directs them to the referenced column while (if needed) converting the given row number to the row number in the referenced table. For that purpose RefTable maintains a Vector of the row numbers in the referenced table.

The RefTable constructor acts in a way that it will always reference the original table. This means that if a select is done on a RefTable, the resulting RefTable will also reference the original PlainTable. This is done to avoid long chains of RefTables. However, if ever some other kind of table views are introduced (like a join or a concatenation of similar tables), this cannot be used anymore. Most software already anticipates on that. The only exception is the code anding, oring tables (refAnd, etc.).

To Do

Maybe not allocating the row number vector for a projection. This saves space and time, but each rownr conversion will take a bit more time because it has to test if there is a vector.
Maybe maintain a Vector telling on which columns the table is ordered. This may speed up selection, but it is hard to check if the order is changed by a put.
Allow to remove a row or column from the RefTable
Allow to rename a column in the RefTable
Maybe implement doSort one time for a more efficient sort. (now everything is handled by BaseTable).

Member Description

RefTable (BaseTable*, Bool rowOrder, uInt initialNrrow)

Create a reference table object referencing the given BaseTable object. If the BaseTable is actually another RefTable, it will reference its referenced table (thus the original table) and it will take its vector of row numbers and projected column names into account. Thus if a select is done on a projected table, the resulting RefTable will have the same projection.

Construct a RefTable with an empty row number vector. rowOrder=True indicates that the order of the rows will not be disturbed (as will be the case for a sort). A row number vector of the given size is initially allocated. Later this RefTable will be filled in by the select, etc..

RefTable (BaseTable*, const Vector<uInt>& rowNumbers)

A RefTable with the given row numbers is constructed.

RefTable (BaseTable*, const Vector<Bool>& rowMask)

Create a reference table object out of a mask. The row number vector will consist of the rows for which the mask has a True value. The length of the mask must be the number of rows in the BaseTable.

RefTable (BaseTable*, const Vector<String>& columnNames)

Create a reference table object via projection (i.e. column selection). The row number vector is a copy of the given table.

RefTable (AipsIO&, const String& name, uInt nrrow, int option, const TableLock& lockOptions)

Create a reference table out of a file (written by writeRefTable). The referenced table will also be created (if not stored in the cache).

virtual ~RefTable()

The destructor flushes (i.e. writes) the table if it is opened for output and not marked for delete.

static void getLayout (TableDesc& desc, AipsIO& ios)

Return the layout of a table (i.e. description and #rows). This function has the advantage that only the minimal amount of information required is read from the table, thus it is much faster than a normal table open.
The number of rows is returned. The description of the table is stored in desc (its contents will be overwritten).

virtual void reopenRW()

Try to reopen the table (the underlying one) for read/write access. An exception is thrown if the table is not writable. Nothing is done if the table is already open for read/write.

virtual Bool asBigEndian() const

Is the table stored in big or little endian format?

virtual Bool isMultiUsed (Bool checkSubTable) const

Is the table in use (i.e. open) in another process? It always returns False.

virtual const TableLock& lockOptions() const

Get the locking info.

virtual void mergeLock (const TableLock& lockOptions)

Merge the given lock info with the existing one.

virtual Bool hasLock (FileLocker::LockType) const

Has this process the read or write lock, thus can the table be read or written safely?

virtual Bool lock (FileLocker::LockType, uInt nattempts)

Try to lock the table for read or write access.

virtual void unlock()

Unlock the table. This will also synchronize the table data, thus force the data to be written to disk.

virtual void flush (Bool fsync, Bool recursive)

Flush the table, i.e. write it to disk. Nothing will be done if the table is not writable. A flush can be executed at any time. When a table is marked for delete, the destructor will remove files written by intermediate flushes. Note that if necessary the destructor will do an implicit flush, unless it is executed due to an exception.

virtual void resync()

Resync the Table object with the table file.

virtual uInt getModifyCounter() const

Get the modify counter.

virtual Bool isWritable() const

Test if the parent table is opened as writable.

void getRef (AipsIO&, int option, const TableLock& lockOptions)

Read a reference table from a file. The referenced table will also be created (if not stored in the cache).

virtual void deepCopy (const String& newName, const Record& dataManagerInfo, int tableOption, Bool, int endianFormat, Bool noRows) const

Copy the table and all its subtables. It copies the contents of each row to get a real copy.

virtual int tableType() const

It returns the type of the parent table.

virtual TableDesc actualTableDesc() const

Get the actual table description.

virtual Record dataManagerInfo() const

Get the data manager info.

virtual TableRecord& keywordSet()

Get readonly access to the table keyword set.

virtual TableRecord& rwKeywordSet()

Get read/write access to the table keyword set. This requires that the table is locked (or it gets locked when using AutoLocking mode).

virtual BaseColumn* getColumn (uInt columnIndex) const

Get a column object using its index.

virtual BaseColumn* getColumn (const String& columnName) const

Get a column object using its name.

virtual Bool canRemoveRow() const

Test if it is possible to remove a row from this table.

virtual void removeRow (uInt rownr)

Remove the given row.

virtual Bool canRemoveColumn (const Vector<String>& columnNames) const

Test if columns can be removed (yes).

virtual void removeColumn (const Vector<String>& columnNames)

Remove columns.

virtual Bool canRenameColumn (const String& columnName) const

Test if a column can be renamed (yes).

virtual void renameColumn (const String& newName, const String& oldName)

Rename a column.

virtual DataManager* findDataManager (const String& dataManagerName) const

Find the data manager with the given name.

virtual Vector<uInt> rowNumbers() const

Get a vector of row numbers.

virtual BaseTable* root()

Get parent of this table.

uInt rootRownr (uInt rownr) const

Get rownr in root table. This converts the given row number to the row number in the root table.

Vector<uInt> rootRownr (const Vector<uInt>& rownrs) const

Get vector of rownrs in root table. This converts the given row numbers to row numbers in the root table.

virtual Bool rowOrder() const

Tell if the table is in row order.

virtual Vector<uInt>* rowStorage()

Get row number vector. This is used by the BaseTable logic and sort routines.

void addRownr (uInt rownr)

Add a rownr to reference table.

void setNrrow (uInt nrrow)

Set the exact number of rows in the table. An exception is thrown if more than current nrrow.

virtual Bool adjustRownrs (uInt nrrow, Vector<uInt>& rownrs, Bool determineOrder) const

Adjust the row numbers to be the actual row numbers in the root table. This is, for instance, used when a RefTable is sorted. Optionally it also determines if the resulting rows are in row order.

void refAnd (uInt nr1, const uInt* rows1, uInt nr2, const uInt* rows2)

And, or, subtract or xor the row numbers of 2 tables.

void refOr (uInt nr1, const uInt* rows1, uInt nr2, const uInt* rows2)

void refSub (uInt nr1, const uInt* rows1, uInt nr2, const uInt* rows2)

void refXor (uInt nr1, const uInt* rows1, uInt nr2, const uInt* rows2)

void refNot (uInt nr1, const uInt* rows1, uInt nrmain)

static uInt* getStorage (Vector<uInt>& rownrs)

Get the internal pointer in a rowStorage vector. It checks whether no copy is made of the data.

RefTable (const RefTable&)

Copy constructor is forbidden, because copying a table requires some more knowledge (like table name of result). Declaring it private, makes it unusable.

RefTable& operator= (const RefTable&)

Assignment is forbidden, because copying a table requires some more knowledge (like table name of result). Declaring it private, makes it unusable.

static void makeDesc (TableDesc& desc, const TableDesc& rootDesc, SimpleOrderedMap<String,String>& nameMap, Vector<String>& names)

void setup (BaseTable* btp, const Vector<String>& columnNames)

Setup the main parts of the object.
First create the name map (mapping column name in RefTable to the column in the original table). If the BaseTable is a RefTable, use its name map. Otherwise create the initial name map from the table description. A rename might change the map.
Create the RefColumn objects.
Create the initial TableInfo as a copy of the original BaseTable.

void makeRefCol()

Create the RefColumn objects for all columns in the description.

void writeRefTable (Bool fsync)

Write a reference table.