org.tmatesoft.sqljet.core.internal

Interface ISqlJetBtree

All Known Implementing Classes:

SqlJetBtree

public interface ISqlJetBtree

A Btree handle A database connection contains a pointer to an instance of this object for every database file that it has open. This structure is opaque to the database connection. The database connection cannot see the internals of this structure and only deals with pointers to this structure. For some database files, the same underlying database cache might be shared between multiple connections. In that case, each contection has it own pointer to this object. But each instance of this object points to the same BtShared object. The database cache and the schema associated with the database file are all contained within the BtShared object.

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	SQLITE_FILE_HEADER
static SqlJetAutoVacuumMode	SQLJET_DEFAULT_AUTOVACUUM
static ISqlJetMemoryPointer	zMagicHeader

Method Summary

Methods

Modifier and Type	Method and Description
void	beginStmt() Start a statement subtransaction.
void	beginTrans(SqlJetTransactionMode mode) Attempt to start a new transaction.
void	clearTable(int table, int[] nChange) Delete all information from a single table in the database.
void	close() Close an open database and invalidate all cursors.
void	closeAllCursors()
void	commit() Do both phases of a commit.
void	commitPhaseOne(java.lang.String master) This routine does the first phase of a two-phase commit.
void	commitPhaseTwo() Commit the transaction currently in progress.
void	commitStmt() Commit the statment subtransaction currently in progress.
void	copyFile(ISqlJetBtree from) Copy the complete content of from.
int	createTable(java.util.Set<SqlJetBtreeTableCreateFlags> flags) Create a new BTree table.
int	dropTable(int table) Erase all information in a table and add the root of the table to the freelist.
void	enter() Enter a mutex on the given BTree object.
SqlJetAutoVacuumMode	getAutoVacuum() Return the value of the 'auto-vacuum' property.
int	getCacheSize()
ISqlJetBtreeCursor	getCursor(int table, boolean wrFlag, ISqlJetKeyInfo keyInfo) Create a new cursor for the BTree whose root is on the page iTable.
ISqlJetDbHandle	getDb()
java.io.File	getDirname() Return the pathname of the directory that contains the database file.
java.io.File	getFilename() Return the full pathname of the underlying database file.
SqlJetPagerJournalMode	getJournalMode()
java.io.File	getJournalname() Return the pathname of the journal file for this database.
int	getMeta(int idx) Read the meta-information out of a database file.
ISqlJetPager	getPager() Return the pager associated with a BTree.
int	getPageSize() Return the currently defined page size
int	getReserve()
SqlJetSafetyLevel	getSafetyLevel()
SqlJetSchema	getSchema() This function returns a pointer to a blob of memory associated with a single shared-btree.
SqlJetTransactionMode	getTransMode() Get transaction mode
void	incrVacuum() A write-transaction must be opened before calling this function.
java.lang.String	integrityCheck(int[] aRoot, int nRoot, int mxErr, int[] nErr) This routine does a complete check of the given BTree file.
boolean	isInReadTrans() Return true if a read (or write) transaction is active.
boolean	isInStmt() Return true if a statement transaction is active.
boolean	isInTrans() Return true if a transaction is active.
boolean	isSchemaLocked() Return true if another user of the same shared btree as the argument handle holds an exclusive lock on the sqlite_master table.
boolean	isSyncDisabled() Return TRUE if the given btree is set to safety level 1.
void	leave() Exit the recursive mutex on a Btree.
void	lockTable(int table, boolean isWriteLock) Obtain a lock on the table whose root page is iTab.
void	open(java.io.File filename, ISqlJetDbHandle db, java.util.Set<SqlJetBtreeFlags> flags, SqlJetFileType type, java.util.Set<SqlJetFileOpenPermission> permissions) Open a database file.
void	rollback() Rollback the transaction in progress.
void	rollbackStmt() Rollback the active statement subtransaction.
void	savepoint(SqlJetSavepointOperation op, int savepoint) The second argument to this function, op, is always SAVEPOINT_ROLLBACK or SAVEPOINT_RELEASE.
void	setAutoVacuum(SqlJetAutoVacuumMode autoVacuum) Change the 'auto-vacuum' property of the database.
void	setCacheSize(int mxPage) Change the limit on the number of pages allowed in the cache.
void	setJournalMode(SqlJetPagerJournalMode mode)
void	setMaxPageCount(int mxPage) Set the maximum page count for a database if mxPage is positive.
void	setPageSize(int pageSize, int nReserve) Change the default pages size and the number of reserved bytes per page.
void	setSafetyLevel(SqlJetSafetyLevel level) Change the way data is synced to disk in order to increase or decrease how well the database resists damage due to OS crashes and power failures.
void	setSchema(SqlJetSchema schema)
void	tripAllCursors(SqlJetErrorCode errCode) This routine sets the state to CURSOR_FAULT and the error code to errCode for every cursor on BtShared that pBtree references.
void	updateMeta(int idx, int value) Write meta-information back into the database.

Field Detail

SQLJET_DEFAULT_AUTOVACUUM

static final SqlJetAutoVacuumMode SQLJET_DEFAULT_AUTOVACUUM

SQLITE_FILE_HEADER

static final java.lang.String SQLITE_FILE_HEADER

See Also:

Constant Field Values

zMagicHeader

static final ISqlJetMemoryPointer zMagicHeader

Method Detail

open

void open(java.io.File filename,
        ISqlJetDbHandle db,
        java.util.Set<SqlJetBtreeFlags> flags,
        SqlJetFileType type,
        java.util.Set<SqlJetFileOpenPermission> permissions)
          throws SqlJetException

Open a database file. zFilename is the name of the database file. If zFilename is NULL a new database with a random name is created. This randomly named database file will be deleted when sqlite3BtreeClose() is called. If zFilename is ":memory:" then an in-memory database is created that is automatically destroyed when it is closed.

Parameters:

filename - Name of database file to open

db - Associated database connection

flags - Flags

fsFlags - Flags passed through to VFS open

Throws:

SqlJetException

close

void close()
           throws SqlJetException

Close an open database and invalidate all cursors.

Throws:

SqlJetException

setCacheSize

void setCacheSize(int mxPage)

Change the limit on the number of pages allowed in the cache. The maximum number of cache pages is set to the absolute value of mxPage. If mxPage is negative, the pager will operate asynchronously - it will not stop to do fsync()s to insure data is written to the disk surface before continuing. Transactions still work if synchronous is off, and the database cannot be corrupted if this program crashes. But if the operating system crashes or there is an abrupt power failure when synchronous is off, the database could be left in an inconsistent and unrecoverable state. Synchronous is on by default so database corruption is not normally a worry.

Parameters:

mxPage -

setSafetyLevel

void setSafetyLevel(SqlJetSafetyLevel level)

Change the way data is synced to disk in order to increase or decrease how well the database resists damage due to OS crashes and power failures. Level 1 is the same as asynchronous (no syncs() occur and there is a high probability of damage) Level 2 is the default. There is a very low but non-zero probability of damage. Level 3 reduces the probability of damage to near zero but with a write performance reduction.

Parameters:

level -

Throws:

SqlJetException

getSafetyLevel

SqlJetSafetyLevel getSafetyLevel()

setJournalMode

void setJournalMode(SqlJetPagerJournalMode mode)

getJournalMode

SqlJetPagerJournalMode getJournalMode()

isSyncDisabled

boolean isSyncDisabled()

Return TRUE if the given btree is set to safety level 1. In other words, return TRUE if no sync() occurs on the disk files.

Returns:

setPageSize

void setPageSize(int pageSize,
               int nReserve)
                 throws SqlJetException

Change the default pages size and the number of reserved bytes per page. The page size must be a power of 2 between 512 and 65536. If the page size supplied does not meet this constraint then the page size is not changed. Page sizes are constrained to be a power of two so that the region of the database file used for locking (beginning at PENDING_BYTE, the first byte past the 1GB boundary, 0x40000000) needs to occur at the beginning of a page. If parameter nReserve is less than zero, then the number of reserved bytes per page is left unchanged.

Parameters:

pageSize -

nReserve -

Throws:

SqlJetException

getPageSize

int getPageSize()

Return the currently defined page size

Returns:

setMaxPageCount

void setMaxPageCount(int mxPage)
                     throws SqlJetException

Set the maximum page count for a database if mxPage is positive. No changes are made if mxPage is 0 or negative. Regardless of the value of mxPage, return the maximum page count.

Parameters:

mxPage -

Throws:

SqlJetException

getReserve

int getReserve()

setAutoVacuum

void setAutoVacuum(SqlJetAutoVacuumMode autoVacuum)
                   throws SqlJetException

Change the 'auto-vacuum' property of the database. If the 'autoVacuum' parameter is non-zero, then auto-vacuum mode is enabled. If zero, it is disabled. The default value for the auto-vacuum property is determined by the SQLITE_DEFAULT_AUTOVACUUM macro.

Parameters:

autoVacuum -

Throws:

SqlJetException

getAutoVacuum

SqlJetAutoVacuumMode getAutoVacuum()

Return the value of the 'auto-vacuum' property. If auto-vacuum is enabled 1 is returned. Otherwise 0.

Returns:

Throws:

SqlJetException

getTransMode

SqlJetTransactionMode getTransMode()

Get transaction mode

Returns:

beginTrans

void beginTrans(SqlJetTransactionMode mode)
                throws SqlJetException

Attempt to start a new transaction. A write-transaction is started if the second argument is nonzero, otherwise a read- transaction. If the second argument is 2 or more and exclusive transaction is started, meaning that no other process is allowed to access the database. A preexisting transaction may not be upgraded to exclusive by calling this routine a second time - the exclusivity flag only works for a new transaction. A write-transaction must be started before attempting any changes to the database. None of the following routines will work unless a transaction is started first: createTable() createIndex() clearTable() dropTable() insert() delete() updateMeta() If an initial attempt to acquire the lock fails because of lock contention and the database was previously unlocked, then invoke the busy handler if there is one. But if there was previously a read-lock, do not invoke the busy handler - just return BUSY. BUSY is returned when there is already a read-lock in order to avoid a deadlock. Suppose there are two processes A and B. A has a read lock and B has a reserved lock. B tries to promote to exclusive but is blocked because of A's read lock. A tries to promote to reserved but is blocked by B. One or the other of the two processes must give way or there can be no progress. By returning BUSY and not invoking the busy callback when A already has a read lock, we encourage A to give up and let B proceed.

Parameters:

mode -

Throws:

SqlJetException

commitPhaseOne

void commitPhaseOne(java.lang.String master)
                    throws SqlJetException

This routine does the first phase of a two-phase commit. This routine causes a rollback journal to be created (if it does not already exist) and populated with enough information so that if a power loss occurs the database can be restored to its original state by playing back the journal. Then the contents of the journal are flushed out to the disk. After the journal is safely on oxide, the changes to the database are written into the database file and flushed to oxide. At the end of this call, the rollback journal still exists on the disk and we are still holding all locks, so the transaction has not committed. See sqlite3BtreeCommit() for the second phase of the commit process. This call is a no-op if no write-transaction is currently active on pBt. Otherwise, sync the database file for the btree pBt. zMaster points to the name of a master journal file that should be written into the individual journal file, or is NULL, indicating no master journal file (single database transaction). When this is called, the master journal should already have been created, populated with this journal pointer and synced to disk. Once this is routine has returned, the only thing required to commit the write-transaction for this database file is to delete the journal.

Parameters:

master -

Throws:

SqlJetException

commitPhaseTwo

void commitPhaseTwo()
                    throws SqlJetException

Commit the transaction currently in progress. This routine implements the second phase of a 2-phase commit. The sqlite3BtreeSync() routine does the first phase and should be invoked prior to calling this routine. The sqlite3BtreeSync() routine did all the work of writing information out to disk and flushing the contents so that they are written onto the disk platter. All this routine has to do is delete or truncate the rollback journal (which causes the transaction to commit) and drop locks. This will release the write lock on the database file. If there are no active cursors, it also releases the read lock.

Throws:

SqlJetException

commit

void commit()
            throws SqlJetException

Do both phases of a commit.

Throws:

SqlJetException

rollback

void rollback()
              throws SqlJetException

Rollback the transaction in progress. All cursors will be invalided by this operation. Any attempt to use a cursor that was open at the beginning of this operation will result in an error. This will release the write lock on the database file. If there are no active cursors, it also releases the read lock.

Throws:

SqlJetException

beginStmt

void beginStmt()
               throws SqlJetException

Start a statement subtransaction. The subtransaction can can be rolled back independently of the main transaction. You must start a transaction before starting a subtransaction. The subtransaction is ended automatically if the main transaction commits or rolls back. Only one subtransaction may be active at a time. It is an error to try to start a new subtransaction if another subtransaction is already active. Statement subtransactions are used around individual SQL statements that are contained within a BEGIN...COMMIT block. If a constraint error occurs within the statement, the effect of that one statement can be rolled back without having to rollback the entire transaction.

Throws:

SqlJetException

commitStmt

void commitStmt()
                throws SqlJetException

Commit the statment subtransaction currently in progress. If no subtransaction is active, this is a no-op.

Throws:

SqlJetException

rollbackStmt

void rollbackStmt()
                  throws SqlJetException

Rollback the active statement subtransaction. If no subtransaction is active this routine is a no-op. All cursors will be invalidated by this operation. Any attempt to use a cursor that was open at the beginning of this operation will result in an error.

Throws:

SqlJetException

createTable

int createTable(java.util.Set<SqlJetBtreeTableCreateFlags> flags)
                throws SqlJetException

Create a new BTree table. Returns the page number for the root page of the new table. The type of type is determined by the flags parameter. Only the following values of flags are currently in use. Other values for flags might not work: INTKEY|LEAFDATA Used for SQL tables with rowid keys ZERODATA Used for SQL indices

Parameters:

flags -

Returns:

the page number for the root page of the new table

Throws:

SqlJetException

isInTrans

boolean isInTrans()

Return true if a transaction is active.

Returns:

isInStmt

boolean isInStmt()

Return true if a statement transaction is active.

Returns:

isInReadTrans

boolean isInReadTrans()

Return true if a read (or write) transaction is active.

Returns:

getSchema

SqlJetSchema getSchema()

This function returns a pointer to a blob of memory associated with a single shared-btree. The memory is used by client code for its own purposes (for example, to store a high-level schema associated with the shared-btree).

Returns:

setSchema

void setSchema(SqlJetSchema schema)

Parameters:

schema -

isSchemaLocked

boolean isSchemaLocked()

Return true if another user of the same shared btree as the argument handle holds an exclusive lock on the sqlite_master table.

Returns:

Throws:

SqlJetException

lockTable

void lockTable(int table,
             boolean isWriteLock)

Obtain a lock on the table whose root page is iTab. The lock is a write lock if isWritelock is true or a read lock if it is false.

Parameters:

iTab -

isWriteLock -

Throws:

SqlJetException

savepoint

void savepoint(SqlJetSavepointOperation op,
             int savepoint)
               throws SqlJetException

The second argument to this function, op, is always SAVEPOINT_ROLLBACK or SAVEPOINT_RELEASE. This function either releases or rolls back the savepoint identified by parameter iSavepoint, depending on the value of op. Normally, iSavepoint is greater than or equal to zero. However, if op is SAVEPOINT_ROLLBACK, then iSavepoint may also be -1. In this case the contents of the entire transaction are rolled back. This is different from a normal transaction rollback, as no locks are released and the transaction remains open.

Parameters:

op -

iSavepoint -

Throws:

SqlJetException

getFilename

java.io.File getFilename()

Return the full pathname of the underlying database file. The pager filename is invariant as long as the pager is open so it is safe to access without the BtShared mutex.

Returns:

getDirname

java.io.File getDirname()

Return the pathname of the directory that contains the database file. The pager directory name is invariant as long as the pager is open so it is safe to access without the BtShared mutex.

Returns:

getJournalname

java.io.File getJournalname()

Return the pathname of the journal file for this database. The return value of this routine is the same regardless of whether the journal file has been created or not. The pager journal filename is invariant as long as the pager is open so it is safe to access without the BtShared mutex.

Returns:

copyFile

void copyFile(ISqlJetBtree from)
              throws SqlJetException

Copy the complete content of from. A transaction must be active for both files. The size of file may be reduced by this operation. If anything goes wrong, the transaction is rolled back. If successful, commitPhaseOne() may be called before returning. The caller should finish committing the transaction by calling commit().

Parameters:

from -

Throws:

SqlJetException

incrVacuum

void incrVacuum()
                throws SqlJetException

A write-transaction must be opened before calling this function. It performs a single unit of work towards an incremental vacuum. If the incremental vacuum is finished after this function has run, DONE is thrown. If it is not finished, but no error occured, none isn't thrown. Otherwise an SQLite error code.

Throws:

SqlJetException

dropTable

int dropTable(int table)
              throws SqlJetException

Erase all information in a table and add the root of the table to the freelist. Except, the root of the principle table (the one on page 1) is never added to the freelist. This routine will fail with LOCKED if there are any open cursors on the table. If AUTOVACUUM is enabled and the page at table is not the last root page in the database file, then the last root page in the database file is moved into the slot formerly occupied by table and that last slot formerly occupied by the last root page is added to the freelist instead of iTable. In this say, all root pages are kept at the beginning of the database file, which is necessary for AUTOVACUUM to work right. Returned is the page number that used to be the last root page in the file before the move. If no page gets moved, returned is 0. The last root page is recorded in meta[3] and the value of meta[3] is updated by this procedure.

Parameters:

table -

Returns:

Throws:

SqlJetException

clearTable

void clearTable(int table,
              int[] nChange)
                throws SqlJetException

Delete all information from a single table in the database. Table is the page number of the root of the table. After this routine returns, the root page is empty, but still exists. This routine will fail with LOCKED if there are any open read cursors on the table. Open write cursors are moved to the root of the table. If nChange is not NULL, then table table must be an intkey table. The integer value pointed to by nChange[0] is incremented by the number of entries in the table.

Parameters:

table -

Throws:

SqlJetException

getMeta

int getMeta(int idx)
            throws SqlJetException

Read the meta-information out of a database file. Meta[0] is the number of free pages currently in the database. Meta[1] through meta[15] are available for use by higher layers. Meta[0] is read-only, the others are read/write. The schema layer numbers meta values differently. At the schema layer (and the SetCookie and ReadCookie opcodes) the number of free pages is not visible. So Cookie[0] is the same as Meta[1].

Parameters:

idx -

Returns:

Throws:

SqlJetException

updateMeta

void updateMeta(int idx,
              int value)
                throws SqlJetException

Write meta-information back into the database. Meta[0] is read-only and may not be written.

Parameters:

idx -

value -

Throws:

SqlJetException

tripAllCursors

void tripAllCursors(SqlJetErrorCode errCode)
                    throws SqlJetException

This routine sets the state to CURSOR_FAULT and the error code to errCode for every cursor on BtShared that pBtree references. Every cursor is tripped, including cursors that belong to other database connections that happen to be sharing the cache with pBtree. This routine gets called when a rollback occurs. All cursors using the same cache must be tripped to prevent them from trying to use the btree after the rollback. The rollback may have deleted tables or moved root pages, so it is not sufficient to save the state of the cursor. The cursor must be invalidated.

Parameters:

errCode -

Throws:

SqlJetException

integrityCheck

java.lang.String integrityCheck(int[] aRoot,
                              int nRoot,
                              int mxErr,
                              int[] nErr)
                                throws SqlJetException

This routine does a complete check of the given BTree file. aRoot[] is an array of pages numbers were each page number is the root page of a table. nRoot is the number of entries in aRoot. Write the number of error seen in nErr[0]. Except for some memory allocation errors, an error message held in memory obtained from malloc is returned if nErr[0] is non-zero. If nErr[0]==0 then NULL is returned. If a memory allocation error occurs, NULL is returned.

Returns:

Throws:

SqlJetException

getPager

ISqlJetPager getPager()
                      throws SqlJetException

Return the pager associated with a BTree. This routine is used for testing and debugging only.

Returns:

Throws:

SqlJetException

getCursor

ISqlJetBtreeCursor getCursor(int table,
                           boolean wrFlag,
                           ISqlJetKeyInfo keyInfo)
                             throws SqlJetException

Create a new cursor for the BTree whose root is on the page iTable. The act of acquiring a cursor gets a read lock on the database file. If wrFlag==0, then the cursor can only be used for reading. If wrFlag==1, then the cursor can be used for reading or for writing if other conditions for writing are also met. These are the conditions that must be met in order for writing to be allowed: 1: The cursor must have been opened with wrFlag==1 2: Other database connections that share the same pager cache but which are not in the READ_UNCOMMITTED state may not have cursors open with wrFlag==0 on the same table. Otherwise the changes made by this write cursor would be visible to the read cursors in the other database connection. 3: The database must be writable (not on read-only media) 4: There must be an active transaction. No checking is done to make sure that page iTable really is the root page of a b-tree. If it is not, then the cursor acquired will not work correctly. It is assumed that the sqlite3BtreeCursorSize() bytes of memory pointed to by pCur have been zeroed by the caller.

Parameters:

table - Index of root page

wrFlag - true for writing. false for read-only

keyInfo - First argument to compare function

Returns:

Throws:

SqlJetException

enter

void enter()

Enter a mutex on the given BTree object. If the object is not sharable, then no mutex is ever required and this routine is a no-op. The underlying mutex is non-recursive. But we keep a reference count in Btree.wantToLock so the behavior of this interface is recursive. To avoid deadlocks, multiple Btrees are locked in the same order by all database connections. The p->pNext is a list of other Btrees belonging to the same database connection as the p Btree which need to be locked after p. If we cannot get a lock on p, then first unlock all of the others on p->pNext, then wait for the lock to become available on p, then relock all of the subsequent Btrees that desire a lock.

leave

void leave()

Exit the recursive mutex on a Btree.

getCacheSize

int getCacheSize()

Returns:

closeAllCursors

void closeAllCursors()
                     throws SqlJetException

Throws:

SqlJetException

getDb

ISqlJetDbHandle getDb()

Returns: