[sql] Import reference version of SQLite 3.17..

third_party/sqlite/sqlite-src-3170000/ext/rbu/sqlite3rbu.h

+/*
+** 2014 August 30
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains the public interface for the RBU extension. 
+*/
+
+/*
+** SUMMARY
+**
+** Writing a transaction containing a large number of operations on 
+** b-tree indexes that are collectively larger than the available cache
+** memory can be very inefficient. 
+**
+** The problem is that in order to update a b-tree, the leaf page (at least)
+** containing the entry being inserted or deleted must be modified. If the
+** working set of leaves is larger than the available cache memory, then a 
+** single leaf that is modified more than once as part of the transaction 
+** may be loaded from or written to the persistent media multiple times.
+** Additionally, because the index updates are likely to be applied in
+** random order, access to pages within the database is also likely to be in 
+** random order, which is itself quite inefficient.
+**
+** One way to improve the situation is to sort the operations on each index
+** by index key before applying them to the b-tree. This leads to an IO
+** pattern that resembles a single linear scan through the index b-tree,
+** and all but guarantees each modified leaf page is loaded and stored 
+** exactly once. SQLite uses this trick to improve the performance of
+** CREATE INDEX commands. This extension allows it to be used to improve
+** the performance of large transactions on existing databases.
+**
+** Additionally, this extension allows the work involved in writing the 
+** large transaction to be broken down into sub-transactions performed 
+** sequentially by separate processes. This is useful if the system cannot 
+** guarantee that a single update process will run for long enough to apply 
+** the entire update, for example because the update is being applied on a 
+** mobile device that is frequently rebooted. Even after the writer process 
+** has committed one or more sub-transactions, other database clients continue
+** to read from the original database snapshot. In other words, partially 
+** applied transactions are not visible to other clients. 
+**
+** "RBU" stands for "Resumable Bulk Update". As in a large database update
+** transmitted via a wireless network to a mobile device. A transaction
+** applied using this extension is hence refered to as an "RBU update".
+**
+**
+** LIMITATIONS
+**
+** An "RBU update" transaction is subject to the following limitations:
+**
+**   * The transaction must consist of INSERT, UPDATE and DELETE operations
+**     only.
+**
+**   * INSERT statements may not use any default values.
+**
+**   * UPDATE and DELETE statements must identify their target rows by 
+**     non-NULL PRIMARY KEY values. Rows with NULL values stored in PRIMARY
+**     KEY fields may not be updated or deleted. If the table being written 
+**     has no PRIMARY KEY, affected rows must be identified by rowid.
+**
+**   * UPDATE statements may not modify PRIMARY KEY columns.
+**
+**   * No triggers will be fired.
+**
+**   * No foreign key violations are detected or reported.
+**
+**   * CHECK constraints are not enforced.
+**
+**   * No constraint handling mode except for "OR ROLLBACK" is supported.
+**
+**
+** PREPARATION
+**
+** An "RBU update" is stored as a separate SQLite database. A database
+** containing an RBU update is an "RBU database". For each table in the 
+** target database to be updated, the RBU database should contain a table
+** named "data_<target name>" containing the same set of columns as the
+** target table, and one more - "rbu_control". The data_% table should 
+** have no PRIMARY KEY or UNIQUE constraints, but each column should have
+** the same type as the corresponding column in the target database.
+** The "rbu_control" column should have no type at all. For example, if
+** the target database contains:
+**
+**   CREATE TABLE t1(a INTEGER PRIMARY KEY, b TEXT, c UNIQUE);
+**
+** Then the RBU database should contain:
+**
+**   CREATE TABLE data_t1(a INTEGER, b TEXT, c, rbu_control);
+**
+** The order of the columns in the data_% table does not matter.
+**
+** Instead of a regular table, the RBU database may also contain virtual
+** tables or view named using the data_<target> naming scheme. 
+**
+** Instead of the plain data_<target> naming scheme, RBU database tables 
+** may also be named data<integer>_<target>, where <integer> is any sequence
+** of zero or more numeric characters (0-9). This can be significant because
+** tables within the RBU database are always processed in order sorted by 
+** name. By judicious selection of the <integer> portion of the names
+** of the RBU tables the user can therefore control the order in which they
+** are processed. This can be useful, for example, to ensure that "external
+** content" FTS4 tables are updated before their underlying content tables.
+**
+** If the target database table is a virtual table or a table that has no
+** PRIMARY KEY declaration, the data_% table must also contain a column 
+** named "rbu_rowid". This column is mapped to the tables implicit primary 
+** key column - "rowid". Virtual tables for which the "rowid" column does 
+** not function like a primary key value cannot be updated using RBU. For 
+** example, if the target db contains either of the following:
+**
+**   CREATE VIRTUAL TABLE x1 USING fts3(a, b);
+**   CREATE TABLE x1(a, b)
+**
+** then the RBU database should contain:
+**
+**   CREATE TABLE data_x1(a, b, rbu_rowid, rbu_control);
+**
+** All non-hidden columns (i.e. all columns matched by "SELECT *") of the
+** target table must be present in the input table. For virtual tables,
+** hidden columns are optional - they are updated by RBU if present in
+** the input table, or not otherwise. For example, to write to an fts4
+** table with a hidden languageid column such as:
+**
+**   CREATE VIRTUAL TABLE ft1 USING fts4(a, b, languageid='langid');
+**
+** Either of the following input table schemas may be used:
+**
+**   CREATE TABLE data_ft1(a, b, langid, rbu_rowid, rbu_control);
+**   CREATE TABLE data_ft1(a, b, rbu_rowid, rbu_control);
+**
+** For each row to INSERT into the target database as part of the RBU 
+** update, the corresponding data_% table should contain a single record
+** with the "rbu_control" column set to contain integer value 0. The
+** other columns should be set to the values that make up the new record 
+** to insert. 
+**
+** If the target database table has an INTEGER PRIMARY KEY, it is not 
+** possible to insert a NULL value into the IPK column. Attempting to 
+** do so results in an SQLITE_MISMATCH error.
+**
+** For each row to DELETE from the target database as part of the RBU 
+** update, the corresponding data_% table should contain a single record
+** with the "rbu_control" column set to contain integer value 1. The
+** real primary key values of the row to delete should be stored in the
+** corresponding columns of the data_% table. The values stored in the
+** other columns are not used.
+**
+** For each row to UPDATE from the target database as part of the RBU 
+** update, the corresponding data_% table should contain a single record
+** with the "rbu_control" column set to contain a value of type text.
+** The real primary key values identifying the row to update should be 
+** stored in the corresponding columns of the data_% table row, as should
+** the new values of all columns being update. The text value in the 
+** "rbu_control" column must contain the same number of characters as
+** there are columns in the target database table, and must consist entirely
+** of 'x' and '.' characters (or in some special cases 'd' - see below). For 
+** each column that is being updated, the corresponding character is set to
+** 'x'. For those that remain as they are, the corresponding character of the
+** rbu_control value should be set to '.'. For example, given the tables 
+** above, the update statement:
+**
+**   UPDATE t1 SET c = 'usa' WHERE a = 4;
+**
+** is represented by the data_t1 row created by:
+**
+**   INSERT INTO data_t1(a, b, c, rbu_control) VALUES(4, NULL, 'usa', '..x');
+**
+** Instead of an 'x' character, characters of the rbu_control value specified
+** for UPDATEs may also be set to 'd'. In this case, instead of updating the
+** target table with the value stored in the corresponding data_% column, the
+** user-defined SQL function "rbu_delta()" is invoked and the result stored in
+** the target table column. rbu_delta() is invoked with two arguments - the
+** original value currently stored in the target table column and the 
+** value specified in the data_xxx table.
+**
+** For example, this row:
+**
+**   INSERT INTO data_t1(a, b, c, rbu_control) VALUES(4, NULL, 'usa', '..d');
+**
+** is similar to an UPDATE statement such as: 
+**
+**   UPDATE t1 SET c = rbu_delta(c, 'usa') WHERE a = 4;
+**
+** Finally, if an 'f' character appears in place of a 'd' or 's' in an 
+** ota_control string, the contents of the data_xxx table column is assumed
+** to be a "fossil delta" - a patch to be applied to a blob value in the
+** format used by the fossil source-code management system. In this case
+** the existing value within the target database table must be of type BLOB. 
+** It is replaced by the result of applying the specified fossil delta to
+** itself.
+**
+** If the target database table is a virtual table or a table with no PRIMARY
+** KEY, the rbu_control value should not include a character corresponding 
+** to the rbu_rowid value. For example, this:
+**
+**   INSERT INTO data_ft1(a, b, rbu_rowid, rbu_control) 
+**       VALUES(NULL, 'usa', 12, '.x');
+**
+** causes a result similar to:
+**
+**   UPDATE ft1 SET b = 'usa' WHERE rowid = 12;
+**
+** The data_xxx tables themselves should have no PRIMARY KEY declarations.
+** However, RBU is more efficient if reading the rows in from each data_xxx
+** table in "rowid" order is roughly the same as reading them sorted by
+** the PRIMARY KEY of the corresponding target database table. In other 
+** words, rows should be sorted using the destination table PRIMARY KEY 
+** fields before they are inserted into the data_xxx tables.
+**
+** USAGE
+**
+** The API declared below allows an application to apply an RBU update 
+** stored on disk to an existing target database. Essentially, the 
+** application:
+**
+**     1) Opens an RBU handle using the sqlite3rbu_open() function.
+**
+**     2) Registers any required virtual table modules with the database
+**        handle returned by sqlite3rbu_db(). Also, if required, register
+**        the rbu_delta() implementation.
+**
+**     3) Calls the sqlite3rbu_step() function one or more times on
+**        the new handle. Each call to sqlite3rbu_step() performs a single
+**        b-tree operation, so thousands of calls may be required to apply 
+**        a complete update.
+**
+**     4) Calls sqlite3rbu_close() to close the RBU update handle. If
+**        sqlite3rbu_step() has been called enough times to completely
+**        apply the update to the target database, then the RBU database
+**        is marked as fully applied. Otherwise, the state of the RBU 
+**        update application is saved in the RBU database for later 
+**        resumption.
+**
+** See comments below for more detail on APIs.
+**
+** If an update is only partially applied to the target database by the
+** time sqlite3rbu_close() is called, various state information is saved 
+** within the RBU database. This allows subsequent processes to automatically
+** resume the RBU update from where it left off.
+**
+** To remove all RBU extension state information, returning an RBU database 
+** to its original contents, it is sufficient to drop all tables that begin
+** with the prefix "rbu_"
+**
+** DATABASE LOCKING
+**
+** An RBU update may not be applied to a database in WAL mode. Attempting
+** to do so is an error (SQLITE_ERROR).
+**
+** While an RBU handle is open, a SHARED lock may be held on the target
+** database file. This means it is possible for other clients to read the
+** database, but not to write it.
+**
+** If an RBU update is started and then suspended before it is completed,
+** then an external client writes to the database, then attempting to resume
+** the suspended RBU update is also an error (SQLITE_BUSY).
+*/
+
+#ifndef _SQLITE3RBU_H
+#define _SQLITE3RBU_H
+
+#include "sqlite3.h"              /* Required for error code definitions */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct sqlite3rbu sqlite3rbu;
+
+/*
+** Open an RBU handle.
+**
+** Argument zTarget is the path to the target database. Argument zRbu is
+** the path to the RBU database. Each call to this function must be matched
+** by a call to sqlite3rbu_close(). When opening the databases, RBU passes
+** the SQLITE_CONFIG_URI flag to sqlite3_open_v2(). So if either zTarget
+** or zRbu begin with "file:", it will be interpreted as an SQLite 
+** database URI, not a regular file name.
+**
+** If the zState argument is passed a NULL value, the RBU extension stores 
+** the current state of the update (how many rows have been updated, which 
+** indexes are yet to be updated etc.) within the RBU database itself. This
+** can be convenient, as it means that the RBU application does not need to
+** organize removing a separate state file after the update is concluded. 
+** Or, if zState is non-NULL, it must be a path to a database file in which 
+** the RBU extension can store the state of the update.
+**
+** When resuming an RBU update, the zState argument must be passed the same
+** value as when the RBU update was started.
+**
+** Once the RBU update is finished, the RBU extension does not 
+** automatically remove any zState database file, even if it created it.
+**
+** By default, RBU uses the default VFS to access the files on disk. To
+** use a VFS other than the default, an SQLite "file:" URI containing a
+** "vfs=..." option may be passed as the zTarget option.
+**
+** IMPORTANT NOTE FOR ZIPVFS USERS: The RBU extension works with all of
+** SQLite's built-in VFSs, including the multiplexor VFS. However it does
+** not work out of the box with zipvfs. Refer to the comment describing
+** the zipvfs_create_vfs() API below for details on using RBU with zipvfs.
+*/
+sqlite3rbu *sqlite3rbu_open(
+  const char *zTarget, 
+  const char *zRbu,
+  const char *zState
+);
+
+/*
+** Open an RBU handle to perform an RBU vacuum on database file zTarget.
+** An RBU vacuum is similar to SQLite's built-in VACUUM command, except
+** that it can be suspended and resumed like an RBU update.
+**
+** The second argument to this function identifies a database in which 
+** to store the state of the RBU vacuum operation if it is suspended. The 
+** first time sqlite3rbu_vacuum() is called, to start an RBU vacuum
+** operation, the state database should either not exist or be empty
+** (contain no tables). If an RBU vacuum is suspended by calling 
+** sqlite3rbu_close() on the RBU handle before sqlite3rbu_step() has
+** returned SQLITE_DONE, the vacuum state is stored in the state database. 
+** The vacuum can be resumed by calling this function to open a new RBU
+** handle specifying the same target and state databases.
+**
+** If the second argument passed to this function is NULL, then the
+** name of the state database is "<database>-vacuum", where <database>
+** is the name of the target database file. In this case, on UNIX, if the
+** state database is not already present in the file-system, it is created
+** with the same permissions as the target db is made.
+**
+** This function does not delete the state database after an RBU vacuum
+** is completed, even if it created it. However, if the call to
+** sqlite3rbu_close() returns any value other than SQLITE_OK, the contents
+** of the state tables within the state database are zeroed. This way,
+** the next call to sqlite3rbu_vacuum() opens a handle that starts a 
+** new RBU vacuum operation.
+**
+** As with sqlite3rbu_open(), Zipvfs users should rever to the comment
+** describing the sqlite3rbu_create_vfs() API function below for 
+** a description of the complications associated with using RBU with 
+** zipvfs databases.
+*/
+sqlite3rbu *sqlite3rbu_vacuum(
+  const char *zTarget, 
+  const char *zState
+);
+
+/*
+** Internally, each RBU connection uses a separate SQLite database 
+** connection to access the target and rbu update databases. This
+** API allows the application direct access to these database handles.
+**
+** The first argument passed to this function must be a valid, open, RBU
+** handle. The second argument should be passed zero to access the target
+** database handle, or non-zero to access the rbu update database handle.
+** Accessing the underlying database handles may be useful in the
+** following scenarios:
+**
+**   * If any target tables are virtual tables, it may be necessary to
+**     call sqlite3_create_module() on the target database handle to 
+**     register the required virtual table implementations.
+**
+**   * If the data_xxx tables in the RBU source database are virtual 
+**     tables, the application may need to call sqlite3_create_module() on
+**     the rbu update db handle to any required virtual table
+**     implementations.
+**
+**   * If the application uses the "rbu_delta()" feature described above,
+**     it must use sqlite3_create_function() or similar to register the
+**     rbu_delta() implementation with the target database handle.
+**
+** If an error has occurred, either while opening or stepping the RBU object,
+** this function may return NULL. The error code and message may be collected
+** when sqlite3rbu_close() is called.
+**
+** Database handles returned by this function remain valid until the next
+** call to any sqlite3rbu_xxx() function other than sqlite3rbu_db().
+*/
+sqlite3 *sqlite3rbu_db(sqlite3rbu*, int bRbu);
+
+/*
+** Do some work towards applying the RBU update to the target db. 
+**
+** Return SQLITE_DONE if the update has been completely applied, or 
+** SQLITE_OK if no error occurs but there remains work to do to apply
+** the RBU update. If an error does occur, some other error code is 
+** returned. 
+**
+** Once a call to sqlite3rbu_step() has returned a value other than
+** SQLITE_OK, all subsequent calls on the same RBU handle are no-ops
+** that immediately return the same value.
+*/
+int sqlite3rbu_step(sqlite3rbu *pRbu);
+
+/*
+** Force RBU to save its state to disk.
+**
+** If a power failure or application crash occurs during an update, following
+** system recovery RBU may resume the update from the point at which the state
+** was last saved. In other words, from the most recent successful call to 
+** sqlite3rbu_close() or this function.
+**
+** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
+*/
+int sqlite3rbu_savestate(sqlite3rbu *pRbu);
+
+/*
+** Close an RBU handle. 
+**
+** If the RBU update has been completely applied, mark the RBU database
+** as fully applied. Otherwise, assuming no error has occurred, save the
+** current state of the RBU update appliation to the RBU database.
+**
+** If an error has already occurred as part of an sqlite3rbu_step()
+** or sqlite3rbu_open() call, or if one occurs within this function, an
+** SQLite error code is returned. Additionally, *pzErrmsg may be set to
+** point to a buffer containing a utf-8 formatted English language error
+** message. It is the responsibility of the caller to eventually free any 
+** such buffer using sqlite3_free().
+**
+** Otherwise, if no error occurs, this function returns SQLITE_OK if the
+** update has been partially applied, or SQLITE_DONE if it has been 
+** completely applied.
+*/
+int sqlite3rbu_close(sqlite3rbu *pRbu, char **pzErrmsg);
+
+/*
+** Return the total number of key-value operations (inserts, deletes or 
+** updates) that have been performed on the target database since the
+** current RBU update was started.
+*/
+sqlite3_int64 sqlite3rbu_progress(sqlite3rbu *pRbu);
+
+/*
+** Obtain permyriadage (permyriadage is to 10000 as percentage is to 100) 
+** progress indications for the two stages of an RBU update. This API may
+** be useful for driving GUI progress indicators and similar.
+**
+** An RBU update is divided into two stages:
+**
+**   * Stage 1, in which changes are accumulated in an oal/wal file, and
+**   * Stage 2, in which the contents of the wal file are copied into the
+**     main database.
+**
+** The update is visible to non-RBU clients during stage 2. During stage 1
+** non-RBU reader clients may see the original database.
+**
+** If this API is called during stage 2 of the update, output variable 
+** (*pnOne) is set to 10000 to indicate that stage 1 has finished and (*pnTwo)
+** to a value between 0 and 10000 to indicate the permyriadage progress of
+** stage 2. A value of 5000 indicates that stage 2 is half finished, 
+** 9000 indicates that it is 90% finished, and so on.
+**
+** If this API is called during stage 1 of the update, output variable 
+** (*pnTwo) is set to 0 to indicate that stage 2 has not yet started. The
+** value to which (*pnOne) is set depends on whether or not the RBU 
+** database contains an "rbu_count" table. The rbu_count table, if it 
+** exists, must contain the same columns as the following:
+**
+**   CREATE TABLE rbu_count(tbl TEXT PRIMARY KEY, cnt INTEGER) WITHOUT ROWID;
+**
+** There must be one row in the table for each source (data_xxx) table within
+** the RBU database. The 'tbl' column should contain the name of the source
+** table. The 'cnt' column should contain the number of rows within the
+** source table.
+**
+** If the rbu_count table is present and populated correctly and this
+** API is called during stage 1, the *pnOne output variable is set to the
+** permyriadage progress of the same stage. If the rbu_count table does
+** not exist, then (*pnOne) is set to -1 during stage 1. If the rbu_count
+** table exists but is not correctly populated, the value of the *pnOne
+** output variable during stage 1 is undefined.
+*/
+void sqlite3rbu_bp_progress(sqlite3rbu *pRbu, int *pnOne, int *pnTwo);
+
+/*
+** Obtain an indication as to the current stage of an RBU update or vacuum.
+** This function always returns one of the SQLITE_RBU_STATE_XXX constants
+** defined in this file. Return values should be interpreted as follows:
+**
+** SQLITE_RBU_STATE_OAL:
+**   RBU is currently building a *-oal file. The next call to sqlite3rbu_step()
+**   may either add further data to the *-oal file, or compute data that will
+**   be added by a subsequent call.
+**
+** SQLITE_RBU_STATE_MOVE:
+**   RBU has finished building the *-oal file. The next call to sqlite3rbu_step()
+**   will move the *-oal file to the equivalent *-wal path. If the current
+**   operation is an RBU update, then the updated version of the database
+**   file will become visible to ordinary SQLite clients following the next
+**   call to sqlite3rbu_step().
+**
+** SQLITE_RBU_STATE_CHECKPOINT:
+**   RBU is currently performing an incremental checkpoint. The next call to
+**   sqlite3rbu_step() will copy a page of data from the *-wal file into
+**   the target database file.
+**
+** SQLITE_RBU_STATE_DONE:
+**   The RBU operation has finished. Any subsequent calls to sqlite3rbu_step()
+**   will immediately return SQLITE_DONE.
+**
+** SQLITE_RBU_STATE_ERROR:
+**   An error has occurred. Any subsequent calls to sqlite3rbu_step() will
+**   immediately return the SQLite error code associated with the error.
+*/
+#define SQLITE_RBU_STATE_OAL        1
+#define SQLITE_RBU_STATE_MOVE       2
+#define SQLITE_RBU_STATE_CHECKPOINT 3
+#define SQLITE_RBU_STATE_DONE       4
+#define SQLITE_RBU_STATE_ERROR      5
+
+int sqlite3rbu_state(sqlite3rbu *pRbu);
+
+/*
+** Create an RBU VFS named zName that accesses the underlying file-system
+** via existing VFS zParent. Or, if the zParent parameter is passed NULL, 
+** then the new RBU VFS uses the default system VFS to access the file-system.
+** The new object is registered as a non-default VFS with SQLite before 
+** returning.
+**
+** Part of the RBU implementation uses a custom VFS object. Usually, this
+** object is created and deleted automatically by RBU. 
+**
+** The exception is for applications that also use zipvfs. In this case,
+** the custom VFS must be explicitly created by the user before the RBU
+** handle is opened. The RBU VFS should be installed so that the zipvfs
+** VFS uses the RBU VFS, which in turn uses any other VFS layers in use 
+** (for example multiplexor) to access the file-system. For example,
+** to assemble an RBU enabled VFS stack that uses both zipvfs and 
+** multiplexor (error checking omitted):
+**
+**     // Create a VFS named "multiplex" (not the default).
+**     sqlite3_multiplex_initialize(0, 0);
+**
+**     // Create an rbu VFS named "rbu" that uses multiplexor. If the
+**     // second argument were replaced with NULL, the "rbu" VFS would
+**     // access the file-system via the system default VFS, bypassing the
+**     // multiplexor.
+**     sqlite3rbu_create_vfs("rbu", "multiplex");
+**
+**     // Create a zipvfs VFS named "zipvfs" that uses rbu.
+**     zipvfs_create_vfs_v3("zipvfs", "rbu", 0, xCompressorAlgorithmDetector);
+**
+**     // Make zipvfs the default VFS.
+**     sqlite3_vfs_register(sqlite3_vfs_find("zipvfs"), 1);
+**
+** Because the default VFS created above includes a RBU functionality, it
+** may be used by RBU clients. Attempting to use RBU with a zipvfs VFS stack
+** that does not include the RBU layer results in an error.
+**
+** The overhead of adding the "rbu" VFS to the system is negligible for 
+** non-RBU users. There is no harm in an application accessing the 
+** file-system via "rbu" all the time, even if it only uses RBU functionality 
+** occasionally.
+*/
+int sqlite3rbu_create_vfs(const char *zName, const char *zParent);
+
+/*
+** Deregister and destroy an RBU vfs created by an earlier call to
+** sqlite3rbu_create_vfs().
+**
+** VFS objects are not reference counted. If a VFS object is destroyed
+** before all database handles that use it have been closed, the results
+** are undefined.
+*/
+void sqlite3rbu_destroy_vfs(const char *zName);
+
+#ifdef __cplusplus
+}  /* end of the 'extern "C"' block */
+#endif
+
+#endif /* _SQLITE3RBU_H */