LuaSQLite3

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NAME

LuaSQLite 3 - a Lua 5.1 to 5.3 wrapper for the SQLite3 library

OVERVIEW

LuaSQLite 3 is a thin wrapper around the public domain SQLite3 database engine.

There are two modules, identical except that one links SQLite3 dynamically, the other statically.

The module lsqlite3 links SQLite3 dynamically. To use this module you need the SQLite3 library (DLL or .so). You can get it from http://www.sqlite.org/

The module lsqlite3complete links SQLite3 statically. The SQLite3 amalgamation source code is included in the LuaSQLite 3 distribution. This can simplify deployment, but might result in more than one copy of the SQLite library if other parts of the code also include it. See http://www.sqlite.org/howtocorrupt.html for an explanation on why it would be a bad idea.

Both modules support the creation and manipulation of SQLite3 databases. After a sqlite3 = require('lsqlite3') (or sqlite3 = require('lsqlite3complete')) the exported functions are called with prefix sqlite3. However, most sqlite3 functions are called via an object-oriented interface to either database or SQL statement objects; see below for details.

This documentation does not attempt to describe how SQLite3 itself works, it just describes the Lua binding and the available functions. For more information about the SQL features supported by SQLite3 and details about the syntax of SQL statements and queries, please see the SQLite3 documentation http://www.sqlite.org/. Using some of the advanced features (how to use callbacks, for instance) will require some familiarity with the SQLite3 API.

DOWNLOAD

LuaSQLite 3 source code can be downloaded from its Fossil (http://lua.sqlite.org/) page.

For lsqlite3 (but not for lsqlite3complete) you will also need to build or obtain an SQLite3 loadable library (DLL or .so). See http://www.sqlite.org/ for obtaining SQLite3 source code or downloading a binary SQLite3 library.

INSTALLATION

Luarocks (http://luarocks.org/) is the preferred mechanism to build and install lsqlite3 or lsqlite3complete; for lsqlite3 it assumes an SQLite3 library is already installed. For lsqlite3complete no SQLite3 library is needed.

EXAMPLES

The distribution contains an examples directory. The unit tests also show some example use.

VERIFICATION TESTS

The distribution contains a tests directory with some units tests using an enhanced version of Michael Roth's lunit called lunitx. Some of the tests were also derived from Michael's lua-sqlite3 module, and more unit tests added by Doug Currie. Get lunitx using Luarocks.

The distribution also contains some functional tests by Tiago.

This version of lsqlite3 was tested with SQLite 3.11.0 and 3.15.1.

REFERENCE

SQLite3 functions

sqlite3.complete

        sqlite3.complete(sql)

Returns true if the string sql comprises one or more complete SQL statements and false otherwise.

sqlite3.open

        sqlite3.open(filename)

Opens (or creates if it does not exist) an SQLite database with name filename and returns its handle as userdata (the returned object should be used for all further method calls in connection with this specific database, see Database methods). Example:

        myDB=sqlite3.open('MyDatabase.sqlite3')  -- open
        -- do some database calls...
        myDB:close()  -- close

In case of an error, the function returns nil, an error code and an error message.

Since 0.9.4, there is a second optional flags argument to sqlite3.open. 

        sqlite3.open(filename, flags)

See sqlite3_open_v2 for an explanation of these flags and options.

Example: 

        local db = sqlite3.open('foo.db', sqlite3.OPEN_READWRITE + sqlite3.OPEN_CREATE + sqlite3.OPEN_SHAREDCACHE)
The default value for flags is sqlite3.OPEN_READWRITE + sqlite3.OPEN_CREATE.

sqlite3.open_memory

        sqlite3.open_memory()

Opens an SQLite database in memory and returns its handle as userdata. In case of an error, the function returns nil, an error code and an error message. (In-memory databases are volatile as they are never stored on disk.)

sqlite3.open_ptr

        sqlite3.open_ptr(db_ptr)

Opens the SQLite database corresponding to the light userdata db_ptr and returns its handle as userdata. Use db:get_ptr to get a db_ptr for an open database.

sqlite3.backup_init

        sqlite3.backup_init(target_db, target_name, source_db, source_name)

Starts an SQLite Online Backup from source_db to target_db and returns its handle as userdata. The source_db and target_db are open databases; they may be in-memory or file-based databases. The target_name and source_name are "main" for the main database, "temp" for the temporary database, or the name specified after the AS keyword in an ATTACH statement for an attached database.

The source and target databases must be different, or else the init call will fail with an error. A call to sqlite3.backup_init will fail, returning NULL, if there is already a read or read-write transaction open on the target database.

If an error occurs within sqlite3.backup_init, then NULL is returned, and an error code and error message are stored in target_db. The error code and message for the failed call can be retrieved using the db:errcode, or db:errmsg.

sqlite3.temp_directory

        sqlite3.temp_directory([temp])

Sets or queries the directory used by SQLite for temporary files. If string temp is a directory name or nil, the temporary directory is set accordingly and the old value is returned. If temp is missing, the function simply returns the current temporary directory.

sqlite3.version

        sqlite3.version()

Returns a string with SQLite version information, in the form 'x.y[.z[.p]]'.

sqlite3.lversion

        sqlite3.lversion()

Returns a string with lsqlite3 library version information, in the form 'x.y[.z]'.

Database methods

After opening a database with sqlite3.open() or sqlite3.open_memory() the returned database object should be used for all further method calls in connection with that database. An open database object supports the following methods.

db:busy_handler

        db:busy_handler([func[,udata]])

Sets or removes a busy handler for a database. func is either a Lua function that implements the busy handler or nil to remove a previously set handler. This function returns nothing.

The handler function is called with two parameters: udata and the number of (re-)tries for a pending transaction. It should return nil, false or 0 if the transaction is to be aborted. All other values will result in another attempt to perform the transaction. (See the SQLite documentation for important hints about writing busy handlers.)

db:busy_timeout

        db:busy_timeout(t)

Sets a busy handler that waits for t milliseconds if a transaction cannot proceed. Calling this function will remove any busy handler set by db:busy_handler(); calling it with an argument less than or equal to 0 will turn off all busy handlers.

db:changes

        db:changes()

This function returns the number of database rows that were changed (or inserted or deleted) by the most recent SQL statement. Only changes that are directly specified by INSERT, UPDATE, or DELETE statements are counted. Auxiliary changes caused by triggers are not counted. Use db:total_changes() to find the total number of changes.

db:close

        db:close()

Closes a database. All SQL statements prepared using db:prepare() should have been finalized before this function is called. The function returns sqlite3.OK on success or else a numerical error code (see the list of Numerical error and result codes).

db:close_vm

        db:close_vm(temponly)

Finalizes all statements that have not been explicitly finalized. If temponly is true, only internal, temporary statements are finalized. This function returns nothing.

db:get_ptr

        db:get_ptr()

Returns a lightuserdata corresponding to the open db. Use with sqlite3.open_ptr to pass a database connection between threads. (When using lsqlite3 in a multithreaded environment, each thread has a separate Lua environment; full userdata structures can't be passed from one thread to another, but this is possible with lightuserdata.)

db:commit_hook

        db:commit_hook(func,udata)

This function installs a commit_hook callback handler. func is a Lua function that is invoked by SQLite3 whenever a transaction is commited. This callback receives one argument: the udata argument used when the callback was installed. If func returns false or nil the COMMIT is allowed to prodeed, otherwise the COMMIT is converted to a ROLLBACK.

See: db:rollback_hook and db:update_hook

db:create_aggregate

        db:create_aggregate(name,nargs,step,final[,userdata])

This function creates an aggregate callback function. Aggregates perform an operation over all rows in a query. name is a string with the name of the aggregate function as given in an SQL statement; nargs is the number of arguments this call will provide. step is the actual Lua function that gets called once for every row; it should accept a function context (see Methods for callback contexts) plus the same number of parameters as given in nargs. final is a function that is called once after all rows have been processed; it receives one argument, the function context. If provided, userdata can be any Lua value and would be returned by the context:user_data() method.

The function context can be used inside the two callback functions to communicate with SQLite3. Here is a simple example:

        db:exec[=[
          CREATE TABLE numbers(num1,num2);
          INSERT INTO numbers VALUES(1,11);
          INSERT INTO numbers VALUES(2,22);
          INSERT INTO numbers VALUES(3,33);
        ]=]
        local num_sum=0
        local function oneRow(context,num)  -- add one column in all rows
          num_sum=num_sum+num
        end
        local function afterLast(context)   -- return sum after last row has been processed
          context:result_number(num_sum)
          num_sum=0
        end
        db:create_aggregate("do_the_sums",1,oneRow,afterLast)
        for sum in db:urows('SELECT do_the_sums(num1) FROM numbers') do print("Sum of col 1:",sum) end
        for sum in db:urows('SELECT do_the_sums(num2) FROM numbers') do print("Sum of col 2:",sum) end

This prints:

        Sum of col 1:   6
        Sum of col 2:   66

db:create_collation

        db:create_collation(name,func)

This creates a collation callback. A collation callback is used to establish a collation order, mostly for string comparisons and sorting purposes. name is a string with the name of the collation to be created; func is a function that accepts two string arguments, compares them and returns 0 if both strings are identical, -1 if the first argument is lower in the collation order than the second and 1 if the first argument is higher in the collation order than the second. A simple example:

        local function collate(s1,s2)
          s1=s1:lower()
          s2=s2:lower()
          if s1==s2 then return 0
          elseif s1<s2 then return -1
          else return 1 end
        end
        db:exec[=[
          CREATE TABLE test(id INTEGER PRIMARY KEY,content COLLATE CINSENS);
          INSERT INTO test VALUES(NULL,'hello world');
          INSERT INTO test VALUES(NULL,'Buenos dias');
          INSERT INTO test VALUES(NULL,'HELLO WORLD');
        ]=]
        db:create_collation('CINSENS',collate)
        for row in db:nrows('SELECT * FROM test') do print(row.id,row.content) end

db:create_function

        db:create_function(name,nargs,func[,userdata])

This function creates a callback function. Callback function are called by SQLite3 once for every row in a query. name is a string with the name of the callback function as given in an SQL statement; nargs is the number of arguments this call will provide. func is the actual Lua function that gets called once for every row; it should accept a function context (see Methods for callback contexts) plus the same number of parameters as given in nargs. If provided, userdata can be any Lua value and would be returned by the context:user_data() method. Here is an example:

        db:exec'CREATE TABLE test(col1,col2,col3)'
        db:exec'INSERT INTO test VALUES(1,2,4)'
        db:exec'INSERT INTO test VALUES(2,4,9)'
        db:exec'INSERT INTO test VALUES(3,6,16)'
        db:create_function('sum_cols',3,function(ctx,a,b,c)
          ctx:result_number(a+b+c)
        end))
        for col1,col2,col3,sum in db:urows('SELECT *,sum_cols(col1,col2,col3) FROM test') do
          util.printf('%2i+%2i+%2i=%2i\n',col1,col2,col3,sum)
        end

db:load_extension

        db:load_extension([name,[entrypoint]])

When a name is provided, loads an SQLite extension library from the named file into this database connection. The optional entrypoint is the library initialization function name; if not supplied, SQLite tries various default entrypoint names. Returns true when successful, or false and an error string otherwise.

When called with no arguments, disables the load_extension() SQL function, which is enabled as a side effect of calling db:load_extension with a name.

db:errcode

        db:errcode()
        db:error_code()

Returns the numerical result code (or extended result code) for the most recent failed call associated with database db. See Numerical error and result codes for details.

db:errmsg

        db:errmsg()
        db:error_message()

Returns a string that contains an error message for the most recent failed call associated with database db.

db:exec

        db:exec(sql[,func[,udata]])
        db:execute(sql[,func[,udata]])

Compiles and executes the SQL statement(s) given in string sql. The statements are simply executed one after the other and not stored. The function returns sqlite3.OK on success or else a numerical error code (see Numerical error and result codes).

If one or more of the SQL statements are queries, then the callback function specified in func is invoked once for each row of the query result (if func is nil, no callback is invoked). The callback receives four arguments: udata (the third parameter of the db:exec() call), the number of columns in the row, a table with the column values and another table with the column names. The callback function should return 0. If the callback returns a non-zero value then the query is aborted, all subsequent SQL statements are skipped and db:exec() returns sqlite3.ABORT. Here is a simple example:

        sql=[=[
          CREATE TABLE numbers(num1,num2,str);
          INSERT INTO numbers VALUES(1,11,"ABC");
          INSERT INTO numbers VALUES(2,22,"DEF");
          INSERT INTO numbers VALUES(3,33,"UVW");
          INSERT INTO numbers VALUES(4,44,"XYZ");
          SELECT * FROM numbers;
        ]=]
        function showrow(udata,cols,values,names)
          assert(udata=='test_udata')
          print('exec:')
          for i=1,cols do print('',names[i],values[i]) end
          return 0
        end
        db:exec(sql,showrow,'test_udata')

db:interrupt

        db:interrupt()

This function causes any pending database operation to abort and return at the next opportunity. This function returns nothing.

db:db_filename

        db:db_filename(name)

This function returns the filename associated with database name of connection db. The name may be "main" for the main database file, or the name specified after the AS keyword in an ATTACH statement for an attached database. If there is no attached database name on the database connection db, then no value is returned; if database name is a temporary or in-memory database, then an empty string is returned.

db:isopen

        db:isopen()

Returns true if database db is open, false otherwise.

db:last_insert_rowid

        db:last_insert_rowid()

This function returns the rowid of the most recent INSERT into the database. If no inserts have ever occurred, 0 is returned. (Each row in an SQLite table has a unique 64-bit signed integer key called the 'rowid'. This id is always available as an undeclared column named ROWID, OID, or _ROWID_. If the table has a column of type INTEGER PRIMARY KEY then that column is another alias for the rowid.)

If an INSERT occurs within a trigger, then the rowid of the inserted row is returned as long as the trigger is running. Once the trigger terminates, the value returned reverts to the last value inserted before the trigger fired.

db:nrows

        db:nrows(sql)

Creates an iterator that returns the successive rows selected by the SQL statement given in string sql. Each call to the iterator returns a table in which the named fields correspond to the columns in the database. Here is an example:

        db:exec[=[
          CREATE TABLE numbers(num1,num2);
          INSERT INTO numbers VALUES(1,11);
          INSERT INTO numbers VALUES(2,22);
          INSERT INTO numbers VALUES(3,33);
        ]=]
        for a in db:nrows('SELECT * FROM numbers') do table.print(a) end

This script prints:

        num2: 11
        num1: 1
        num2: 22
        num1: 2
        num2: 33
        num1: 3

db:prepare

        db:prepare(sql)

This function compiles the SQL statement in string sql into an internal representation and returns this as userdata. The returned object should be used for all further method calls in connection with this specific SQL statement (see Methods for prepared statements).

db:progress_handler

        db:progress_handler(n,func,udata)

This function installs a callback function func that is invoked periodically during long-running calls to db:exec() or stmt:step(). The progress callback is invoked once for every n internal operations, where n is the first argument to this function. udata is passed to the progress callback function each time it is invoked. If a call to db:exec() or stmt:step() results in fewer than n operations being executed, then the progress callback is never invoked. Only a single progress callback function may be registered for each opened database and a call to this function will overwrite any previously set callback function. To remove the progress callback altogether, pass nil as the second argument.

If the progress callback returns a result other than 0, then the current query is immediately terminated, any database changes are rolled back and the containing db:exec() or stmt:step() call returns sqlite3.INTERRUPT. This feature can be used to cancel long-running queries.

db:rollback_hook

        db:rollback_hook(func,udata)

This function installs a rollback_hook callback handler. func is a Lua function that is invoked by SQLite3 whenever a transaction is rolled back. This callback receives one argument: the udata argument used when the callback was installed.

See: db:commit_hook and db:update_hook

db:rows

        db:rows(sql)

Creates an iterator that returns the successive rows selected by the SQL statement given in string sql. Each call to the iterator returns a table in which the numerical indices 1 to n correspond to the selected columns 1 to n in the database. Here is an example:

        db:exec[=[
          CREATE TABLE numbers(num1,num2);
          INSERT INTO numbers VALUES(1,11);
          INSERT INTO numbers VALUES(2,22);
          INSERT INTO numbers VALUES(3,33);
        ]=]
        for a in db:rows('SELECT * FROM numbers') do table.print(a) end

This script prints:

        1: 1
        2: 11
        1: 2
        2: 22
        1: 3
        2: 33

db:total_changes

        db:total_changes()

This function returns the number of database rows that have been modified by INSERT, UPDATE or DELETE statements since the database was opened. This includes UPDATE, INSERT and DELETE statements executed as part of trigger programs. All changes are counted as soon as the statement that produces them is completed by calling either stmt:reset() or stmt:finalize().

db:trace

        db:trace(func,udata)

This function installs a trace callback handler. func is a Lua function that is called by SQLite3 just before the evaluation of an SQL statement. This callback receives two arguments: the first is the udata argument used when the callback was installed; the second is a string with the SQL statement about to be executed.

db:update_hook

        db:update_hook(func,udata)

This function installs an update_hook Data Change Notification Callback handler. func is a Lua function that is invoked by SQLite3 whenever a row is updated, inserted or deleted. This callback receives five arguments: the first is the udata argument used when the callback was installed; the second is an integer indicating the operation that caused the callback to be invoked (one of sqlite3.UPDATE, sqlite3.INSERT, or sqlite3.DELETE). The third and fourth arguments are the database and table name containing the affected row. The final callback parameter is the rowid of the row. In the case of an update, this is the rowid after the update takes place.

See: db:commit_hook and db:rollback_hook

db:urows

        db:urows(sql)

Creates an iterator that returns the successive rows selected by the SQL statement given in string sql. Each call to the iterator returns the values that correspond to the columns in the currently selected row. Here is an example:

        db:exec[=[
          CREATE TABLE numbers(num1,num2);
          INSERT INTO numbers VALUES(1,11);
          INSERT INTO numbers VALUES(2,22);
          INSERT INTO numbers VALUES(3,33);
        ]=]
        for num1,num2 in db:urows('SELECT * FROM numbers') do print(num1,num2) end

This script prints:

        1       11
        2       22
        3       33

Methods for prepared statements

After creating a prepared statement with db:prepare() the returned statement object should be used for all further calls in connection with that statement. Statement objects support the following methods.

stmt:bind

        stmt:bind(n[,value])

Binds value to statement parameter n. If the type of value is string it is bound as text. If the type of value is number, then with Lua prior to 5.3 it is bound as a double, with Lua 5.3 it is bound as an integer or double depending on its subtype using lua_isinteger. If value is a boolean then it is bound as 0 for false or 1 for true. If value is nil or missing, any previous binding is removed. The function returns sqlite3.OK on success or else a numerical error code (see Numerical error and result codes).

stmt:bind_blob

        stmt:bind_blob(n,blob)

Binds string blob (which can be a binary string) as a blob to statement parameter n. The function returns sqlite3.OK on success or else a numerical error code (see Numerical error and result codes).

stmt:bind_names

        stmt:bind_names(nametable)

Binds the values in nametable to statement parameters. If the statement parameters are named (i.e., of the form ":AAA" or "$AAA") then this function looks for appropriately named fields in nametable; if the statement parameters are not named, it looks for numerical fields 1 to the number of statement parameters. The function returns sqlite3.OK on success or else a numerical error code (see Numerical error and result codes).

stmt:bind_parameter_count

        stmt:bind_parameter_count()

Returns the largest statement parameter index in prepared statement stmt. When the statement parameters are of the forms ":AAA" or "?", then they are assigned sequentially increasing numbers beginning with one, so the value returned is the number of parameters. However if the same statement parameter name is used multiple times, each occurrence is given the same number, so the value returned is the number of unique statement parameter names.

If statement parameters of the form "?NNN" are used (where NNN is an integer) then there might be gaps in the numbering and the value returned by this interface is the index of the statement parameter with the largest index value.

stmt:bind_parameter_name

        stmt:bind_parameter_name(n)

Returns the name of the n-th parameter in prepared statement stmt. Statement parameters of the form ":AAA" or "@AAA" or "$VVV" have a name which is the string ":AAA" or "@AAA" or "$VVV". In other words, the initial ":" or "$" or "@" is included as part of the name. Parameters of the form "?" or "?NNN" have no name. The first bound parameter has an index of 1. If the value n is out of range or if the n-th parameter is nameless, then nil is returned. The function returns sqlite3.OK on success or else a numerical error code (see Numerical error and result codes)

stmt:bind_values

        stmt:bind_values(value1,value2,...,valueN)

Binds the given values to statement parameters. The function returns sqlite3.OK on success or else a numerical error code (see Numerical error and result codes).

stmt:columns

        stmt:columns()

Returns the number of columns in the result set returned by statement stmt or 0 if the statement does not return data (for example an UPDATE).

stmt:finalize

        stmt:finalize()

This function frees prepared statement stmt. If the statement was executed successfully, or not executed at all, then sqlite3.OK is returned. If execution of the statement failed then an error code is returned.

stmt:get_name

        stmt:get_name(n)

Returns the name of column n in the result set of statement stmt. (The left-most column is number 0.)

stmt:get_named_types

        stmt:get_named_types()

Returns a table with the names and types of all columns in the result set of statement stmt.

stmt:get_named_values

        stmt:get_named_values()

This function returns a table with names and values of all columns in the current result row of a query.

stmt:get_names

        stmt:get_names()

This function returns an array with the names of all columns in the result set returned by statement stmt.

stmt:get_type

        stmt:get_type(n)

Returns the type of column n in the result set of statement stmt. (The left-most column is number 0.)

stmt:get_types

        stmt:get_types()

This function returns an array with the types of all columns in the result set returned by statement stmt.

stmt:get_unames

        stmt:get_unames()

This function returns a list with the names of all columns in the result set returned by statement stmt.

stmt:get_utypes

        stmt:get_utypes()

This function returns a list with the types of all columns in the result set returned by statement stmt.

stmt:get_uvalues

        stmt:get_uvalues()

This function returns a list with the values of all columns in the current result row of a query.

stmt:get_value

        stmt:get_value(n)

Returns the value of column n in the result set of statement stmt. (The left-most column is number 0.)

stmt:get_values

        stmt:get_values()

This function returns an array with the values of all columns in the result set returned by statement stmt.

stmt:isopen

        stmt:isopen()

Returns true if stmt has not yet been finalized, false otherwise.

stmt:nrows

        stmt:nrows()

Returns an function that iterates over the names and values of the result set of statement stmt. Each iteration returns a table with the names and values for the current row. This is the prepared statement equivalent of db:nrows().

stmt:reset

        stmt:reset()

This function resets SQL statement stmt, so that it is ready to be re-executed. Any statement variables that had values bound to them using the stmt:bind*() functions retain their values.

stmt:rows

        stmt:rows()

Returns an function that iterates over the values of the result set of statement stmt. Each iteration returns an array with the values for the current row. This is the prepared statement equivalent of db:rows().

stmt:step

        stmt:step()

This function must be called to evaluate the (next iteration of the) prepared statement stmt. It will return one of the following values:

stmt:urows

        stmt:urows()

Returns an function that iterates over the values of the result set of statement stmt. Each iteration returns the values for the current row. This is the prepared statement equivalent of db:urows().

stmt:last_insert_rowid

        stmt:last_insert_rowid()

This function returns the rowid of the most recent INSERT into the database corresponding to this statement. See db:last_insert_rowid().

Methods for callback contexts

A callback context is available as a parameter inside the callback functions db:create_aggregate() and db:create_function(). It can be used to get further information about the state of a query.

context:aggregate_count

        context:aggregate_count()

Returns the number of calls to the aggregate step function.

context:get_aggregate_data

        context:get_aggregate_data()

Returns the user-definable data field for callback funtions.

context:set_aggregate_data

        context:set_aggregate_data(udata)

Set the user-definable data field for callback funtions to udata.

context:result

        context:result(res)

This function sets the result of a callback function to res. The type of the result depends on the type of res and is either a number or a string or nil. All other values will raise an error message.

context:result_null

        context:result_null()

This function sets the result of a callback function to nil. It returns nothing.

context:result_number

        context:result_number(number)
        context:result_double(number)

This function sets the result of a callback function to the value number. It returns nothing.

context:result_int

        context:result_int(number)

This function sets the result of a callback function to the integer value in number. It returns nothing.

context:result_text

        context:result_text(str)

This function sets the result of a callback function to the string in str. It returns nothing.

context:result_blob

        context:result_blob(blob)

This function sets the result of a callback function to the binary string in blob. It returns nothing.

context:result_error

        context:result_error(err)

This function sets the result of a callback function to the error value in err. It returns nothing.

context:user_data

        context:user_data()

Returns the userdata parameter given in the call to install the callback function (see db:create_aggregate() and db:create_function() for details).

Methods for Online Backup

A backup userdata is created using backup = sqlite3.backup_init(...). It is then used to step the backup, or inquire about its progress.

backup:step

        backup:step(nPages)

Returns the status of the backup after stepping nPages. It is called one or more times to transfer the data between the two databases.

backup:step(nPages) will copy up to nPages pages between the source and destination databases specified by backup userdata. If nPages is negative, all remaining source pages are copied.

If backup:step(nPages) successfully copies nPages pages and there are still more pages to be copied, then the function returns sqlite3.OK. If backup:step(nPages) successfully finishes copying all pages from source to destination, then it returns sqlite3.DONE. If an error occurs during the step, then an error code is returned. such as sqlite3.READONLY, sqlite3.NOMEM, sqlite3.BUSY, sqlite3.LOCKED, or an sqlite3.IOERR_XXX extended error code.

backup:remaining

        backup:remaining()

Returns the number of pages still to be backed up at the conclusion of the most recent step.

backup:pagecount

        backup:pagecount()

Returns the total number of pages in the source database at the conclusion of the most recent step.

backup:finish

        backup:finish()

When backup:step(nPages) has returned sqlite3.DONE, or when the application wishes to abandon the backup operation, the application should destroy the backup by calling backup:finish(). This releases all resources associated with the backup. If backup:step(nPages) has not yet returned sqlite3.DONE, then any active write-transaction on the destination database is rolled back. After the call, the backup userdata corresponds to a completed backup, and should not be used.

The value returned by backup:finish() is sqlite3.OK if no errors occurred, regardless or whether or not the backup completed. If an out-of-memory condition or IO error occurred during any prior step on the same backup, then backup:finish() returns the corresponding error code.

A return of sqlite3.BUSY or sqlite3.LOCKED from backup:step(nPages) is not a permanent error and does not affect the return value of backup:finish().

Numerical error and result codes

The following constants are defined by module sqlite3:

        OK: 0          ERROR: 1       INTERNAL: 2    PERM: 3        ABORT: 4
        BUSY: 5        LOCKED: 6      NOMEM: 7       READONLY: 8    INTERRUPT: 9
        IOERR: 10      CORRUPT: 11    NOTFOUND: 12   FULL: 13       CANTOPEN: 14
        PROTOCOL: 15   EMPTY: 16      SCHEMA: 17     TOOBIG: 18     CONSTRAINT: 19
        MISMATCH: 20   MISUSE: 21     NOLFS: 22      FORMAT: 24     RANGE: 25
        NOTADB: 26     ROW: 100       DONE: 101

plus the Authorizer Action Codes:

  CREATE_INDEX: 1         CREATE_TABLE: 2       CREATE_TEMP_INDEX: 3  CREATE_TEMP_TABLE: 4
  CREATE_TEMP_TRIGGER: 5  CREATE_TEMP_VIEW: 6   CREATE_TRIGGER: 7     CREATE_VIEW: 8
  DELETE: 9               DROP_INDEX: 10        DROP_TABLE: 11        DROP_TEMP_INDEX: 12
  DROP_TEMP_TABLE: 13     DROP_TEMP_TRIGGER: 14 DROP_TEMP_VIEW: 15    DROP_TRIGGER: 16
  DROP_VIEW: 17           INSERT: 18            PRAGMA: 19            READ: 20
  SELECT: 21              TRANSACTION: 22       UPDATE: 23            ATTACH: 24
  DETACH: 25              ALTER_TABLE: 26       REINDEX: 27           ANALYZE: 28
  CREATE_VTABLE: 29       DROP_VTABLE: 30       FUNCTION: 31          SAVEPOINT: 32

and the Open Flags:

  OPEN_READONLY           OPEN_READWRITE        OPEN_CREATE           OPEN_URI
  OPEN_MEMORY             OPEN_NOMUTEX          OPEN_FULLMUTEX        OPEN_SHAREDCACHE
  OPEN_PRIVATECACHE

For details about their exact meaning please see the SQLite3 documentation http://www.sqlite.org/.

VERSION

This is lsqlite3 version "0.9.4", also tagged as fsl_9x.

CREDITS

lsqlite3 was developed by Tiago Dionizio and Doug Currie with contributions from Thomas Lauer, Michael Roth, and Wolfgang Oertl.

This documentation is based on the "(very) preliminary" documents for the Idle-SQLite3 database module. Thanks to Thomas Lauer for making it available.

LICENSE

    /************************************************************************
    * lsqlite3                                                              *
    * Copyright (C) 2002-2016 Tiago Dionizio, Doug Currie                   *
    * All rights reserved.                                                  *
    * Author    : Tiago Dionizio <tiago.dionizio@ist.utl.pt>                *
    * Author    : Doug Currie <doug.currie@alum.mit.edu>                    *
    * Library   : lsqlite3 - an SQLite 3 database binding for Lua 5         *
    *                                                                       *
    * Permission is hereby granted, free of charge, to any person obtaining *
    * a copy of this software and associated documentation files (the       *
    * "Software"), to deal in the Software without restriction, including   *
    * without limitation the rights to use, copy, modify, merge, publish,   *
    * distribute, sublicense, and/or sell copies of the Software, and to    *
    * permit persons to whom the Software is furnished to do so, subject to *
    * the following conditions:                                             *
    *                                                                       *
    * The above copyright notice and this permission notice shall be        *
    * included in all copies or substantial portions of the Software.       *
    *                                                                       *
    * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       *
    * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    *
    * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*
    * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  *
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    ************************************************************************/