SQLite

**   If the query runs to completion without incident, SQLITE_OK is returned.
**   Or, if some error occurs before the query completes or is aborted by
**   the callback, an SQLite error code is returned.
**
**
** xSetAuxdata(pFts5, pAux, xDelete)
**
**   Save the pointer passed as the second argument as the extension functions 
**   "auxiliary data". The pointer may then be retrieved by the current or any
**   future invocation of the same fts5 extension function made as part of
**   the same MATCH query using the xGetAuxdata() API.
**
**   Each extension function is allocated a single auxiliary data slot for
**   each FTS query (MATCH expression). If the extension function is invoked 
**   more than once for a single FTS query, then all invocations share a 

**   of "first place" within the document set, but not alternative forms
**   such as "1st place". In some applications, it would be better to match
**   all instances of "first place" or "1st place" regardless of which form
**   the user specified in the MATCH query text.
**
**   There are several ways to approach this in FTS5:
**
**   <ol><li> By mapping all synonyms to a single token. In this case, the 
**            In the above example, this means that the tokenizer returns the
**            same token for inputs "first" and "1st". Say that token is in
**            fact "first", so that when the user inserts the document "I won
**            1st place" entries are added to the index for tokens "i", "won",
**            "first" and "place". If the user then queries for '1st + place',
**            the tokenizer substitutes "first" for "1st" and the query works
**            as expected.
**

/*
** CAPI3REF: Set a table filter on a Session Object.
** METHOD: sqlite3_session
**
** The second argument (xFilter) is the "filter callback". For changes to rows 
** in tables that are not attached to the Session object, the filter is called
** to determine whether changes to the table's rows should be tracked or not. 
** If xFilter returns 0, changes is not tracked. Note that once a table is 
** attached, xFilter will not be called again.
*/
void sqlite3session_table_filter(
  sqlite3_session *pSession,      /* Session object */
  int(*xFilter)(
    void *pCtx,                   /* Copy of third arg to _filter_table() */
    const char *zTab              /* Table name */

** using [sqlite3session_changeset()], then after applying that changeset to 
** database zFrom the contents of the two compatible tables would be 
** identical.
**
** It an error if database zFrom does not exist or does not contain the
** required compatible table.
**
** If the operation successful, SQLITE_OK is returned. Otherwise, an SQLite
** error code. In this case, if argument pzErrMsg is not NULL, *pzErrMsg
** may be set to point to a buffer containing an English language error 
** message. It is the responsibility of the caller to free this buffer using
** sqlite3_free().
*/
int sqlite3session_diff(
  sqlite3_session *pSession,

#define SQLITE_CHANGESETSTART_INVERT        0x0002


/*
** CAPI3REF: Advance A Changeset Iterator
** METHOD: sqlite3_changeset_iter
**
** This function may only be used with iterators created by function
** [sqlite3changeset_start()]. If it is called on an iterator passed to
** a conflict-handler callback by [sqlite3changeset_apply()], SQLITE_MISUSE
** is returned and the call has no effect.
**
** Immediately after an iterator is created by sqlite3changeset_start(), it
** does not point to any change in the changeset. Assuming the changeset
** is not empty, the first call to this function advances the iterator to

**
** If the new changeset contains changes to a table that is already present
** in the changegroup, then the number of columns and the position of the
** primary key columns for the table must be consistent. If this is not the
** case, this function fails with SQLITE_SCHEMA. If the input changeset
** appears to be corrupt and the corruption is detected, SQLITE_CORRUPT is
** returned. Or, if an out-of-memory condition occurs during processing, this
** function returns SQLITE_NOMEM. In all cases, if an error occurs the
** final contents of the changegroup is undefined.
**
** If no error occurs, SQLITE_OK is returned.
*/
int sqlite3changegroup_add(sqlite3_changegroup*, int nData, void *pData);

/*
** CAPI3REF: Obtain A Composite Changeset From A Changegroup

**   This includes the case where the UPDATE operation is attempted after 
**   an earlier call to the conflict handler function returned
**   [SQLITE_CHANGESET_REPLACE].  
** </dl>
**
** It is safe to execute SQL statements, including those that write to the
** table that the callback related to, from within the xConflict callback.
** This can be used to further customize the applications conflict
** resolution strategy.
**
** All changes made by these functions are enclosed in a savepoint transaction.
** If any other error (aside from a constraint failure when attempting to
** write to the target database) occurs, then the savepoint transaction is
** rolled back, restoring the target database to its original state, and an 
** SQLite error code returned.

/*
** CAPI3REF: Rebase a changeset
** EXPERIMENTAL
**
** Argument pIn must point to a buffer containing a changeset nIn bytes
** in size. This function allocates and populates a buffer with a copy
** of the changeset rebased rebased according to the configuration of the
** rebaser object passed as the first argument. If successful, (*ppOut)
** is set to point to the new buffer containing the rebased changeset and 
** (*pnOut) to its size in bytes and SQLITE_OK returned. It is the
** responsibility of the caller to eventually free the new buffer using
** sqlite3_free(). Otherwise, if an error occurs, (*ppOut) and (*pnOut)
** are set to zero and an SQLite error code returned.
*/

** file control occurs at the beginning of pragma statement analysis and so
** it is able to override built-in [PRAGMA] statements.
**
** <li>[[SQLITE_FCNTL_BUSYHANDLER]]
** ^The [SQLITE_FCNTL_BUSYHANDLER]
** file-control may be invoked by SQLite on the database file handle
** shortly after it is opened in order to provide a custom VFS with access
** to the connections busy-handler callback. The argument is of type (void **)
** - an array of two (void *) values. The first (void *) actually points
** to a function of type (int (*)(void *)). In order to invoke the connections
** busy-handler, this function should be invoked with the second (void *) in
** the array as the only argument. If it returns non-zero, then the operation
** should be retried. If it returns zero, the custom VFS should abandon the
** current operation.
**
** <li>[[SQLITE_FCNTL_TEMPFILENAME]]
** ^Application can invoke the [SQLITE_FCNTL_TEMPFILENAME] file-control
** to have SQLite generate a
** temporary filename using the same algorithm that is followed to generate
** temporary filenames for TEMP tables and other internal uses.  The
** argument should be a char** which will be filled with the filename
** written into memory obtained from [sqlite3_malloc()].  The caller should
** invoke [sqlite3_free()] on the result to avoid a memory leak.
**

** connection or through transactions committed by separate database
** connections possibly in other processes. The [sqlite3_total_changes()]
** interface can be used to find if any database on the connection has changed,
** but that interface responds to changes on TEMP as well as MAIN and does
** not provide a mechanism to detect changes to MAIN only.  Also, the
** [sqlite3_total_changes()] interface responds to internal changes only and
** omits changes made by other database connections.  The
** [PRAGMA data_version] command provide a mechanism to detect changes to
** a single attached database that occur due to other database connections,
** but omits changes implemented by the database connection on which it is
** called.  This file control is the only mechanism to detect changes that
** happen either internally or externally and that are associated with
** a particular attached database.
** </ul>
*/

** the end.  Each time such an extension occurs, the iVersion field
** is incremented.  The iVersion value started out as 1 in
** SQLite [version 3.5.0] on [dateof:3.5.0], then increased to 2
** with SQLite [version 3.7.0] on [dateof:3.7.0], and then increased
** to 3 with SQLite [version 3.7.6] on [dateof:3.7.6].  Additional fields
** may be appended to the sqlite3_vfs object and the iVersion value
** may increase again in future versions of SQLite.
** Note that the structure
** of the sqlite3_vfs object changes in the transition from
** SQLite [version 3.5.9] to [version 3.6.0] on [dateof:3.6.0]
** and yet the iVersion field was not modified.
**
** The szOsFile field is the size of the subclassed [sqlite3_file]
** structure used by this VFS.  mxPathname is the maximum length of
** a pathname in this VFS.
**
** Registered sqlite3_vfs objects are kept on a linked list formed by
** the pNext pointer.  The [sqlite3_vfs_register()]

** API.  The SQLITE_OPEN_EXCLUSIVE flag, when paired with the 
** SQLITE_OPEN_CREATE, is used to indicate that file should always
** be created, and that it is an error if it already exists.
** It is <i>not</i> used to indicate the file should be opened 
** for exclusive access.
**
** ^At least szOsFile bytes of memory are allocated by SQLite
** to hold the  [sqlite3_file] structure passed as the third
** argument to xOpen.  The xOpen method does not have to
** allocate the structure; it should just fill it in.  Note that
** the xOpen method must set the sqlite3_file.pMethods to either
** a valid [sqlite3_io_methods] object or to NULL.  xOpen must do
** this even if the open fails.  SQLite expects that the sqlite3_file.pMethods
** element will be valid after xOpen returns regardless of the success
** or failure of the xOpen call.

** allocators round up memory allocations at least to the next multiple
** of 8.  Some allocators round up to a larger multiple or to a power of 2.
** Every memory allocation request coming in through [sqlite3_malloc()]
** or [sqlite3_realloc()] first calls xRoundup.  If xRoundup returns 0, 
** that causes the corresponding memory allocation to fail.
**
** The xInit method initializes the memory allocator.  For example,
** it might allocate any require mutexes or initialize internal data
** structures.  The xShutdown method is invoked (indirectly) by
** [sqlite3_shutdown()] and should deallocate any resources acquired
** by xInit.  The pAppData pointer is used as the only parameter to
** xInit and xShutdown.
**
** SQLite holds the [SQLITE_MUTEX_STATIC_MASTER] mutex when it invokes
** the xInit method, so the xInit method need not be threadsafe.  The

** <dd> The SQLITE_CONFIG_SCRATCH option is no longer used.
** </dd>
**
** [[SQLITE_CONFIG_PAGECACHE]] <dt>SQLITE_CONFIG_PAGECACHE</dt>
** <dd> ^The SQLITE_CONFIG_PAGECACHE option specifies a memory pool
** that SQLite can use for the database page cache with the default page
** cache implementation.  
** This configuration option is a no-op if an application-define page
** cache implementation is loaded using the [SQLITE_CONFIG_PCACHE2].
** ^There are three arguments to SQLITE_CONFIG_PAGECACHE: A pointer to
** 8-byte aligned memory (pMem), the size of each page cache line (sz),
** and the number of cache lines (N).
** The sz argument should be the size of the largest database page
** (a power of two between 512 and 65536) plus some extra bytes for each
** page header.  ^The number of extra bytes needed by the page header

** additional information. This feature can also be turned on and off
** using the [PRAGMA legacy_alter_table] statement.
** </dd>
**
** [[SQLITE_DBCONFIG_DQS_DML]]
** <dt>SQLITE_DBCONFIG_DQS_DML</td>
** <dd>The SQLITE_DBCONFIG_DQS_DML option activates or deactivates
** the legacy [double-quoted string literal] misfeature for DML statement
** only, that is DELETE, INSERT, SELECT, and UPDATE statements. The
** default value of this setting is determined by the [-DSQLITE_DQS]
** compile-time option.
** </dd>
**
** [[SQLITE_DBCONFIG_DQS_DDL]]
** <dt>SQLITE_DBCONFIG_DQS_DDL</td>

** ^If the interrupted SQL operation is an INSERT, UPDATE, or DELETE
** that is inside an explicit transaction, then the entire transaction
** will be rolled back automatically.
**
** ^The sqlite3_interrupt(D) call is in effect until all currently running
** SQL statements on [database connection] D complete.  ^Any new SQL statements
** that are started after the sqlite3_interrupt() call and before the 
** running statements reaches zero are interrupted as if they had been
** running prior to the sqlite3_interrupt() call.  ^New SQL statements
** that are started after the running statement count reaches zero are
** not effected by the sqlite3_interrupt().
** ^A call to sqlite3_interrupt(D) that occurs when there are no running
** SQL statements is a no-op and has no effect on SQL statements
** that are started after the sqlite3_interrupt() call returns.
*/

**        Name        | Age
**        -----------------------
**        Alice       | 43
**        Bob         | 28
**        Cindy       | 21
** </pre></blockquote>
**
** There are two column (M==2) and three rows (N==3).  Thus the
** result table has 8 entries.  Suppose the result table is stored
** in an array names azResult.  Then azResult holds this content:
**
** <blockquote><pre>
**        azResult&#91;0] = "Name";
**        azResult&#91;1] = "Age";
**        azResult&#91;2] = "Alice";
**        azResult&#91;3] = "43";
**        azResult&#91;4] = "Bob";

**
** ^The memory returned by sqlite3_malloc(), sqlite3_realloc(),
** sqlite3_malloc64(), and sqlite3_realloc64()
** is always aligned to at least an 8 byte boundary, or to a
** 4 byte boundary if the [SQLITE_4_BYTE_ALIGNED_MALLOC] compile-time
** option is used.
**
** In SQLite version 3.5.0 and 3.5.1, it was possible to define
** the SQLITE_OMIT_MEMORY_ALLOCATION which would cause the built-in
** implementation of these routines to be omitted.  That capability
** is no longer provided.  Only built-in memory allocators can be used.
**
** Prior to SQLite version 3.7.10, the Windows OS interface layer called
** the system malloc() and free() directly when converting
** filenames between the UTF-8 encoding used by SQLite
** and whatever filename encoding is used by the particular Windows
** installation.  Memory allocation errors were detected, but
** they were reported back as [SQLITE_CANTOPEN] or
** [SQLITE_IOERR] rather than [SQLITE_NOMEM].
**
** The pointer arguments to [sqlite3_free()] and [sqlite3_realloc()]
** must be either NULL or else pointers obtained from a prior
** invocation of [sqlite3_malloc()] or [sqlite3_realloc()] that have
** not yet been released.
**
** The application must not read or write any part of
** a block of memory after it has been released using

/*
** CAPI3REF: Pseudo-Random Number Generator
**
** SQLite contains a high-quality pseudo-random number generator (PRNG) used to
** select random [ROWID | ROWIDs] when inserting new records into a table that
** already uses the largest possible [ROWID].  The PRNG is also used for
** the build-in random() and randomblob() SQL functions.  This interface allows
** applications to access the same PRNG for other purposes.
**
** ^A call to this routine stores N bytes of randomness into buffer P.
** ^The P parameter can be a NULL pointer.
**
** ^If this routine has not been previously called or if the previous
** call had N less than one or a NULL pointer for P, then the PRNG is

**
** If F is the database filename pointer passed into the xOpen() method of 
** a VFS implementation when the flags parameter to xOpen() has one or 
** more of the [SQLITE_OPEN_URI] or [SQLITE_OPEN_MAIN_DB] bits set and
** P is the name of the query parameter, then
** sqlite3_uri_parameter(F,P) returns the value of the P
** parameter if it exists or a NULL pointer if P does not appear as a 
** query parameter on F.  If P is a query parameter of F
** has no explicit value, then sqlite3_uri_parameter(F,P) returns
** a pointer to an empty string.
**
** The sqlite3_uri_boolean(F,P,B) routine assumes that P is a boolean
** parameter and returns true (1) or false (0) according to the value
** of P.  The sqlite3_uri_boolean(F,P,B) routine returns true (1) if the
** value of query parameter P is one of "yes", "true", or "on" in any
** case or if the value begins with a non-zero number.  The 
** sqlite3_uri_boolean(F,P,B) routines returns false (0) if the value of
** query parameter P is one of "no", "false", or "off" in any case or
** if the value begins with a numeric zero.  If P is not a query
** parameter on F or if the value of P is does not match any of the
** above, then sqlite3_uri_boolean(F,P,B) returns (B!=0).
**
** The sqlite3_uri_int64(F,P,D) routine converts the value of P into a
** 64-bit signed integer and returns that integer, or D if P does not
** exist.  If the value of P is something other than an integer, then
** zero is returned.
** 

** [sqlite3_step()] would only return a generic [SQLITE_ERROR] result code
** and the application would have to make a second call to [sqlite3_reset()]
** in order to find the underlying cause of the problem. With the "v2" prepare
** interfaces, the underlying reason for the error is returned immediately.
** </li>
**
** <li>
** ^If the specific value bound to [parameter | host parameter] in the 
** WHERE clause might influence the choice of query plan for a statement,
** then the statement will be automatically recompiled, as if there had been 
** a schema change, on the first  [sqlite3_step()] call following any change
** to the [sqlite3_bind_text | bindings] of that [parameter]. 
** ^The specific value of WHERE-clause [parameter] might influence the 
** choice of query plan if the parameter is the left-hand side of a [LIKE]
** or [GLOB] operator or if the parameter is compared to an indexed column
** and the [SQLITE_ENABLE_STAT4] compile-time option is enabled.
** </li>
** </ol>
**
** <p>^sqlite3_prepare_v3() differs from sqlite3_prepare_v2() only in having

** ^The first argument to these interfaces is a [prepared statement].
** ^These functions return information about the Nth result column returned by
** the statement, where N is the second function argument.
** ^The left-most column is column 0 for these routines.
**
** ^If the Nth column returned by the statement is an expression or
** subquery and is not a column value, then all of these functions return
** NULL.  ^These routine might also return NULL if a memory allocation error
** occurs.  ^Otherwise, they return the name of the attached database, table,
** or column that query result column was extracted from.
**
** ^As with all other SQLite APIs, those whose names end with "16" return
** UTF-16 encoded strings and the other functions return UTF-8.
**
** ^These APIs are only available if the library was compiled with the
** [SQLITE_ENABLE_COLUMN_METADATA] C-preprocessor symbol.
**
** If two or more threads call one or more of these routines against the same
** prepared statement and column at the same time then the results are
** undefined.
**
** If two or more threads call one or more
** [sqlite3_column_database_name | column metadata interfaces]
** for the same [prepared statement] and result column
** at the same time then the results are undefined.
*/
const char *sqlite3_column_database_name(sqlite3_stmt*,int);
const void *sqlite3_column_database_name16(sqlite3_stmt*,int);

/*
** CAPI3REF: Number of columns in a result set
** METHOD: sqlite3_stmt
**
** ^The sqlite3_data_count(P) interface returns the number of columns in the
** current row of the result set of [prepared statement] P.
** ^If prepared statement P does not have results ready to return
** (via calls to the [sqlite3_column_int | sqlite3_column_*()] of
** interfaces) then sqlite3_data_count(P) returns 0.
** ^The sqlite3_data_count(P) routine also returns 0 if P is a NULL pointer.
** ^The sqlite3_data_count(P) routine returns 0 if the previous call to
** [sqlite3_step](P) returned [SQLITE_DONE].  ^The sqlite3_data_count(P)
** will return non-zero if previous call to [sqlite3_step](P) returned
** [SQLITE_ROW], except in the case of the [PRAGMA incremental_vacuum]
** where it always returns zero since each step of that multi-step

** CAPI3REF: Function Flags
**
** These constants may be ORed together with the 
** [SQLITE_UTF8 | preferred text encoding] as the fourth argument
** to [sqlite3_create_function()], [sqlite3_create_function16()], or
** [sqlite3_create_function_v2()].
**
** The SQLITE_DETERMINISTIC flag means that the new function will always
** maps the same inputs into the same output.  The abs() function is
** deterministic, for example, but randomblob() is not.



**
** The SQLITE_DIRECTONLY flag means that the function may only be invoked
** from top-level SQL, and cannot be used in VIEWs or TRIGGERs.  This is
** a security feature which is recommended for all 
** [application-defined SQL functions] that have side-effects.  This flag 
** prevents an attacker from adding triggers and views to a schema then 
** tricking a high-privilege application into causing unintended side-effects

** <td>&rarr;&nbsp;&nbsp;<td>True if value originated from a [bound parameter]
** </table></blockquote>
**
** <b>Details:</b>
**
** These routines extract type, size, and content information from
** [protected sqlite3_value] objects.  Protected sqlite3_value objects
** are used to pass parameter information into implementation of
** [application-defined SQL functions] and [virtual tables].
**
** These routines work only with [protected sqlite3_value] objects.
** Any attempt to use these routines on an [unprotected sqlite3_value]
** is not threadsafe.
**
** ^These routines work just like the corresponding [column access functions]
** except that these routines take a single [protected sqlite3_value] object

** to be a NULL value.  If sqlite3_value_nochange(X) is invoked anywhere other
** than within an [xUpdate] method call for an UPDATE statement, then
** the return value is arbitrary and meaningless.
**
** ^The sqlite3_value_frombind(X) interface returns non-zero if the
** value X originated from one of the [sqlite3_bind_int|sqlite3_bind()]
** interfaces.  ^If X comes from an SQL literal value, or a table column,
** and expression, then sqlite3_value_frombind(X) returns zero.
**
** Please pay particular attention to the fact that the pointer returned
** from [sqlite3_value_blob()], [sqlite3_value_text()], or
** [sqlite3_value_text16()] can be invalidated by a subsequent call to
** [sqlite3_value_bytes()], [sqlite3_value_bytes16()], [sqlite3_value_text()],
** or [sqlite3_value_text16()].
**

** CAPI3REF: Obtain Aggregate Function Context
** METHOD: sqlite3_context
**
** Implementations of aggregate SQL functions use this
** routine to allocate memory for storing their state.
**
** ^The first time the sqlite3_aggregate_context(C,N) routine is called 
** for a particular aggregate function, SQLite
** allocates N of memory, zeroes out that memory, and returns a pointer
** to the new memory. ^On second and subsequent calls to
** sqlite3_aggregate_context() for the same aggregate function instance,
** the same buffer is returned.  Sqlite3_aggregate_context() is normally
** called once for each invocation of the xStep callback and then one
** last time when the xFinal callback is invoked.  ^(When no rows match
** an aggregate query, the xStep() callback of the aggregate function
** implementation is never called and xFinal() is called exactly once.
** In those cases, sqlite3_aggregate_context() might be called for the
** first time from within xFinal().)^
**
** ^The sqlite3_aggregate_context(C,N) routine returns a NULL pointer 
** when first called if N is less than or equal to zero or if a memory
** allocate error occurs.
**
** ^(The amount of space allocated by sqlite3_aggregate_context(C,N) is
** determined by the N parameter on first successful call.  Changing the
** value of N in subsequent call to sqlite3_aggregate_context() within
** the same aggregate function instance will not resize the memory
** allocation.)^  Within the xFinal callback, it is customary to set
** N=0 in calls to sqlite3_aggregate_context(C,N) so that no 
** pointless memory allocations occur.
**
** ^SQLite automatically frees the memory allocated by 
** sqlite3_aggregate_context() when the aggregate query concludes.

** <li> If A==B then B==A.
** <li> If A==B and B==C then A==C.
** <li> If A&lt;B THEN B&gt;A.
** <li> If A&lt;B and B&lt;C then A&lt;C.
** </ol>
**
** If a collating function fails any of the above constraints and that
** collating function is  registered and used, then the behavior of SQLite
** is undefined.
**
** ^The sqlite3_create_collation_v2() works like sqlite3_create_collation()
** with the addition that the xDestroy callback is invoked on pArg when
** the collating function is deleted.
** ^Collating functions are deleted when they are overridden by later
** calls to the collation creation functions or when the

*/
sqlite3 *sqlite3_db_handle(sqlite3_stmt*);

/*
** CAPI3REF: Return The Filename For A Database Connection
** METHOD: sqlite3
**
** ^The sqlite3_db_filename(D,N) interface returns a pointer to a filename
** associated with database N of connection D.  ^The main database file
** has the name "main".  If there is no attached database N on the database
** connection D, or if database N is a temporary or in-memory database, then
** this function will return either a NULL pointer or an empty string.




**
** ^The filename returned by this function is the output of the
** xFullPathname method of the [VFS].  ^In other words, the filename
** will be an absolute pathname, even if the filename used
** to open the database originally was a URI or relative pathname.
*/
const char *sqlite3_db_filename(sqlite3 *db, const char *zDbName);

** ^Cache sharing is enabled and disabled for an entire process.
** This is a change as of SQLite [version 3.5.0] ([dateof:3.5.0]). 
** In prior versions of SQLite,
** sharing was enabled or disabled for each thread separately.
**
** ^(The cache sharing mode set by this interface effects all subsequent
** calls to [sqlite3_open()], [sqlite3_open_v2()], and [sqlite3_open16()].
** Existing database connections continue use the sharing mode
** that was in effect at the time they were opened.)^
**
** ^(This routine returns [SQLITE_OK] if shared cache was enabled or disabled
** successfully.  An [error code] is returned otherwise.)^
**
** ^Shared cache is disabled by default. But this might change in
** future releases of SQLite.  Applications that care about shared
** cache setting should set it explicitly.




**
** Note: This method is disabled on MacOS X 10.7 and iOS version 5.0
** and will always return SQLITE_MISUSE. On those systems, 
** shared cache mode should be enabled per-database connection via 
** [sqlite3_open_v2()] with [SQLITE_OPEN_SHAREDCACHE].
**
** This interface is threadsafe on processors where writing a

**
** ^(The sqlite3_table_column_metadata(X,D,T,C,....) routine returns
** information about column C of table T in database D
** on [database connection] X.)^  ^The sqlite3_table_column_metadata()
** interface returns SQLITE_OK and fills in the non-NULL pointers in
** the final five arguments with appropriate values if the specified
** column exists.  ^The sqlite3_table_column_metadata() interface returns
** SQLITE_ERROR and if the specified column does not exist.
** ^If the column-name parameter to sqlite3_table_column_metadata() is a
** NULL pointer, then this routine simply checks for the existence of the
** table and returns SQLITE_OK if the table exists and SQLITE_ERROR if it
** does not.  If the table name parameter T in a call to
** sqlite3_table_column_metadata(X,D,T,C,...) is NULL then the result is
** undefined behavior.
**

**
** ^This interface enables or disables both the C-API
** [sqlite3_load_extension()] and the SQL function [load_extension()].
** ^(Use [sqlite3_db_config](db,[SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION],..)
** to enable or disable only the C-API.)^
**
** <b>Security warning:</b> It is recommended that extension loading
** be disabled using the [SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION] method
** rather than this interface, so the [load_extension()] SQL function
** remains disabled. This will prevent SQL injections from giving attackers
** access to extension loading capabilities.
*/
int sqlite3_enable_load_extension(sqlite3 *db, int onoff);

/*

typedef struct sqlite3_module sqlite3_module;

/*
** CAPI3REF: Virtual Table Object
** KEYWORDS: sqlite3_module {virtual table module}
**
** This structure, sometimes called a "virtual table module", 
** defines the implementation of a [virtual tables].  
** This structure consists mostly of methods for the module.
**
** ^A virtual table module is created by filling in a persistent
** instance of this structure and passing a pointer to that instance
** to [sqlite3_create_module()] or [sqlite3_create_module_v2()].
** ^The registration remains valid until it is replaced by a different
** module or until the [database connection] closes.  The content

** the xUpdate method are automatically rolled back by SQLite.
**
** IMPORTANT: The estimatedRows field was added to the sqlite3_index_info
** structure for SQLite [version 3.8.2] ([dateof:3.8.2]). 
** If a virtual table extension is
** used with an SQLite version earlier than 3.8.2, the results of attempting 
** to read or write the estimatedRows field are undefined (but are likely 
** to included crashing the application). The estimatedRows field should
** therefore only be used if [sqlite3_libversion_number()] returns a
** value greater than or equal to 3008002. Similarly, the idxFlags field
** was added for [version 3.9.0] ([dateof:3.9.0]). 
** It may therefore only be used if
** sqlite3_libversion_number() returns a value greater than or equal to
** 3009000.
*/

** these bits.
*/
#define SQLITE_INDEX_SCAN_UNIQUE      1     /* Scan visits at most 1 row */

/*
** CAPI3REF: Virtual Table Constraint Operator Codes
**
** These macros defined the allowed values for the
** [sqlite3_index_info].aConstraint[].op field.  Each value represents
** an operator that is part of a constraint term in the wHERE clause of
** a query that uses a [virtual table].
*/
#define SQLITE_INDEX_CONSTRAINT_EQ         2
#define SQLITE_INDEX_CONSTRAINT_GT         4
#define SQLITE_INDEX_CONSTRAINT_LE         8

**   <li>  [sqlite3_mutex_held()] </li>
**   <li>  [sqlite3_mutex_notheld()] </li>
** </ul>)^
**
** The only difference is that the public sqlite3_XXX functions enumerated
** above silently ignore any invocations that pass a NULL pointer instead
** of a valid mutex handle. The implementations of the methods defined
** by this structure are not required to handle this case, the results
** of passing a NULL pointer instead of a valid mutex handle are undefined
** (i.e. it is acceptable to provide an implementation that segfaults if
** it is passed a NULL pointer).
**
** The xMutexInit() method must be threadsafe.  It must be harmless to
** invoke xMutexInit() multiple times within the same process and without
** intervening calls to xMutexEnd().  Second and subsequent calls to

** returned value includes allocations that overflowed because they
** where too large (they were larger than the "sz" parameter to
** [SQLITE_CONFIG_PAGECACHE]) and allocations that overflowed because
** no space was left in the page cache.</dd>)^
**
** [[SQLITE_STATUS_PAGECACHE_SIZE]] ^(<dt>SQLITE_STATUS_PAGECACHE_SIZE</dt>
** <dd>This parameter records the largest memory allocation request
** handed to [pagecache memory allocator].  Only the value returned in the
** *pHighwater parameter to [sqlite3_status()] is of interest.  
** The value written into the *pCurrent parameter is undefined.</dd>)^
**
** [[SQLITE_STATUS_SCRATCH_USED]] <dt>SQLITE_STATUS_SCRATCH_USED</dt>
** <dd>No longer used.</dd>
**
** [[SQLITE_STATUS_SCRATCH_OVERFLOW]] ^(<dt>SQLITE_STATUS_SCRATCH_OVERFLOW</dt>

**
** <dl>
** [[SQLITE_DBSTATUS_LOOKASIDE_USED]] ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_USED</dt>
** <dd>This parameter returns the number of lookaside memory slots currently
** checked out.</dd>)^
**
** [[SQLITE_DBSTATUS_LOOKASIDE_HIT]] ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_HIT</dt>
** <dd>This parameter returns the number malloc attempts that were 
** satisfied using lookaside memory. Only the high-water value is meaningful;
** the current value is always zero.)^
**
** [[SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE]]
** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE</dt>
** <dd>This parameter returns the number malloc attempts that might have
** been satisfied using lookaside memory but failed due to the amount of

**
** [[SQLITE_DBSTATUS_CACHE_SPILL]] ^(<dt>SQLITE_DBSTATUS_CACHE_SPILL</dt>
** <dd>This parameter returns the number of dirty cache entries that have
** been written to disk in the middle of a transaction due to the page
** cache overflowing. Transactions are more efficient if they are written
** to disk all at once. When pages spill mid-transaction, that introduces
** additional overhead. This parameter can be used help identify
** inefficiencies that can be resolve by increasing the cache size.
** </dd>
**
** [[SQLITE_DBSTATUS_DEFERRED_FKS]] ^(<dt>SQLITE_DBSTATUS_DEFERRED_FKS</dt>
** <dd>This parameter returns zero for the current value if and only if
** all foreign key constraints (deferred or immediate) have been
** resolved.)^  ^The highwater mark is always 0.
** </dd>

** to 2147483647.  The number of virtual machine operations can be 
** used as a proxy for the total work done by the prepared statement.
** If the number of virtual machine operations exceeds 2147483647
** then the value returned by this statement status code is undefined.
**
** [[SQLITE_STMTSTATUS_REPREPARE]] <dt>SQLITE_STMTSTATUS_REPREPARE</dt>
** <dd>^This is the number of times that the prepare statement has been
** automatically regenerated due to schema changes or change to 
** [bound parameters] that might affect the query plan.
**
** [[SQLITE_STMTSTATUS_RUN]] <dt>SQLITE_STMTSTATUS_RUN</dt>
** <dd>^This is the number of times that the prepared statement has
** been run.  A single "run" for the purposes of this counter is one
** or more calls to [sqlite3_step()] followed by a call to [sqlite3_reset()].
** The counter is incremented on the first [sqlite3_step()] call of each

**                 Otherwise return NULL.
** <tr><td> 2 <td> Make every effort to allocate a new page.  Only return
**                 NULL if allocating a new page is effectively impossible.
** </table>
**
** ^(SQLite will normally invoke xFetch() with a createFlag of 0 or 1.  SQLite
** will only use a createFlag of 2 after a prior call with a createFlag of 1
** failed.)^  In between the to xFetch() calls, SQLite may
** attempt to unpin one or more cache pages by spilling the content of
** pinned pages to disk and synching the operating system disk cache.
**
** [[the xUnpin() page cache method]]
** ^xUnpin() is called by SQLite with a pointer to a currently pinned page
** as its second argument.  If the third parameter, discard, is non-zero,
** then the page must be evicted from the cache.

** identity of the database connection (the blocking connection) that
** has locked the required resource is stored internally. ^After an 
** application receives an SQLITE_LOCKED error, it may call the
** sqlite3_unlock_notify() method with the blocked connection handle as 
** the first argument to register for a callback that will be invoked
** when the blocking connections current transaction is concluded. ^The
** callback is invoked from within the [sqlite3_step] or [sqlite3_close]
** call that concludes the blocking connections transaction.
**
** ^(If sqlite3_unlock_notify() is called in a multi-threaded application,
** there is a chance that the blocking connection will have already
** concluded its transaction by the time sqlite3_unlock_notify() is invoked.
** If this happens, then the specified callback is invoked immediately,
** from within the call to sqlite3_unlock_notify().)^
**

** When an unlock-notify callback is registered, the application provides a 
** single void* pointer that is passed to the callback when it is invoked.
** However, the signature of the callback function allows SQLite to pass
** it an array of void* context pointers. The first argument passed to
** an unlock-notify callback is a pointer to an array of void* pointers,
** and the second is the number of entries in the array.
**
** When a blocking connections transaction is concluded, there may be
** more than one blocked connection that has registered for an unlock-notify
** callback. ^If two or more such blocked connections have specified the
** same callback function, then instead of invoking the callback function
** multiple times, it is invoked once with the set of void* context pointers
** specified by the blocked connections bundled together into an array.
** This gives the application an opportunity to prioritize any actions 
** related to the set of unblocked database connections.

**
** When the value returned to V is a string, space to hold that string is
** managed by the prepared statement S and will be automatically freed when
** S is finalized.
**
** <dl>
** [[SQLITE_SCANSTAT_NLOOP]] <dt>SQLITE_SCANSTAT_NLOOP</dt>
** <dd>^The [sqlite3_int64] variable pointed to by the T parameter will be
** set to the total number of times that the X-th loop has run.</dd>
**
** [[SQLITE_SCANSTAT_NVISIT]] <dt>SQLITE_SCANSTAT_NVISIT</dt>
** <dd>^The [sqlite3_int64] variable pointed to by the T parameter will be set
** to the total number of rows examined by all iterations of the X-th loop.</dd>
**
** [[SQLITE_SCANSTAT_EST]] <dt>SQLITE_SCANSTAT_EST</dt>
** <dd>^The "double" variable pointed to by the T parameter will be set to the
** query planner's estimate for the average number of rows output from each
** iteration of the X-th loop.  If the query planner's estimates was accurate,
** then this value will approximate the quotient NVISIT/NLOOP and the
** product of this value for all prior loops with the same SELECTID will
** be the NLOOP value for the current loop.
**
** [[SQLITE_SCANSTAT_NAME]] <dt>SQLITE_SCANSTAT_NAME</dt>
** <dd>^The "const char *" variable pointed to by the T parameter will be set
** to a zero-terminated UTF-8 string containing the name of the index or table
** used for the X-th loop.
**
** [[SQLITE_SCANSTAT_EXPLAIN]] <dt>SQLITE_SCANSTAT_EXPLAIN</dt>
** <dd>^The "const char *" variable pointed to by the T parameter will be set
** to a zero-terminated UTF-8 string containing the [EXPLAIN QUERY PLAN]
** description for the X-th loop.
**
** [[SQLITE_SCANSTAT_SELECTID]] <dt>SQLITE_SCANSTAT_SELECT</dt>
** <dd>^The "int" variable pointed to by the T parameter will be set to the
** "select-id" for the X-th loop.  The select-id identifies which query or
** subquery the loop is part of.  The main query has a select-id of zero.
** The select-id is the same value as is output in the first column
** of an [EXPLAIN QUERY PLAN] query.
** </dl>
*/
#define SQLITE_SCANSTAT_NLOOP    0