/ Check-in [9111ac69]
Login
SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Attempt to improve documentation on sqlite3_column_ and sqlite3_value_ interfaces.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA3-256: 9111ac69bf307997e590bc9459222661fc79f549b3c493168a654a5046e6e4ad
User & Date: drh 2017-07-03 17:37:04
Context
2017-07-03
20:19
Fix a bug in lsm queries on levels undergoing incremental an merge that contain range-delete markers. check-in: b2c24879 user: dan tags: trunk
17:37
Attempt to improve documentation on sqlite3_column_ and sqlite3_value_ interfaces. check-in: 9111ac69 user: drh tags: trunk
09:00
Add more tests for LSM log file recovery. Fix a problem in recovering log files that contain range deletes. check-in: e34eafd4 user: dan tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/sqlite.h.in.

4263
4264
4265
4266
4267
4268
4269






















4270
4271
4272
4273
4274
4275
4276
....
4285
4286
4287
4288
4289
4290
4291






4292
4293
4294
4295
4296
4297
4298



4299
4300




4301
4302
4303
4304
4305
4306
4307
....
4331
4332
4333
4334
4335
4336
4337




4338
4339

4340
4341
4342
4343
4344
4345
4346
4347
....
4405
4406
4407
4408
4409
4410
4411
4412
4413
4414
4415
4416
4417
4418
4419
4420
4421
4422
4423
4424
4425
4426
4427
4428
4429

4430

4431
4432
4433
4434
4435
4436
4437
4438
....
4658
4659
4660
4661
4662
4663
4664
4665
4666
4667



















4668
4669
4670
4671
4672



4673
4674
4675


4676
4677
4678
4679
4680
4681
4682
4683
4684
4685
4686
....
4712
4713
4714
4715
4716
4717
4718
4719
4720
4721
4722
4723
4724
4725
4726
4727


4728
4729
4730
4731
4732
4733
4734
#endif
#define SQLITE3_TEXT     3

/*
** CAPI3REF: Result Values From A Query
** KEYWORDS: {column access functions}
** METHOD: sqlite3_stmt






















**
** ^These routines return information about a single column of the current
** result row of a query.  ^In every case the first argument is a pointer
** to the [prepared statement] that is being evaluated (the [sqlite3_stmt*]
** that was returned from [sqlite3_prepare_v3()] or one of its variants)
** and the second argument is the index of the column for which information
** should be returned. ^The leftmost column of the result set has the index 0.
................................................................................
** If any of these routines are called after [sqlite3_reset()] or
** [sqlite3_finalize()] or after [sqlite3_step()] has returned
** something other than [SQLITE_ROW], the results are undefined.
** If [sqlite3_step()] or [sqlite3_reset()] or [sqlite3_finalize()]
** are called from a different thread while any of these routines
** are pending, then the results are undefined.
**






** ^The sqlite3_column_type() routine returns the
** [SQLITE_INTEGER | datatype code] for the initial data type
** of the result column.  ^The returned value is one of [SQLITE_INTEGER],
** [SQLITE_FLOAT], [SQLITE_TEXT], [SQLITE_BLOB], or [SQLITE_NULL].  The value
** returned by sqlite3_column_type() is only meaningful if no type
** conversions have occurred as described below.  After a type conversion,
** the value returned by sqlite3_column_type() is undefined.  Future



** versions of SQLite may change the behavior of sqlite3_column_type()
** following a type conversion.




**
** ^If the result is a BLOB or UTF-8 string then the sqlite3_column_bytes()
** routine returns the number of bytes in that BLOB or string.
** ^If the result is a UTF-16 string, then sqlite3_column_bytes() converts
** the string to UTF-8 and then returns the number of bytes.
** ^If the result is a numeric value then sqlite3_column_bytes() uses
** [sqlite3_snprintf()] to convert that value to a UTF-8 string and returns
................................................................................
** [unprotected sqlite3_value] object.  In a multithreaded environment,
** an unprotected sqlite3_value object may only be used safely with
** [sqlite3_bind_value()] and [sqlite3_result_value()].
** If the [unprotected sqlite3_value] object returned by
** [sqlite3_column_value()] is used in any other way, including calls
** to routines like [sqlite3_value_int()], [sqlite3_value_text()],
** or [sqlite3_value_bytes()], the behavior is not threadsafe.




**
** These routines attempt to convert the value where appropriate.  ^For

** example, if the internal representation is FLOAT and a text result
** is requested, [sqlite3_snprintf()] is used internally to perform the
** conversion automatically.  ^(The following table details the conversions
** that are applied:
**
** <blockquote>
** <table border="1">
** <tr><th> Internal<br>Type <th> Requested<br>Type <th>  Conversion
................................................................................
** to sqlite3_column_text() or sqlite3_column_blob() with calls to
** sqlite3_column_bytes16(), and do not mix calls to sqlite3_column_text16()
** with calls to sqlite3_column_bytes().
**
** ^The pointers returned are valid until a type conversion occurs as
** described above, or until [sqlite3_step()] or [sqlite3_reset()] or
** [sqlite3_finalize()] is called.  ^The memory space used to hold strings
** and BLOBs is freed automatically.  Do <em>not</em> pass the pointers returned
** from [sqlite3_column_blob()], [sqlite3_column_text()], etc. into
** [sqlite3_free()].
**
** ^(If a memory allocation error occurs during the evaluation of any
** of these routines, a default value is returned.  The default value
** is either the integer 0, the floating point number 0.0, or a NULL
** pointer.  Subsequent calls to [sqlite3_errcode()] will return
** [SQLITE_NOMEM].)^
*/
const void *sqlite3_column_blob(sqlite3_stmt*, int iCol);
int sqlite3_column_bytes(sqlite3_stmt*, int iCol);
int sqlite3_column_bytes16(sqlite3_stmt*, int iCol);
double sqlite3_column_double(sqlite3_stmt*, int iCol);
int sqlite3_column_int(sqlite3_stmt*, int iCol);
sqlite3_int64 sqlite3_column_int64(sqlite3_stmt*, int iCol);
const unsigned char *sqlite3_column_text(sqlite3_stmt*, int iCol);
const void *sqlite3_column_text16(sqlite3_stmt*, int iCol);

int sqlite3_column_type(sqlite3_stmt*, int iCol);

sqlite3_value *sqlite3_column_value(sqlite3_stmt*, int iCol);

/*
** CAPI3REF: Destroy A Prepared Statement Object
** DESTRUCTOR: sqlite3_stmt
**
** ^The sqlite3_finalize() function is called to delete a [prepared statement].
** ^If the most recent evaluation of the statement encountered no errors
................................................................................
                      void*,sqlite3_int64);
#endif

/*
** CAPI3REF: Obtaining SQL Values
** METHOD: sqlite3_value
**
** The C-language implementation of SQL functions and aggregates uses
** this set of interface routines to access the parameter values on
** the function or aggregate.  



















**
** The xFunc (for scalar functions) or xStep (for aggregates) parameters
** to [sqlite3_create_function()] and [sqlite3_create_function16()]
** define callbacks that implement the SQL functions and aggregates.
** The 3rd parameter to these callbacks is an array of pointers to



** [protected sqlite3_value] objects.  There is one [sqlite3_value] object for
** each parameter to the SQL function.  These routines are used to
** extract values from the [sqlite3_value] objects.


**
** These routines work only with [protected sqlite3_value] objects.
** Any attempt to use these routines on an [unprotected sqlite3_value]
** object results in undefined behavior.
**
** ^These routines work just like the corresponding [column access functions]
** except that these routines take a single [protected sqlite3_value] object
** pointer instead of a [sqlite3_stmt*] pointer and an integer column number.
**
** ^The sqlite3_value_text16() interface extracts a UTF-16 string
** in the native byte-order of the host machine.  ^The
................................................................................
** [sqlite3_value_bytes()], [sqlite3_value_bytes16()], [sqlite3_value_text()],
** or [sqlite3_value_text16()].
**
** These routines must be called from the same thread as
** the SQL function that supplied the [sqlite3_value*] parameters.
*/
const void *sqlite3_value_blob(sqlite3_value*);
int sqlite3_value_bytes(sqlite3_value*);
int sqlite3_value_bytes16(sqlite3_value*);
double sqlite3_value_double(sqlite3_value*);
int sqlite3_value_int(sqlite3_value*);
sqlite3_int64 sqlite3_value_int64(sqlite3_value*);
const unsigned char *sqlite3_value_text(sqlite3_value*);
const void *sqlite3_value_text16(sqlite3_value*);
const void *sqlite3_value_text16le(sqlite3_value*);
const void *sqlite3_value_text16be(sqlite3_value*);


int sqlite3_value_type(sqlite3_value*);
int sqlite3_value_numeric_type(sqlite3_value*);

/*
** CAPI3REF: Finding The Subtype Of SQL Values
** METHOD: sqlite3_value
**







>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>







 







>
>
>
>
>
>



|
|
|
|
>
>
>


>
>
>
>







 







>
>
>
>

<
>
|







 







|










<
<





>
|
>
|







 







|
|
|
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>

<
<
<
<
>
>
>
|
<
<
>
>



|







 







<
<







>
>







4263
4264
4265
4266
4267
4268
4269
4270
4271
4272
4273
4274
4275
4276
4277
4278
4279
4280
4281
4282
4283
4284
4285
4286
4287
4288
4289
4290
4291
4292
4293
4294
4295
4296
4297
4298
....
4307
4308
4309
4310
4311
4312
4313
4314
4315
4316
4317
4318
4319
4320
4321
4322
4323
4324
4325
4326
4327
4328
4329
4330
4331
4332
4333
4334
4335
4336
4337
4338
4339
4340
4341
4342
....
4366
4367
4368
4369
4370
4371
4372
4373
4374
4375
4376
4377

4378
4379
4380
4381
4382
4383
4384
4385
4386
....
4444
4445
4446
4447
4448
4449
4450
4451
4452
4453
4454
4455
4456
4457
4458
4459
4460
4461


4462
4463
4464
4465
4466
4467
4468
4469
4470
4471
4472
4473
4474
4475
4476
4477
....
4697
4698
4699
4700
4701
4702
4703
4704
4705
4706
4707
4708
4709
4710
4711
4712
4713
4714
4715
4716
4717
4718
4719
4720
4721
4722
4723
4724
4725
4726




4727
4728
4729
4730


4731
4732
4733
4734
4735
4736
4737
4738
4739
4740
4741
4742
4743
....
4769
4770
4771
4772
4773
4774
4775


4776
4777
4778
4779
4780
4781
4782
4783
4784
4785
4786
4787
4788
4789
4790
4791
#endif
#define SQLITE3_TEXT     3

/*
** CAPI3REF: Result Values From A Query
** KEYWORDS: {column access functions}
** METHOD: sqlite3_stmt
**
** <b>Summary:</b>
** <blockquote><table border=0 cellpadding=0 cellspacing=0>
** <tr><td><b>sqlite3_column_blob</b><td>&rarr;<td>BLOB result
** <tr><td><b>sqlite3_column_double</b><td>&rarr;<td>REAL result
** <tr><td><b>sqlite3_column_int</b><td>&rarr;<td>32-bit INTEGER result
** <tr><td><b>sqlite3_column_int64</b><td>&rarr;<td>64-bit INTEGER result
** <tr><td><b>sqlite3_column_text</b><td>&rarr;<td>UTF-8 TEXT result
** <tr><td><b>sqlite3_column_text16</b><td>&rarr;<td>UTF-16 TEXT result
** <tr><td><b>sqlite3_column_value</b><td>&rarr;<td>The result as an 
** [sqlite3_value|unprotected sqlite3_value] object.
** <tr><td>&nbsp;<td>&nbsp;<td>&nbsp;
** <tr><td><b>sqlite3_column_bytes</b><td>&rarr;<td>Size of a BLOB
** or a UTF-8 TEXT result in bytes
** <tr><td><b>sqlite3_column_bytes16&nbsp;&nbsp;</b>
** <td>&rarr;&nbsp;&nbsp;<td>Size of UTF-16
** TEXT in bytes
** <tr><td><b>sqlite3_column_type</b><td>&rarr;<td>Default
** datatype of the result
** </table></blockquote>
**
** <b>Details:</b>
**
** ^These routines return information about a single column of the current
** result row of a query.  ^In every case the first argument is a pointer
** to the [prepared statement] that is being evaluated (the [sqlite3_stmt*]
** that was returned from [sqlite3_prepare_v3()] or one of its variants)
** and the second argument is the index of the column for which information
** should be returned. ^The leftmost column of the result set has the index 0.
................................................................................
** If any of these routines are called after [sqlite3_reset()] or
** [sqlite3_finalize()] or after [sqlite3_step()] has returned
** something other than [SQLITE_ROW], the results are undefined.
** If [sqlite3_step()] or [sqlite3_reset()] or [sqlite3_finalize()]
** are called from a different thread while any of these routines
** are pending, then the results are undefined.
**
** The first six interfaces (_blob, _double, _int, _int64, _text, and _text16)
** each return the value of a result column in a specific data format.  If
** the result column is not initially in the requested format (for example,
** if the query returns an integer but the sqlite3_column_text() interface
** is used to extract the value) then an automatic type conversion is performed.
**
** ^The sqlite3_column_type() routine returns the
** [SQLITE_INTEGER | datatype code] for the initial data type
** of the result column.  ^The returned value is one of [SQLITE_INTEGER],
** [SQLITE_FLOAT], [SQLITE_TEXT], [SQLITE_BLOB], or [SQLITE_NULL].
** The return value of sqlite3_column_type() can be used to decide which
** of the first six interface should be used to extract the column value.
** The value returned by sqlite3_column_type() is only meaningful if no
** automatic type conversions have occurred for the value in question.  
** After a type conversion, the result of calling sqlite3_column_type()
** is undefined, though harmless.  Future
** versions of SQLite may change the behavior of sqlite3_column_type()
** following a type conversion.
**
** If the result is a BLOB or a TEXT string, then the sqlite3_column_bytes()
** or sqlite3_column_bytes16() interfaces can be used to determine the size
** of that BLOB or string.
**
** ^If the result is a BLOB or UTF-8 string then the sqlite3_column_bytes()
** routine returns the number of bytes in that BLOB or string.
** ^If the result is a UTF-16 string, then sqlite3_column_bytes() converts
** the string to UTF-8 and then returns the number of bytes.
** ^If the result is a numeric value then sqlite3_column_bytes() uses
** [sqlite3_snprintf()] to convert that value to a UTF-8 string and returns
................................................................................
** [unprotected sqlite3_value] object.  In a multithreaded environment,
** an unprotected sqlite3_value object may only be used safely with
** [sqlite3_bind_value()] and [sqlite3_result_value()].
** If the [unprotected sqlite3_value] object returned by
** [sqlite3_column_value()] is used in any other way, including calls
** to routines like [sqlite3_value_int()], [sqlite3_value_text()],
** or [sqlite3_value_bytes()], the behavior is not threadsafe.
** Hence, the sqlite3_column_value() interface
** is normally only useful within the implementation of 
** [application-defined SQL functions] or [virtual tables], not within
** top-level application code.
**

** The these routines may attempt to convert the datatype of the result.
** ^For example, if the internal representation is FLOAT and a text result
** is requested, [sqlite3_snprintf()] is used internally to perform the
** conversion automatically.  ^(The following table details the conversions
** that are applied:
**
** <blockquote>
** <table border="1">
** <tr><th> Internal<br>Type <th> Requested<br>Type <th>  Conversion
................................................................................
** to sqlite3_column_text() or sqlite3_column_blob() with calls to
** sqlite3_column_bytes16(), and do not mix calls to sqlite3_column_text16()
** with calls to sqlite3_column_bytes().
**
** ^The pointers returned are valid until a type conversion occurs as
** described above, or until [sqlite3_step()] or [sqlite3_reset()] or
** [sqlite3_finalize()] is called.  ^The memory space used to hold strings
** and BLOBs is freed automatically.  Do not pass the pointers returned
** from [sqlite3_column_blob()], [sqlite3_column_text()], etc. into
** [sqlite3_free()].
**
** ^(If a memory allocation error occurs during the evaluation of any
** of these routines, a default value is returned.  The default value
** is either the integer 0, the floating point number 0.0, or a NULL
** pointer.  Subsequent calls to [sqlite3_errcode()] will return
** [SQLITE_NOMEM].)^
*/
const void *sqlite3_column_blob(sqlite3_stmt*, int iCol);


double sqlite3_column_double(sqlite3_stmt*, int iCol);
int sqlite3_column_int(sqlite3_stmt*, int iCol);
sqlite3_int64 sqlite3_column_int64(sqlite3_stmt*, int iCol);
const unsigned char *sqlite3_column_text(sqlite3_stmt*, int iCol);
const void *sqlite3_column_text16(sqlite3_stmt*, int iCol);
sqlite3_value *sqlite3_column_value(sqlite3_stmt*, int iCol);
int sqlite3_column_bytes(sqlite3_stmt*, int iCol);
int sqlite3_column_bytes16(sqlite3_stmt*, int iCol);
int sqlite3_column_type(sqlite3_stmt*, int iCol);

/*
** CAPI3REF: Destroy A Prepared Statement Object
** DESTRUCTOR: sqlite3_stmt
**
** ^The sqlite3_finalize() function is called to delete a [prepared statement].
** ^If the most recent evaluation of the statement encountered no errors
................................................................................
                      void*,sqlite3_int64);
#endif

/*
** CAPI3REF: Obtaining SQL Values
** METHOD: sqlite3_value
**
** <b>Summary:</b>
** <blockquote><table border=0 cellpadding=0 cellspacing=0>
** <tr><td><b>sqlite3_value_blob</b><td>&rarr;<td>BLOB value
** <tr><td><b>sqlite3_value_double</b><td>&rarr;<td>REAL value
** <tr><td><b>sqlite3_value_int</b><td>&rarr;<td>32-bit INTEGER value
** <tr><td><b>sqlite3_value_int64</b><td>&rarr;<td>64-bit INTEGER value
** <tr><td><b>sqlite3_value_text</b><td>&rarr;<td>UTF-8 TEXT value
** <tr><td><b>sqlite3_value_text16</b><td>&rarr;<td>UTF-16 TEXT value in
** the native byteorder
** <tr><td><b>sqlite3_value_text16be</b><td>&rarr;<td>UTF-16be TEXT value
** <tr><td><b>sqlite3_value_text16le</b><td>&rarr;<td>UTF-16le TEXT value
** <tr><td>&nbsp;<td>&nbsp;<td>&nbsp;
** <tr><td><b>sqlite3_value_bytes</b><td>&rarr;<td>Size of a BLOB
** or a UTF-8 TEXT in bytes
** <tr><td><b>sqlite3_value_bytes16&nbsp;&nbsp;</b>
** <td>&rarr;&nbsp;&nbsp;<td>Size of UTF-16
** TEXT in bytes
** <tr><td><b>sqlite3_value_type</b><td>&rarr;<td>Default
** datatype of the value
** <tr><td><b>sqlite3_value_numeric_type&nbsp;&nbsp;</b>
** <td>&rarr;&nbsp;&nbsp;<td>Best numeric datatype of the value
** </table></blockquote>
**




** <b>Details:</b>
**
** This routine 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
** pointer instead of a [sqlite3_stmt*] pointer and an integer column number.
**
** ^The sqlite3_value_text16() interface extracts a UTF-16 string
** in the native byte-order of the host machine.  ^The
................................................................................
** [sqlite3_value_bytes()], [sqlite3_value_bytes16()], [sqlite3_value_text()],
** or [sqlite3_value_text16()].
**
** These routines must be called from the same thread as
** the SQL function that supplied the [sqlite3_value*] parameters.
*/
const void *sqlite3_value_blob(sqlite3_value*);


double sqlite3_value_double(sqlite3_value*);
int sqlite3_value_int(sqlite3_value*);
sqlite3_int64 sqlite3_value_int64(sqlite3_value*);
const unsigned char *sqlite3_value_text(sqlite3_value*);
const void *sqlite3_value_text16(sqlite3_value*);
const void *sqlite3_value_text16le(sqlite3_value*);
const void *sqlite3_value_text16be(sqlite3_value*);
int sqlite3_value_bytes(sqlite3_value*);
int sqlite3_value_bytes16(sqlite3_value*);
int sqlite3_value_type(sqlite3_value*);
int sqlite3_value_numeric_type(sqlite3_value*);

/*
** CAPI3REF: Finding The Subtype Of SQL Values
** METHOD: sqlite3_value
**