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Overview
Comment:Updates to the requirements on the sqlite3_create_function() family of interfaces.
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SHA1: f03c608993d1c37b45ba8e0a6a4e941bdcb57ffa
User & Date: drh 2010-09-16 19:49:22
Context
2010-09-16
23:18
Fix a comment typo in memjournal.c check-in: 9b272ed4 user: drh tags: trunk
19:49
Updates to the requirements on the sqlite3_create_function() family of interfaces. check-in: f03c6089 user: drh tags: trunk
18:51
Add tests for ORDER BY, LIMIT and OFFSET clauses to e_select.test. check-in: 7c989db5 user: dan tags: trunk
Changes
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Changes to src/callback.c.

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  /* If no match is found, search the built-in functions.
  **
  ** If the SQLITE_PreferBuiltin flag is set, then search the built-in
  ** functions even if a prior app-defined function was found.  And give
  ** priority to built-in functions.
  **
  ** Except, if createFlag is true, that means that we are trying to
  ** install a new function.  Whatever FuncDef structure is returned will
  ** have fields overwritten with new information appropriate for the
  ** new function.  But the FuncDefs for built-in functions are read-only.
  ** So we must not search for built-ins when creating a new function.
  */ 
  if( !createFlag && (pBest==0 || (db->flags & SQLITE_PreferBuiltin)!=0) ){
    FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite3GlobalFunctions);
    bestScore = 0;







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  /* If no match is found, search the built-in functions.
  **
  ** If the SQLITE_PreferBuiltin flag is set, then search the built-in
  ** functions even if a prior app-defined function was found.  And give
  ** priority to built-in functions.
  **
  ** Except, if createFlag is true, that means that we are trying to
  ** install a new function.  Whatever FuncDef structure is returned it will
  ** have fields overwritten with new information appropriate for the
  ** new function.  But the FuncDefs for built-in functions are read-only.
  ** So we must not search for built-ins when creating a new function.
  */ 
  if( !createFlag && (pBest==0 || (db->flags & SQLITE_PreferBuiltin)!=0) ){
    FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite3GlobalFunctions);
    bestScore = 0;

Changes to src/sqlite.h.in.

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** aggregate may take any number of arguments between 0 and the limit
** set by [sqlite3_limit]([SQLITE_LIMIT_FUNCTION_ARG]).  If the third
** parameter is less than -1 or greater than 127 then the behavior is
** undefined.
**
** ^The fourth parameter, eTextRep, specifies what
** [SQLITE_UTF8 | text encoding] this SQL function prefers for
** its parameters.  Any SQL function implementation should be able to work
** work with UTF-8, UTF-16le, or UTF-16be.  But some implementations may be
** more efficient with one encoding than another.  ^An application may
** invoke sqlite3_create_function() or sqlite3_create_function16() multiple
** times with the same function but with different values of eTextRep.
** ^When multiple implementations of the same function are available, SQLite
** will pick the one that involves the least amount of data conversion.
** If there is only a single implementation which does not care what text
** encoding is used, then the fourth argument should be [SQLITE_ANY].
................................................................................
** pointers to C-language functions that implement the SQL function or
** aggregate. ^A scalar SQL function requires an implementation of the xFunc
** callback only; NULL pointers must be passed as the xStep and xFinal
** parameters. ^An aggregate SQL function requires an implementation of xStep
** and xFinal and NULL pointer must be passed for xFunc. ^To delete an existing
** SQL function or aggregate, pass NULL poiners for all three function
** callbacks.







**
** ^It is permitted to register multiple implementations of the same
** functions with the same name but with either differing numbers of
** arguments or differing preferred text encodings.  ^SQLite will use
** the implementation that most closely matches the way in which the
** SQL function is used.  ^A function implementation with a non-negative
** nArg parameter is a better match than a function implementation with
................................................................................
** matches the database encoding is a better
** match than a function where the encoding is different.  
** ^A function where the encoding difference is between UTF16le and UTF16be
** is a closer match than a function where the encoding difference is
** between UTF8 and UTF16.
**
** ^Built-in functions may be overloaded by new application-defined functions.
** ^The first application-defined function with a given name overrides all
** built-in functions in the same [database connection] with the same name.
** ^Subsequent application-defined functions of the same name only override 
** prior application-defined functions that are an exact match for the
** number of parameters and preferred encoding.
**
** ^An application-defined function is permitted to call other
** SQLite interfaces.  However, such calls must not
** close the database connection nor finalize or reset the prepared
** statement in which the function is running.
*/
int sqlite3_create_function(







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** aggregate may take any number of arguments between 0 and the limit
** set by [sqlite3_limit]([SQLITE_LIMIT_FUNCTION_ARG]).  If the third
** parameter is less than -1 or greater than 127 then the behavior is
** undefined.
**
** ^The fourth parameter, eTextRep, specifies what
** [SQLITE_UTF8 | text encoding] this SQL function prefers for
** its parameters.  Every SQL function implementation must be able to work
** with UTF-8, UTF-16le, or UTF-16be.  But some implementations may be
** more efficient with one encoding than another.  ^An application may
** invoke sqlite3_create_function() or sqlite3_create_function16() multiple
** times with the same function but with different values of eTextRep.
** ^When multiple implementations of the same function are available, SQLite
** will pick the one that involves the least amount of data conversion.
** If there is only a single implementation which does not care what text
** encoding is used, then the fourth argument should be [SQLITE_ANY].
................................................................................
** pointers to C-language functions that implement the SQL function or
** aggregate. ^A scalar SQL function requires an implementation of the xFunc
** callback only; NULL pointers must be passed as the xStep and xFinal
** parameters. ^An aggregate SQL function requires an implementation of xStep
** and xFinal and NULL pointer must be passed for xFunc. ^To delete an existing
** SQL function or aggregate, pass NULL poiners for all three function
** callbacks.
**
** ^If the tenth parameter to sqlite3_create_function_v2() is not NULL,
** then it is invoked when the function is deleted, either by being
** overloaded or when the database connection closes.
** ^When the destructure callback of the tenth parameter is invoked, it
** is passed a single argument which is a copy of the pointer which was
** the fifth parameter to sqlite3_create_function_v2().
**
** ^It is permitted to register multiple implementations of the same
** functions with the same name but with either differing numbers of
** arguments or differing preferred text encodings.  ^SQLite will use
** the implementation that most closely matches the way in which the
** SQL function is used.  ^A function implementation with a non-negative
** nArg parameter is a better match than a function implementation with
................................................................................
** matches the database encoding is a better
** match than a function where the encoding is different.  
** ^A function where the encoding difference is between UTF16le and UTF16be
** is a closer match than a function where the encoding difference is
** between UTF8 and UTF16.
**
** ^Built-in functions may be overloaded by new application-defined functions.





**
** ^An application-defined function is permitted to call other
** SQLite interfaces.  However, such calls must not
** close the database connection nor finalize or reset the prepared
** statement in which the function is running.
*/
int sqlite3_create_function(