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Overview
Comment:Revised documentation for sqlite3_limit(). Added some evidence marks and assert() statements to verify sqlite3_limit() behavior.
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SHA1: 883b9b7441593200def05d8a482bc92d3dc0e96b
User & Date: drh 2010-09-07 14:59:16
Context
2010-09-07
19:05
Add tests to e_select.test. check-in: 282dae7e user: dan tags: trunk
14:59
Revised documentation for sqlite3_limit(). Added some evidence marks and assert() statements to verify sqlite3_limit() behavior. check-in: 883b9b74 user: drh tags: trunk
14:12
Example icon file (32x32x4) for new logo. check-in: bd700794 user: shaneh tags: trunk
Changes
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Changes to src/main.c.

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**
** A new lower limit does not shrink existing constructs.
** It merely prevents new constructs that exceed the limit
** from forming.
*/
int sqlite3_limit(sqlite3 *db, int limitId, int newLimit){
  int oldLimit;






















  if( limitId<0 || limitId>=SQLITE_N_LIMIT ){
    return -1;
  }
  oldLimit = db->aLimit[limitId];
  if( newLimit>=0 ){
    if( newLimit>aHardLimit[limitId] ){
      newLimit = aHardLimit[limitId];
    }
    db->aLimit[limitId] = newLimit;
  }
  return oldLimit;
}

/*
** This routine does the work of opening a database on behalf of
** sqlite3_open() and sqlite3_open16(). The database filename "zFilename"  
** is UTF-8 encoded.
*/







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**
** A new lower limit does not shrink existing constructs.
** It merely prevents new constructs that exceed the limit
** from forming.
*/
int sqlite3_limit(sqlite3 *db, int limitId, int newLimit){
  int oldLimit;


  /* EVIDENCE-OF: R-30189-54097 For each limit category SQLITE_LIMIT_NAME
  ** there is a hard upper bound set at compile-time by a C preprocessor
  ** macro called SQLITE_MAX_NAME. (The "_LIMIT_" in the name is changed to
  ** "_MAX_".)
  */
  assert( aHardLimit[SQLITE_LIMIT_LENGTH]==SQLITE_MAX_LENGTH );
  assert( aHardLimit[SQLITE_LIMIT_SQL_LENGTH]==SQLITE_MAX_SQL_LENGTH );
  assert( aHardLimit[SQLITE_LIMIT_COLUMN]==SQLITE_MAX_COLUMN );
  assert( aHardLimit[SQLITE_LIMIT_EXPR_DEPTH]==SQLITE_MAX_EXPR_DEPTH );
  assert( aHardLimit[SQLITE_LIMIT_COMPOUND_SELECT]==SQLITE_MAX_COMPOUND_SELECT);
  assert( aHardLimit[SQLITE_LIMIT_VDBE_OP]==SQLITE_MAX_VDBE_OP );
  assert( aHardLimit[SQLITE_LIMIT_FUNCTION_ARG]==SQLITE_MAX_FUNCTION_ARG );
  assert( aHardLimit[SQLITE_LIMIT_ATTACHED]==SQLITE_MAX_ATTACHED );
  assert( aHardLimit[SQLITE_LIMIT_LIKE_PATTERN_LENGTH]==
                                               SQLITE_MAX_LIKE_PATTERN_LENGTH );
  assert( aHardLimit[SQLITE_LIMIT_VARIABLE_NUMBER]==SQLITE_MAX_VARIABLE_NUMBER);
  assert( aHardLimit[SQLITE_LIMIT_TRIGGER_DEPTH]==SQLITE_MAX_TRIGGER_DEPTH );
  assert( SQLITE_LIMIT_TRIGGER_DEPTH==(SQLITE_N_LIMIT-1) );


  if( limitId<0 || limitId>=SQLITE_N_LIMIT ){
    return -1;
  }
  oldLimit = db->aLimit[limitId];
  if( newLimit>=0 ){                   /* IMP: R-52476-28732 */
    if( newLimit>aHardLimit[limitId] ){
      newLimit = aHardLimit[limitId];  /* IMP: R-51463-25634 */
    }
    db->aLimit[limitId] = newLimit;
  }
  return oldLimit;                     /* IMP: R-53341-35419 */
}

/*
** This routine does the work of opening a database on behalf of
** sqlite3_open() and sqlite3_open16(). The database filename "zFilename"  
** is UTF-8 encoded.
*/

Changes to src/sqlite.h.in.

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** CAPI3REF: Run-time Limits
**
** ^(This interface allows the size of various constructs to be limited
** on a connection by connection basis.  The first parameter is the
** [database connection] whose limit is to be set or queried.  The
** second parameter is one of the [limit categories] that define a
** class of constructs to be size limited.  The third parameter is the
** new limit for that construct.  The function returns the old limit.)^
**
** ^If the new limit is a negative number, the limit is unchanged.
** ^(For the limit category of SQLITE_LIMIT_XYZ there is a 
** [limits | hard upper bound]
** set by a compile-time C preprocessor macro named 
** [limits | SQLITE_MAX_XYZ].
** (The "_LIMIT_" in the name is changed to "_MAX_".))^
** ^Attempts to increase a limit above its hard upper bound are
** silently truncated to the hard upper bound.
**





** Run-time limits are intended for use in applications that manage
** both their own internal database and also databases that are controlled
** by untrusted external sources.  An example application might be a
** web browser that has its own databases for storing history and
** separate databases controlled by JavaScript applications downloaded
** off the Internet.  The internal databases can be given the
** large, default limits.  Databases managed by external sources can
................................................................................
** These constants define various performance limits
** that can be lowered at run-time using [sqlite3_limit()].
** The synopsis of the meanings of the various limits is shown below.
** Additional information is available at [limits | Limits in SQLite].
**
** <dl>
** ^(<dt>SQLITE_LIMIT_LENGTH</dt>
** <dd>The maximum size of any string or BLOB or table row.<dd>)^
**
** ^(<dt>SQLITE_LIMIT_SQL_LENGTH</dt>
** <dd>The maximum length of an SQL statement, in bytes.</dd>)^
**
** ^(<dt>SQLITE_LIMIT_COLUMN</dt>
** <dd>The maximum number of columns in a table definition or in the
** result set of a [SELECT] or the maximum number of columns in an index
................................................................................
** <dd>The maximum number of [ATTACH | attached databases].)^</dd>
**
** ^(<dt>SQLITE_LIMIT_LIKE_PATTERN_LENGTH</dt>
** <dd>The maximum length of the pattern argument to the [LIKE] or
** [GLOB] operators.</dd>)^
**
** ^(<dt>SQLITE_LIMIT_VARIABLE_NUMBER</dt>
** <dd>The maximum number of variables in an SQL statement that can
** be bound.</dd>)^
**
** ^(<dt>SQLITE_LIMIT_TRIGGER_DEPTH</dt>
** <dd>The maximum depth of recursion for triggers.</dd>)^
** </dl>
*/
#define SQLITE_LIMIT_LENGTH                    0
#define SQLITE_LIMIT_SQL_LENGTH                1







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** CAPI3REF: Run-time Limits
**
** ^(This interface allows the size of various constructs to be limited
** on a connection by connection basis.  The first parameter is the
** [database connection] whose limit is to be set or queried.  The
** second parameter is one of the [limit categories] that define a
** class of constructs to be size limited.  The third parameter is the
** new limit for that construct.)^
**
** ^If the new limit is a negative number, the limit is unchanged.
** ^(For each limit category SQLITE_LIMIT_<i>NAME</i> there is a 
** [limits | hard upper bound]
** set at compile-time by a C preprocessor macro called
** [limits | SQLITE_MAX_<i>NAME</i>].
** (The "_LIMIT_" in the name is changed to "_MAX_".))^
** ^Attempts to increase a limit above its hard upper bound are
** silently truncated to the hard upper bound.
**
** ^Regardless of whether or not the limit was changed, the 
** [sqlite3_limit()] interface returns the prior value of the limit.
** ^Hence, to find the current value of a limit without changing it,
** simply invoke this interface with the third parameter set to -1.
**
** Run-time limits are intended for use in applications that manage
** both their own internal database and also databases that are controlled
** by untrusted external sources.  An example application might be a
** web browser that has its own databases for storing history and
** separate databases controlled by JavaScript applications downloaded
** off the Internet.  The internal databases can be given the
** large, default limits.  Databases managed by external sources can
................................................................................
** These constants define various performance limits
** that can be lowered at run-time using [sqlite3_limit()].
** The synopsis of the meanings of the various limits is shown below.
** Additional information is available at [limits | Limits in SQLite].
**
** <dl>
** ^(<dt>SQLITE_LIMIT_LENGTH</dt>
** <dd>The maximum size of any string or BLOB or table row, in bytes.<dd>)^
**
** ^(<dt>SQLITE_LIMIT_SQL_LENGTH</dt>
** <dd>The maximum length of an SQL statement, in bytes.</dd>)^
**
** ^(<dt>SQLITE_LIMIT_COLUMN</dt>
** <dd>The maximum number of columns in a table definition or in the
** result set of a [SELECT] or the maximum number of columns in an index
................................................................................
** <dd>The maximum number of [ATTACH | attached databases].)^</dd>
**
** ^(<dt>SQLITE_LIMIT_LIKE_PATTERN_LENGTH</dt>
** <dd>The maximum length of the pattern argument to the [LIKE] or
** [GLOB] operators.</dd>)^
**
** ^(<dt>SQLITE_LIMIT_VARIABLE_NUMBER</dt>
** <dd>The maximum index number of any [parameter] in an SQL statement.)^

**
** ^(<dt>SQLITE_LIMIT_TRIGGER_DEPTH</dt>
** <dd>The maximum depth of recursion for triggers.</dd>)^
** </dl>
*/
#define SQLITE_LIMIT_LENGTH                    0
#define SQLITE_LIMIT_SQL_LENGTH                1