SQLite

  sqlite3 *db = pParse->db;
  u8 enc = ENC(db);
  u8 initbusy = db->init.busy;
  CollSeq *pColl;

  pColl = sqlite3FindCollSeq(db, enc, zName, initbusy);
  if( !initbusy && (!pColl || !pColl->xCmp) ){
    pColl = sqlite3GetCollSeq(db, enc, pColl, zName);
    if( !pColl ){
      sqlite3ErrorMsg(pParse, "no such collation sequence: %s", zName);
    }
  }

  return pColl;
}

** $Id: callback.c,v 1.42 2009/06/17 00:35:31 drh Exp $
*/

#include "sqliteInt.h"

/*
** Invoke the 'collation needed' callback to request a collation sequence
** in the encoding enc of name zName, length nName.

*/
static void callCollNeeded(sqlite3 *db, int enc, const char *zName){
  assert( !db->xCollNeeded || !db->xCollNeeded16 );
  if( db->xCollNeeded ){
    char *zExternal = sqlite3DbStrDup(db, zName);
    if( !zExternal ) return;
    db->xCollNeeded(db->pCollNeededArg, db, enc, zExternal);
    sqlite3DbFree(db, zExternal);
  }
#ifndef SQLITE_OMIT_UTF16
  if( db->xCollNeeded16 ){
    char const *zExternal;
    sqlite3_value *pTmp = sqlite3ValueNew(db);
    sqlite3ValueSetStr(pTmp, -1, zName, SQLITE_UTF8, SQLITE_STATIC);

  }
  return SQLITE_ERROR;
}

/*
** This function is responsible for invoking the collation factory callback
** or substituting a collation sequence of a different encoding when the
** requested collation sequence is not available in the desired encoding.

** 
** If it is not NULL, then pColl must point to the database native encoding 
** collation sequence with name zName, length nName.
**
** The return value is either the collation sequence to be used in database
** db for collation type name zName, length nName, or NULL, if no collation
** sequence can be found.
**
** See also: sqlite3LocateCollSeq(), sqlite3FindCollSeq()
*/
CollSeq *sqlite3GetCollSeq(
  sqlite3* db,          /* The database connection */
  int enc,              /* The desired encoding for the collating sequence */
  CollSeq *pColl,       /* Collating sequence with native encoding, or NULL */
  const char *zName     /* Collating sequence name */
){
  CollSeq *p;

  p = pColl;
  if( !p ){
    p = sqlite3FindCollSeq(db, enc, zName, 0);
  }
  if( !p || !p->xCmp ){
    /* No collation sequence of this type for this encoding is registered.
    ** Call the collation factory to see if it can supply us with one.
    */
    callCollNeeded(db, enc, zName);
    p = sqlite3FindCollSeq(db, enc, zName, 0);
  }
  if( p && !p->xCmp && synthCollSeq(db, p) ){
    p = 0;
  }
  assert( !p || p->xCmp );
  return p;
}

** request a definition of the collating sequence. If this doesn't work, 
** an equivalent collating sequence that uses a text encoding different
** from the main database is substituted, if one is available.
*/
int sqlite3CheckCollSeq(Parse *pParse, CollSeq *pColl){
  if( pColl ){
    const char *zName = pColl->zName;
    sqlite3 *db = pParse->db;
    CollSeq *p = sqlite3GetCollSeq(db, ENC(db), pColl, zName);
    if( !p ){
      sqlite3ErrorMsg(pParse, "no such collation sequence: %s", zName);
      pParse->nErr++;
      return SQLITE_ERROR;
    }
    assert( p==pColl );
  }

void sqlite3SelectPrep(Parse*, Select*, NameContext*);
int sqlite3ResolveExprNames(NameContext*, Expr*);
void sqlite3ResolveSelectNames(Parse*, Select*, NameContext*);
int sqlite3ResolveOrderGroupBy(Parse*, Select*, ExprList*, const char*);
void sqlite3ColumnDefault(Vdbe *, Table *, int, int);
void sqlite3AlterFinishAddColumn(Parse *, Token *);
void sqlite3AlterBeginAddColumn(Parse *, SrcList *);
CollSeq *sqlite3GetCollSeq(sqlite3*, int, CollSeq *, const char*);
char sqlite3AffinityType(const char*);
void sqlite3Analyze(Parse*, Token*, Token*);
int sqlite3InvokeBusyHandler(BusyHandler*);
int sqlite3FindDb(sqlite3*, Token*);
int sqlite3FindDbName(sqlite3 *, const char *);
int sqlite3AnalysisLoad(sqlite3*,int iDB);
void sqlite3DeleteIndexSamples(Index*);

      const u8 *z;
      int n;
      if( eType==SQLITE_BLOB ){
        z = (const u8 *)sqlite3_value_blob(pVal);
        pColl = db->pDfltColl;
        assert( pColl->enc==SQLITE_UTF8 );
      }else{
        pColl = sqlite3GetCollSeq(db, SQLITE_UTF8, 0, *pIdx->azColl);
        if( pColl==0 ){
          sqlite3ErrorMsg(pParse, "no such collation sequence: %s",
                          *pIdx->azColl);
          return SQLITE_ERROR;
        }
        z = (const u8 *)sqlite3ValueText(pVal, pColl->enc);
        if( !z ){
          return SQLITE_NOMEM;
        }
        assert( z && pColl && pColl->xCmp );