Function idxPopulateStat1

lib-src/sqlite/shell.c:10017–10111

** This function is called as part of sqlite3_expert_analyze(). Candidate ** indexes have already been created in database sqlite3expert.dbm, this ** function populates sqlite_stat1 table in the same database. ** ** The stat1 data is generated by querying the */

** The stat1 data is generated by querying the 
*/
static int idxPopulateStat1(sqlite3expert *p, char **pzErr){
  int rc = SQLITE_OK;
  int nMax =0;
  struct IdxRemCtx *pCtx = 0;
  struct IdxSampleCtx samplectx; 
  int i;
  i64 iPrev = -100000;
  sqlite3_stmt *pAllIndex = 0;
  sqlite3_stmt *pIndexXInfo = 0;
  sqlite3_stmt *pWrite = 0;

  const char *zAllIndex =
    "SELECT s.rowid, s.name, l.name FROM "
    "  sqlite_schema AS s, "
    "  pragma_index_list(s.name) AS l "
    "WHERE s.type = 'table'";
  const char *zIndexXInfo = 
    "SELECT name, coll FROM pragma_index_xinfo(?) WHERE key";
  const char *zWrite = "INSERT INTO sqlite_stat1 VALUES(?, ?, ?)";

  /* If iSample==0, no sqlite_stat1 data is required. */
  if( p->iSample==0 ) return SQLITE_OK;

  rc = idxLargestIndex(p->dbm, &nMax, pzErr);
  if( nMax<=0 || rc!=SQLITE_OK ) return rc;

  rc = sqlite3_exec(p->dbm, "ANALYZE; PRAGMA writable_schema=1", 0, 0, 0);

  if( rc==SQLITE_OK ){
    int nByte = sizeof(struct IdxRemCtx) + (sizeof(struct IdxRemSlot) * nMax);
    pCtx = (struct IdxRemCtx*)idxMalloc(&rc, nByte);
  }

  if( rc==SQLITE_OK ){
    sqlite3 *dbrem = (p->iSample==100 ? p->db : p->dbv);
    rc = sqlite3_create_function(
        dbrem, "rem", 2, SQLITE_UTF8, (void*)pCtx, idxRemFunc, 0, 0
    );
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3_create_function(
        p->db, "sample", 0, SQLITE_UTF8, (void*)&samplectx, idxSampleFunc, 0, 0
    );
  }

  if( rc==SQLITE_OK ){
    pCtx->nSlot = nMax+1;
    rc = idxPrepareStmt(p->dbm, &pAllIndex, pzErr, zAllIndex);
  }
  if( rc==SQLITE_OK ){
    rc = idxPrepareStmt(p->dbm, &pIndexXInfo, pzErr, zIndexXInfo);
  }
  if( rc==SQLITE_OK ){
    rc = idxPrepareStmt(p->dbm, &pWrite, pzErr, zWrite);
  }

  while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pAllIndex) ){
    i64 iRowid = sqlite3_column_int64(pAllIndex, 0);