** must be unique and what to do if they are not.  When Index.onError=OE_None,
** it means this is not a unique index.  Otherwise it is a unique index
** and the value of Index.onError indicate the which conflict resolution 
** algorithm to employ whenever an attempt is made to insert a non-unique
** element.
*/
struct Index {
  char *zName;     /* Name of this index */
  int *aiColumn;   /* Which columns are used by this index.  1st is 0 */
  tRowcnt *aiRowEst; /* Result of ANALYZE: Est. rows selected by each column */
  Table *pTable;   /* The SQL table being indexed */
  char *zColAff;   /* String defining the affinity of each column */
  Index *pNext;    /* The next index associated with the same table */
  Schema *pSchema; /* Schema containing this index */
  u8 *aSortOrder;  /* Array of size Index.nColumn. True==DESC, False==ASC */
  char **azColl;   /* Array of collation sequence names for index */
  int nColumn;     /* Number of columns in the table used by this index */
  int tnum;        /* Page containing root of this index in database file */

  u8 onError;      /* OE_Abort, OE_Ignore, OE_Replace, or OE_None */
  u8 autoIndex;    /* True if is automatically created (ex: by UNIQUE) */
  u8 bUnordered;   /* Use this index for == or IN queries only */
#ifdef SQLITE_ENABLE_STAT3
  int nSample;             /* Number of elements in aSample[] */
  tRowcnt avgEq;           /* Average nEq value for key values not in aSample */
  IndexSample *aSample;    /* Samples of the left-most key */
#endif
};

** must be unique and what to do if they are not.  When Index.onError=OE_None,
** it means this is not a unique index.  Otherwise it is a unique index
** and the value of Index.onError indicate the which conflict resolution 
** algorithm to employ whenever an attempt is made to insert a non-unique
** element.
*/
struct Index {
  char *zName;             /* Name of this index */
  int *aiColumn;           /* Which columns are used by this index.  1st is 0 */
  tRowcnt *aiRowEst;       /* From ANALYZE: Est. rows selected by each column */
  Table *pTable;           /* The SQL table being indexed */
  char *zColAff;           /* String defining the affinity of each column */
  Index *pNext;            /* The next index associated with the same table */
  Schema *pSchema;         /* Schema containing this index */
  u8 *aSortOrder;          /* for each column: True==DESC, False==ASC */
  char **azColl;           /* Array of collation sequence names for index */

  int tnum;                /* DB Page containing root of this index */
  u16 nColumn;             /* Number of columns in table used by this index */
  u8 onError;              /* OE_Abort, OE_Ignore, OE_Replace, or OE_None */
  unsigned autoIndex:2;    /* 1==UNIQUE, 2==PRIMARY KEY, 0==CREATE INDEX */
  unsigned bUnordered:1;   /* Use this index for == or IN queries only */
#ifdef SQLITE_ENABLE_STAT3
  int nSample;             /* Number of elements in aSample[] */
  tRowcnt avgEq;           /* Average nEq value for key values not in aSample */
  IndexSample *aSample;    /* Samples of the left-most key */
#endif
};