Compact Index File Structure (.IDX)

See Also

Compact Index Header Record

Byte offset Description
00   03 Pointer to root node
04   07 Pointer to free node list ( -1 if not present)
08   11 Reserved for internal use
12   13 Length of key
14 Index options (any of the following numeric values or their sums):
1 a unique index
8 index has FOR clause
32 compact index format
64 compound index header
15 Index signature
16   19 Reserved for internal use
20   23 Reserved for internal use
24   27 Reserved for internal use
28   31 Reserved for internal use
32   35 Reserved for internal use
36   501 Reserved for internal use
502   503 Ascending or descending:
0 = ascending
1 = descending
504   505 Reserved for internal use
506   507 FOR expression pool length1
508   509 Reserved for internal use
510   511 Key expression pool length1
512   1023 Key expression pool (uncompiled)

1 This information tracks the space used in the key expression pool.

Compact Index Interior Node Record

Byte offset Description
00   01 Node attributes (any of the following numeric values or their sums):
a.0 index node
b.1 root node
c.2 leaf node
02   03 Number of keys present (0, 1 or many)
04   07 Pointer to node directly to left of current node (on same level, -1 if not present)
08   11 Pointer to node directly to right of current node (on same level; -1 if not present)
12   511 Up to 500 characters containing the key value for the length of the key with a four-byte hexadecimal number (stored in normal left-to-right format):

This node always contains the index key, record
number and intra-index pointer.2

The key/four-byte hexadecimal number combinations will occur the number of times indicated in bytes 02   03.


Compact Index Exterior Node Record

00   01 Node attributes (any of the following numeric values or their sums):
0 index node
1 root node
2 leaf node
02   03 Number of keys present (0, 1 or many)
04   07 Pointer to the node directly to the left of current node (on same level; -1 if not present)
08   11 Pointer to the node directly to right of the current node (on same level; -1 if not present)
12   13 Available free space in node
14   17 Record number mask
18 Duplicate byte count mask
19 Trailing byte count mask
20 Number of bits used for record number
21 Number of bits used for duplicate count
22 Number of bits used for trail count
23 Number of bytes holding record number, duplicate count and trailing count
24   511 Index keys and information2

2 Each entry consists of the record number, duplicate byte count and trailing byte count, all compacted. The key text is placed at the logical end of the node, working backwards, allowing for previous key entries.



Microsoft Visual FoxPro 6. 0 Programmer's Guide 1998
Microsoft Visual FoxPro 6. 0 Programmer's Guide 1998
ISBN: 1930919042
EAN: N/A
Year: 2004
Pages: 58

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