TurboIMAGE/XL Database Management System Reference Manual MPE/iX V6.5 (30391-90011)

Chapter 11 503
B-Tree Indices
External Commands and Utilities Affected
NOTE The length of the argument may not exceed the item length.
DBFIND Arguments
There are two distinct argument styles. The simple argument of the basic DBFIND mode 1
argument is generally interpreted as a sequence of bytes, perhaps containing a wildcard
character.
Another argument style, the structured argument, has been defined for DBFIND modes 4
and 24. This structure allows ranges of item values to be requested, and is explained
below.
DBFIND Structured Argument
The structure of the structured argument for DBFIND modes 4 and 24:
Bytes Meaning
1-2 Type of generic search. An ASCII character pair is in this field:
= search for key values equal to argument1
< search for key values less than argument1
<= search for key values less than or equal to argument1
> search for key values greater than argument1
>= search for key values greater than or equal to argument1
[ ] search for key values greater than or equal to argument1
AND less than or equal to argument2
c. The chain count is the sum of all chain counts (that is, the number of entries in the
super-chain for a B-Tree DBFIND). Record number for the last entry is obtained from the
last entry in the last chain. For first entry, record number of the first entry in the first
chain is obtained. For masters, the chain count reflects the total numberof master entries
qualified, and last entry and first entry values are zeroes.
d. When doing a B-Tree index search, mode-1-style argument is scanned to find the first
occurrence of the wildcard character in the argument text. If the wildcard is not found, a
non-B-Tree index search is done. If the wildcard is found, the rest of the argument text is
ignored. When not doing a B-Tree search (mode is 1 and BTREEMODE1 is OFF, or mode is
10), the entire argument, including any wildcard characters, will be treated as the actual
argument is for a DBFIND mode 1 in releases prior to the release with B-tree index
feature.
e. See "DBFIND Structured Argument" description later in this chapter.
f. For items that are text types (X, U), a B-Tree index search is done if the wildcard is
present in the argument. If the key item is a non-ASCII item, then a B-Tree index find is
not done, and a non-B-Tree index find (mode 1 with BTREEMODE1 is OFF) is done instead.
A programmer can do a B-Tree index find with non-ASCII items by explicitly using
DBFIND modes 4 or 24. (See "DBFIND mode 1-style and non-ASCII keys" below.) This mode
is similar to current TPI mode 21.
g. For detail data set, the halfwords 5-6, 7-8, and 9-10 have 2
31
−1. For master data set, the
halfword 5-6 has 2
31
−1 and 7-8 and 9-10 have zeroes.