[Roy B, please keep your tongue in your cheek ;-), I know there's a better
way: steer completely clear of btrees! But they're a feature, so I'm trying
to use that (since it's already in use and sometimes works nicely.]
Can some Image internals person (Stan 'wrote the code but doesn't use it' ?)
please take a look? It's not THAT involved...
MasterSet DetailSet Search Sort (supr-style FORM
SETS)
ACT-TYPES(indexed) ACT-CODES ACT-TYPE (x2) ACT-CODE (x6)
DetailSet Search Sort MasterSet
ACT-CODES !ACT-TYPE ACT-CODE ACT-TYPES(indexed)
ACT-CODE ACT-CODE-AUTO
more detail: the master set contains
01, 02, 04, 05, 06, etc, ... 27 of them. they're linked to the detail via
act-type of course (x2); the detail set contains ACT-TYPE(x2)ACT-CODE(x6),
specifically
0101001 , 0101002 , 0101003 , ... 0202001 , 0202002 , ... 0202999 , 0404001
, ...
record0 , record1 , record2 , ... record19, record20, ... record47,
record48, ...
----------------------------------------------------------------------------
------
Having sorted and reloaded the detail set for ease of debug, I'm basically
doing
MOVE 1 TO IMAGE-MODE
MOVE 'ACT-CODES' TO IMAGE-SET
MOVE 'ACT-TYPE' TO IMAGE-SEARCH
MOVE '@' TO IMAGE-ARG
PERFORM DBFIND (returns status=0, 1182 recs, last=1182, 1st=0, all perfect.)
MOVE 5 TO IMAGE-MODE
PERFORM DBGET (returns status=0, rec=0, prev=0, next=1)
PERFORM UNTIL NOT DB-OK
MOVE IMAGE-BUFFER TO ACT-CODES-BUFFER
IF ACT-CODE ( 1 : 2 ) <> PREV-TYPE
MOVE ACT-CODE ( 1 : 2 ) TO IMAGE-ARG
MOVE 7 TO IMAGE-MODE
MOVE ACT-TYPES TO IMAGE-SET
PERFORM DBGET (returns just fine)
display the heading
MOVE ACT-TYPE TO PREV-TYPE
END-IF
display the detail record *2
MOVE 5 TO IMAGE-MODE
MOVE 'ACT-CODES' TO IMAGE-SET
PERFORM DBGET (returns status=0, rec=1, prev=0, next=2, all perfect.)
END-PERFORM
GOBACK
this works just great, but I notice that every time I get to a break in
ACT-CODE ( 1 : 2 ) (a switch in the contents of ACT-TYPE), then DBGET(5)
returns next=0. As long as I do no further messing around, the superchain
remains intact, and though there are several ACT-TYPE groups and I see
next=0 several times, the program runs to completion, reporting all 1182
ACT-CODES records and does the heading break 22 times, once for each
ACT-TYPES record. Lovely, isn't it?
QUESTION 1: can anybody explain the seemingly anomalous next=0 at the DBGET
breakpoints? this occurs whether or not I go after the appropriate header
record or not, and coincides with switches to the next real entry in the
master set aka 'chink in the chain'. And yes, the program works, so far.
QUESTION 2: I'm trying to enhance the program by adding a subpgm call at
"*2". That subpgm will do some goofing around in the same detail set, so
I've carefully added 'typical' save-my-place code: After each
DBGET(5,ACT-CODES) I save IMAGE-RECORD-NUMBER, and before the next
DBGET(5,ACT-CODES), I do
MOVE 1 TO IMAGE-MODE
MOVE 'ACT-CODES' TO IMAGE-SET
MOVE 'ACT-TYPE' TO IMAGE-SEARCH
MOVE '@' TO IMAGE-ARG
PERFORM DBFIND
which re-establishes the same superchain, including all 1182 records; then I
do
MOVE SAVE-RECORD-NUMBER TO IMAGE-ARGUMENT-I2
MOVE 4 TO IMAGE-MODE
MOVE 'ACT-CODES' TO IMAGE-SET
PERFORM DBGET (which really does get back the previous record, and
which would ordinarily (ie no btrees) re-establish my exact position on the
chain. But the subsequent DBGET mode 5 returns record 19, not record 48;
that produces a loop. Note the subprogram is not there yet, just the
save-my-place code.
Also note that record 19 is the first record on the 2nd real chain, and that
record 48 is the first record on the 3rd real chain. obviously something vs
btrees, but what?
TIA
Tracy Pierce
415-923-2266
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