I've been trying out Chris Collins code and I believe there may be a bug. So
here is my J session.
NB. =========================================================
NB. Start of J session
load 'data/jdb'
[ffd=: Open_jdb_ jpath '~temp'
+-+
|1|
+-+
Drop__ffd 'testdb'
[db=: Create__ffd 'testdb'
+-+
|2|
+-+
ht=: Create__db 'tblVarChar';0 : 0
field1 varchar
)
ht
+-+
|3|
+-+
NB. At this point, we know that my server locale is 1, my database locale is 2
and the table 'tblVarChar' is in locale 3.
NB. I'm going to insert a sequence of data and read the table immediately
Insert__db 'tblVarChar';'a'
Read__db 'from tblVarChar'
+------+---+
|field1|+-+|
| ||a||
| |+-+|
+------+---+
;:'bb ccc dddd eeeee ffffff'
+--+---+----+-----+------+
|bb|ccc|dddd|eeeee|ffffff|
+--+---+----+-----+------+
Insert__db 'tblVarChar';<<;:'bb ccc dddd eeeee ffffff'
Read__db 'from tblVarChar'
+------+----------------------------+
|field1|+-+--+---+----+-----+------+|
| ||a|bb|ccc|dddd|eeeee|ffffff||
| |+-+--+---+----+-----+------+|
+------+----------------------------+
NB. Up to this point, everything is going well, not I am going to force the JDB
Insert method to fail by inserting
NB. data in a format that it did not expect
Insert__db 'tblVarChar';<'zz'
|assertion failure: validate
| 1=#~.(#@".)&>'active';Tcolmap
Read__db 'from tblVarChar'
|index error: readbase1
| (rws{".)&.>cls
NB. End of J Session
NB. =========================================================
I believe that the data itself is not corrupted because the data can still be
seen there (note that 'zz' was saved)
c2__ht
+-+--+---+----+-----+------+--+
|a|bb|ccc|dddd|eeeee|ffffff|zz|
+-+--+---+----+-----+------+--+
>From what I remember from the discussions, JDB is transactional ... is there a
>way to rollback?
I feel that this should be considered a bug.
r/Alex
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of christopher collins
Sent: Thursday, December 17, 2009 2:12 PM
To: [email protected]
Subject: [Jprogramming] Newbie JDB problem: inserting chars in a 1 column char
table gives 'assertion failure'
Thanks to all for your help, especially Mr. Lam.
Your response, Mr. Lam, was very instructive.
I used your input to explore a bit more, with a couple of questions arising.
See the questions embedded below:
*****************************
load 'data/jdb'
ffd =: Open_jdb_ jpath , '~temp'
Drop__ffd 'testdb'
db =: Create__ffd 'testdb'
ht=: Create__db 'tblChar';0 : 0
c1 char
)
NB. JDB doc says a 'char' column is stored as a character matrix
NB. The next sentence works, even though it inserts a scalar, 'a'
NB. QUESTION: Is this contrary to the JDB doc?
Insert__db 'tblChar';'a'
]shape =. $'a'
NB. Inserts a list of shape 1
Insert__db 'tblChar';,'b'
]shape =. $ ,'b'
NB. Inserts a list of shape 3 1
Insert__db 'tblChar';,.'def'
]shape =. $ ,.'def'
NB. Inserts a list of shape 1 4
Insert__db 'tblChar';,:'ghih'
]shape =. $ ,:'ghih'
Insert__db 'tblChar';3 5 $'123457'
Insert__db 'tblChar';,:'012345678901234567890'
]shape=.$ ,:'012345678901234567890'
NB. A JDB 'char' column allows chars of varying lengths to be inserted
Insert__db 'tblChar';2 100$'1234567890'
Reads__db 'from tblChar'
NB. The insert below causes a failure
NB. After this the table can no longer be read.
NB. QUESTION: Is that behavior intended?
NB. If so, JDB seems a little fragile for the rough, unskilled hands
of newbies like me
NB. This insert, where '01' is a list of shape 2, fails even though an
insert of 'b', a list of shape 1 worked above.
NB. QUESTION: Is this behavior consistent in a way that I am not understanding?
Insert__db 'tblChar';'01'
Reads__db 'from tblChar'
Thanks again for the high quality help & instruction.
--chris--
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