Name
LongReadLen (unsigned integer, inherited)
Synopsis
This attribute may be used to control the
maximum length of long fields (“blob,”
“memo,” etc.), which the driver will read from the
database automatically when it fetches each row of data. The
LongReadLen
attribute relates only to fetching and
reading long values; it is not involved in inserting or updating
them.
A value of 0
means not to automatically fetch any
long data. (fetch
should return
undef
for long fields when
LongReadLen
is 0
.)
The default is typically 0
(zero) bytes but may
vary between drivers. Applications fetching long fields should set
this value to slightly larger than the longest long field value to be
fetched.
Some databases return some long types encoded as pairs of hex digits.
For these types, LongReadLen
relates to the
underlying data length and not the doubled-up length of the encoded
string.
Changing the value of LongReadLen
for a statement
handle after it has been prepare
‘d will
typically have no effect, so it’s common to set
LongReadLen
on the $dbh
before
calling prepare
.
Note that the value used here has a direct effect on the memory used by the application, so don’t be too generous.
See LongTruncOk
for more information on truncation
behavior.
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