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https://issues.apache.org/jira/browse/DERBY-3907?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12664048#action_12664048
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kristwaa edited comment on DERBY-3907 at 1/15/09 1:01 AM:
-----------------------------------------------------------------
Committed patch 5a to trunk with revision 734630.
A quick comment on the following piece of code from
EmbedResultSet.getCharacterStream:
-----
CharacterStreamDescriptor csd = dvd.getStreamWithDescriptor();
if (csd == null) {
String val = dvd.getString();
if (lmfs > 0) {
if (val.length() > lmfs)
val = val.substring(0, lmfs);
}
java.io.Reader ret = new java.io.StringReader(val);
currentStream = ret;
return ret;
}
// See if we have to enforce a max field size.
if (lmfs > 0) {
csd = new CharacterStreamDescriptor.Builder().copyState(csd).
maxCharLength(lmfs).build();
}
java.io.Reader ret = new UTF8Reader(csd, this, syncLock);
-----
The last "if (lmfs > 0)" statement will never be run as long as
SQLChar.getStreamWithDescriptor() returns null, because then the value will be
materialized (SQLChar.getString()).
We can allow non-Clob values to be treated as streams as well, but I'm not sure
it is worth it due to the limited size (max 32700 chars).
Opinons?
was (Author: kristwaa):
Committed patch 5a to trunk with revision 734630.
A quick comment on the following piece of code from
EmbedResultSet.getCharacterStream:
-----
CharacterStreamDescriptor csd = dvd.getStreamWithDescriptor();
if (csd == null) {
String val = dvd.getString();
if (lmfs > 0) {
if (val.length() > lmfs)
val = val.substring(0, lmfs);
}
java.io.Reader ret = new
java.io.StringReader(val);
currentStream = ret;
return ret;
}
// See if we have to enforce a max field size.
if (lmfs > 0) {
csd = new CharacterStreamDescriptor.Builder().copyState(csd).
maxCharLength(lmfs).build();
}
java.io.Reader ret = new UTF8Reader(csd, this, syncLock);
-----
The last "if (lmfs < 0)" statement will never be run as long as
SQLChar.getStreamWithDescriptor() returns null, because then the value will be
materialized (SQLChar.getString()).
We can allow non-Clob values to be treated as streams as well, but I'm not sure
it is worth it due to the limited size (max 32700 chars).
Opinons?
> Save useful length information for Clobs in store
> -------------------------------------------------
>
> Key: DERBY-3907
> URL: https://issues.apache.org/jira/browse/DERBY-3907
> Project: Derby
> Issue Type: Improvement
> Components: JDBC, Store
> Affects Versions: 10.5.0.0
> Reporter: Kristian Waagan
> Assignee: Kristian Waagan
> Fix For: 10.5.0.0
>
> Attachments: derby-3907-1a-alternative_approach.diff,
> derby-3907-2b-header_write_preparation.diff,
> derby-3907-2b-header_write_preparation.diff,
> derby-3907-2b-header_write_preparation.stat,
> derby-3907-2c-header_write_preparation-PREVIEW.diff,
> derby-3907-2c-header_write_preparation-PREVIEW.stat,
> derby-3907-2c-header_write_preparation.diff,
> derby-3907-2c-header_write_preparation.diff,
> derby-3907-2c-header_write_preparation.stat,
> derby-3907-3a-readertoutf8stream_cleanup.diff,
> derby-3907-3a-readertoutf8stream_cleanup.diff,
> derby-3907-3a-readertoutf8stream_cleanup.stat,
> derby-3907-3b-readertoutf8stream_cleanup.diff,
> derby-3907-4a-add_getStreamWithDescriptor.diff,
> derby-3907-4a-add_getStreamWithDescriptor.stat,
> derby-3907-5a-use_getStreamWithDescriptor.diff,
> derby-3907-5a-use_getStreamWithDescriptor.stat
>
>
> The store should save useful length information for Clobs. This allows the
> length to be found without decoding the whole data stream.
> The following thread raised the issue on what information to store, and also
> contains some background information:
> http://www.nabble.com/Storing-length-information-for-CLOB-on-disk-tp19197535p19197535.html
> The information to store, and the exact format of it, is still to be
> discussed/determined.
> Currently two bytes are set aside for length information, which is inadequate.
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