Re: Is Adding EOAttribute to EOEntity Thread Safe?
Re: Is Adding EOAttribute to EOEntity Thread Safe?
- Subject: Re: Is Adding EOAttribute to EOEntity Thread Safe?
- From: Chuck Hill <email@hidden>
- Date: Mon, 31 Mar 2008 12:39:17 -0700
That is how you lock the EOF stack. While the stack is locked, no
other thread can fetch / save. This same lock happens during all
fetch or save operations.
Chuck
On Mar 31, 2008, at 12:09 PM, Dov Rosenberg wrote:
Taking a look at the new code – I agree it looks a bit safer than
the old code. What is the implication for doing an EODatabaseContext
lock in a multi threaded app? Will that cause any problems if
multiple sessions are trying to do something similar concurrently?
Dov Rosenberg
On 3/30/08 5:56 PM, "Mike Schrag" <email@hidden> wrote:
It's not thread safe, and Wonder's implementation doesn't actually
work like this anymore (your code is based on a version from last
year sometime) ... See
ERXEOControlUtilities._aggregateFunctionWithQualifier for an
example of how to do it properly (we actually create an attribute
without adding it to the entity)
ms
On Mar 30, 2008, at 5:43 PM, Dov Rosenberg wrote:
We have some code that we are using from Project Wonder (I think)
that adds an attribute programmatically to an EOEntity to do
things like count, max, etc. (See below). We were doing a load
test on our application and started throwing errors because a
different query was submitted using the extra attribute. It seems
that making changes to the EOModel is not thread safe. If that is
the case is there anything we can do to use this code? Or should
we dump this and build a regular fetch for the aggregate data. Any
thooughts or insights would be a huge help.
Query that was generated in error – notice the COUNT() attribute
embedded in the query incorrectly
"SELECT t0.ACTUALRATING, t0.BODY, t0.CLOSED, t0.DATEADDED,
t0.DATEMODIFIED, t0.FORUMID, t0.IPADDRESS, t0.LOCALEID,
t0.MODERATE, COUNT(t0.RECORDID), t0.PUBLISHED, t0.RECORDID,
t0.STATUS, t0.TITLE, t0.TYPE, t0.USERID, t0.USERNAME,
t0.USERNICKNAME, t0.WEIGHTEDRATING FROM DBTOPIC t0 WHERE
t0.RECORDID = ?" withBindings:
1:"0032274bc94901122623a943007f46"(recordID)>:
Next exception:SQL State:42000 -- error code: 937 -- msg:
ORA-00937: not a single-group group function
This is the code that we use to add the temporary attribute.
public static Number
aggregateNumberFunctionWithQualifier(EOEditingContext ec, String
entityName, String attributeName, String function, EOQualifier
qualifier) { EOEntity entity = EOUtilities.entityNamed(ec,
entityName); NSArray results = null; EOAttribute
attribute = createAggregateAttribute(ec, function, attributeName,
entityName, "java.lang.Number", "i"); EOQualifier
schemaBasedQualifier =
entity.schemaBasedQualifier(qualifier);
EOFetchSpecification fs = new EOFetchSpecification(entityName,
schemaBasedQualifier, null); synchronized (entity)
{ entity.addAttribute(attribute);
try{ fs.setFetchesRawRows(true);
fs.setRawRowKeyPaths(new
NSArray(attribute.name())); results =
ec
.objectsWithFetchSpecification
(fs
); }finally
{ entity
.removeAttribute(attribute); } } if
((results != null) && (results.count() == 1))
{ NSDictionary row = (NSDictionary)
results.lastObject(); if
(row.objectForKey(attribute.name()) != null &&
row.objectForKey(attribute.name()) instanceof Number)
{ return (Number)
row.objectForKey(attribute.name()); } }
return null; }
Dov Rosenberg
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