Re: How to avoid expensive fetches in database when setting to-one-relationship

Subject: Re: How to avoid expensive fetches in database when setting to-one-relationship
From: Jérémy DE ROYER <email@hidden>
Date: Sun, 05 Jun 2016 22:26:41 +0000
Thread-topic: How to avoid expensive fetches in database when setting to-one-relationship

What do you mean with « you can still use it for fetching » ?

I removed the class property for the Customer to Order (but keeped the « listOrder » relationship)

When I set the customer to the order, it runs fast.

But when I retrieve the orders using the method below :

  public NSArray<Customer> listOrder() {

    return (NSArray<Customer>)storedValueForKey("listOrder");

}

I get an error :

<com.webobjects.foundation.NSKeyValueCoding$UnknownKeyException message ‘<Customer 0x72c7423b> valueForKey(): lookup of unknown key: 'listOrder'.

This class does not have an instance variable of the name listOrder or _listOrder, nor a method of the name listOrder  _listOrder, getListOrder, or _getListOrder' object ‘{...}' key 'listOrder'>

at com.webobjects.foundation.NSKeyValueCoding$DefaultImplementation.handleQueryWithUnboundKey(NSKeyValueCoding.java:1377)

at com.webobjects.eocontrol.EOCustomObject.handleQueryWithUnboundKey(EOCustomObject.java:1545)

at com.webobjects.foundation.NSKeyValueCoding$Utility.handleQueryWithUnboundKey(NSKeyValueCoding.java:494)

at com.webobjects.foundation.NSKeyValueCoding$_KeyBinding.valueInObject(NSKeyValueCoding.java:894)

at com.webobjects.eocontrol.EOCustomObject.storedValueForKey(EOCustomObject.java:1634)

at Customer.listeOrder(_Customer.java:890)

Where am I wrong ?

Jérémy

Le 5 juin 2016 à 22:04, Chuck Hill <email@hidden> a écrit :

Remove the “class property” setting for the ModeTransport to Order. You can still use it for fetching.

Chuck

From: <webobjects-dev-bounces+chill=email@hidden> on behalf of Jérémy DE ROYER <email@hidden>
Date: Sunday, June 5, 2016 at 12:55 PM
To: WebObjects-Dev <email@hidden>
Subject: How to avoid expensive fetches in database when setting to-one-relationship

Dear all,

In our app, we have a one to many relationship between order and mode transport

For each order, we set the mode transport using the method below :

  public void setModeTransportRelationship(ModeTransport value) {

  if (_CommandeClient.LOG.isDebugEnabled()) {

_CommandeClient.LOG.debug("updating modeTransport from " + modeTransport() + " to " + value);

}

  if (value == null) {

ModeTransport oldValue = modeTransport();

  if (oldValue != null) {

removeObjectFromBothSidesOfRelationshipWithKey(oldValue, "modeTransport");

}

} else {

addObjectToBothSidesOfRelationshipWithKey(value, "modeTransport");

}

}

Then, an objectWillChange() is fired for the mode transport… but the (not wished) consequence is that every to many relationships from the mode transport are fetched (even if we don’t call the associated method for the mode transport). However, the objects associated with the to one relationships are not fetched.

We observed the same behavior for the customer object when using the setCustomerRelationship method of the ordre. The (bigger) problem is that the customer object has dozen of to many relationships... fetched for nothing…

At the beginning we had few orders but now, we have to wait from 10 to 30 seconds until de saveChange is ended and that’s really not effective. More than 90 % of this time is spent for fetching the to many relationship whereas we just had to save the order values...

Any idea how to deal with theses not-wished-fetches ?

Jérémy

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References:
	>How to avoid expensive fetches in database when setting to-one-relationship (From: Jérémy DE ROYER <email@hidden>)
	>Re: How to avoid expensive fetches in database when setting to-one-relationship (From: Chuck Hill <email@hidden>)

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