Re: Expanding the "data_context" structure to include other Table

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1) Lets say the first request made is to "snmpwalk" through Table2. Are you saying that Table1's container_load() procedure has never been called yet so none of the index values have been loaded and none of the rows have been allocated and placed into the Table1 container yet? If this is true, then how does an "snmpwalk" through Table2 work since no rows have been allocated to store the data yet?

I am getting way confused. What actually happens when an "snmpwalk" of Table2 occurs first? Does the container_load() procedure of Table2 get called first? If so, then I am confused since I thought Table2's container_load() would not be reserving index values and not be performing any row allocation (basically not doing much of anything really) since I thought all of this would be handled in Table1 container_load() procedure only.

What exactly should be placed into the container_load() procedure of Table2? If you indicate I should be reserving index values and/or allocating rows for the container then I am confused since I thought all of this would be done in in Table1 functionality.

Actually, by now you understand I have a main Table1 (with 4 fields) and a Table2 (with 8 fields) which is an extension to Table1. Perhaps you can describe to me what functionality should be placed into the Table1_container_load(), Table1_row_prep(), Table2_container_load() and Table2_row_prep() routines? I think my problem is that I understand what the container_load and row_prep routines should do, but have no idea how to use them correctly when one of my tables is an extension of another table.

2) You state "Luckily, there is a failry easy way around that, which is sharing a single cache as well. See the function _ifXTable_container_init to see how it looks up the ifTable cache to share a container".

I looked at this code and can see how another table's cache can be connected to the container of another table. Perhaps you can explain to me "why" I should be doing this as am I not clear as to why you are recommending this code to me in the first place.

3) You stated "Now, the problem is that when you are loading the container, you will have no idea which of the 6 tables triggered the load."

Well this seems bad since I will not know what I am really loading? Are you indicating I should not be implementing it this way by adding all fields into the data_context of Table1? Is this your way of indicating to me that I will run into too many problems with combining all fields into the data_context of Table1 and that I should use sub-containers after all?

4) I wish you were local so I could stop by and have you simply draw some ideas on some paper as to what you are recommending. It is challenging for me to grasp how to do all of this as well as having no one here locally to bounce ideas around with. Again, thank you for your time and patience.




Robert Story <rstory@freesnmp.com> wrote: On Fri, 1 Jun 2007 12:54:20 -0700 (PDT) Need wrote:
NH> So Robert ..... instead of me implementing sub-containers, lets say I implement your other suggestion of adding all the fields defined in Table2,3,4,5,6 into the "data_context" structure for Table1. I believe I will be able to use a "union" to define these new fields within the structure to conserve space since each table is mutually exclusive to each other.

Ok.. there is one issue with sharing a single container, but you may not
care. The problem is that when walking the secondary tables, you will have to add code to each to make sure the current row index applies to the table in question, and then tell the agent to skip the row if it does not. So, if you have 1000 rows in Table1, and only 10 of which are in Table 2, there will be 990 wasted calls to Table2.

Also note that there currently is not any generated code to handle skipping an inappropriate row, as currently the assumption is that the container only has appropriate rows. But it should be fairly trivial to fix that.

NH> I assume the "container_load()" procedure of Table1 (main table) will be called first

That is an invalid assumption. By default, the container_load function is
called when a request comes in for a table. So it is possible that the first
query the agent gets will be for table2, and not table1. Luckily, there is a
failry easy way around that, which is sharing a single cache as well. See the function _ifXTable_container_init to see how it looks up the ifTable cache to share a container.

Now, the problem is that when you are loading the container, you will have no idea which of the 6 tables triggered the load.


NH> When the "container_load()" procedure for Table1 is called, I would like to populate all of Table1 fields at this time, however, must I populate all fields defined in Table2,3,4,5,6 at this time as well?
NH>
NH> If I do not populate the fields from Table2,3,4,5,6 at this time, then how will I be
NH> able to populate the fields later? Will the "container_load()" procedure for Table2,3,4,5,6 be called eventually and should I populate those fields at this time instead? If so, how will I know what correct table index (ie: row index) from Table1 the data should be inserted into at this time?

No, as I said before, you can use the row_prep function to delay the data
lookup until it is needed.

NH> Also, just curious .... when the cache expires, then I assume the "container_load()" procedure is called again to regenerate the complete table over again as it originally did ... is this correct? I assume new rows will be allocated again.

Be default, the container is flushed, and must be reloaded from scratch. But
you can set some cache attributes to prevent that, but then you must be
careful to correctly add new entries and remove old entries. See the ifTable
implementation for an example of one way to do this.



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1) Lets say the first request made is to "snmpwalk" through Table2.&nbsp;&nbsp; Are you saying that Table1's container_load() procedure has never been called yet so none of the index values have been loaded and none of the rows have been allocated and placed into the Table1 container yet?&nbsp; If this is true, then how does an "snmpwalk" through Table2 work since no rows have been allocated to store the data yet?<br><br>I am getting way confused.&nbsp;&nbsp; What actually happens when an "snmpwalk" of Table2 occurs first?&nbsp; Does the container_load() procedure of Table2 get called first?&nbsp; If so, then I am confused since I thought Table2's container_load() would not be reserving index values and not be performing any row allocation (basically not doing much of anything really) since I thought all of this would be handled in Table1 container_load() procedure only.<br><br>What exactly should be placed into the container_load() procedure of Table2?&nbsp; If you
indicate I should be reserving index values and/or allocating rows for the container then I am confused since I thought all of this would be done in in Table1 functionality.<br><br>Actually, by now you understand I have a main Table1 (with 4 fields) and a Table2 (with 8 fields) which is an extension to Table1.&nbsp;&nbsp; Perhaps you can describe to me what functionality should be placed into the Table1_container_load(), Table1_row_prep(), Table2_container_load() and Table2_row_prep() routines?&nbsp; I think my problem is that I understand what the container_load and row_prep routines should do, but have no idea how to use them correctly when one of my tables is an extension of another table.<br><br>2) You state "<span style="font-style: italic;">Luckily, there is a failry easy way around that, which is sharing a single cache as well. See the function _ifXTable_container_init to see how it looks up the ifTable cache to share a container</span>".&nbsp; <br><br>I looked at
this code and can see how another table's cache can be connected to the container of another table.&nbsp; Perhaps you can explain to me "why" I should be doing this as am I not clear as to why you are recommending this code to me in the first place.<br><br>3) You stated "<span style="font-style: italic;">Now, the problem is that when you are loading the container, you will have no idea which of the 6 tables triggered the load.</span>"&nbsp;&nbsp; <br><br>Well this seems bad since I will not know what I am really loading? &nbsp; Are you indicating I should not be implementing it this way by adding all fields into the data_context of Table1?&nbsp; Is this your way of indicating to me that I will run into too many problems with combining all fields into the data_context of Table1 and that I should use sub-containers after all?<br><br>4) I wish you were local so I could stop by and have you simply draw some ideas on some paper as to what you are recommending.&nbsp;&nbsp; It is
challenging for me to grasp how to do all of this as well as having no one here locally to bounce ideas around with.&nbsp; Again, thank you for your time and patience.<br><br><br><br><br><b><i>Robert Story &lt;rstory@freesnmp.com&gt;</i></b> wrote:<blockquote class="replbq" style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"> On Fri, 1 Jun 2007 12:54:20 -0700 (PDT) Need wrote:<br>NH&gt; So Robert ..... instead of me implementing sub-containers, lets say I implement your other suggestion of adding all the fields defined in Table2,3,4,5,6 into the "data_context" structure for Table1. I believe I will be able to use a "union" to define these new fields within the structure to conserve space since each table is mutually exclusive to each other.<br><br>Ok.. there is one issue with sharing a single container, but you may not<br>care. The problem is that when walking the secondary tables, you will have to add code to each to make sure the
current row index applies to the table in question, and then tell the agent to skip the row if it does not. So, if you have 1000 rows in Table1, and only 10 of which are in Table 2, there will be 990 wasted calls to Table2.<br><br>Also note that there currently is not any generated code to handle skipping an inappropriate row, as currently the assumption is that the container only has appropriate rows. But it should be fairly trivial to fix that.<br><br>NH&gt; I assume the "container_load()" procedure of Table1 (main table) will be called first<br><br>That is an invalid assumption. By default, the container_load function is<br>called when a request comes in for a table. So it is possible that the first<br>query the agent gets will be for table2, and not table1. Luckily, there is a<br>failry easy way around that, which is sharing a single cache as well. See the function _ifXTable_container_init to see how it looks up the ifTable cache to share a container.<br><br>Now, the
problem is that when you are loading the container, you will have no idea which of the 6 tables triggered the load.<br><br><br>NH&gt; When the "container_load()" procedure for Table1 is called, I would like to populate all of Table1 fields at this time, however, must I populate all fields defined in Table2,3,4,5,6 at this time as well?<br>NH&gt; <br>NH&gt; If I do not populate the fields from Table2,3,4,5,6 at this time, then how will I be<br>NH&gt; able to populate the fields later? Will the "container_load()" procedure for Table2,3,4,5,6 be called eventually and should I populate those fields at this time instead? If so, how will I know what correct table index (ie: row index) from Table1 the data should be inserted into at this time?<br><br>No, as I said before, you can use the row_prep function to delay the data<br>lookup until it is needed.<br><br>NH&gt; Also, just curious .... when the cache expires, then I assume the "container_load()" procedure is called again
to regenerate the complete table over again as it originally did ... is this correct? I assume new rows will be allocated again.<br><br>Be default, the container is flushed, and must be reloaded from scratch. But<br>you can set some cache attributes to prevent that, but then you must be<br>careful to correctly add new entries and remove old entries. See the ifTable<br>implementation for an example of one way to do this.<br></blockquote><br><p>

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