I've used SqlSyncScopeProvisioning to create ScopeA ScopeB and ScopeC. Each corresponds to a single table, TableA TableB TableC. There are no filters, and all the data is syncing between the servers correctly.
I'd now like to clean up the scopes and have a single scope to cover all of the tables, instead of 3 scopes. Let's call it ScopeAll.
If I provision ScopeAll containing TableA TableB TableC, will it copy the existing knowledge data from ScopeA ScopeB ScopeC so that the initial data does not need to all be copied over and sync'd again?
After that I would then deprovision ScopeA ScopeB and ScopeC.
no, it will not copy the sync knowledge. a scope doesn't care about any other scope in the database.
Related
Users & Scope -
write_user - All Access to all Tables
read_user - Read access to all Tables
backup_pruner - All GRANTS to all tables in schema backup.
My Problem Statement -
I have written an automation that has to drop tables of a schema called backup where tables are created by write_user.
Now, for dropping tables I have to user the backup_pruner user and here is the problem.
Since write_user creates table here, it is the owner of all tables in backup & Only Owners/Super-Users can drop tables.
How to Proceed from here ?
To answer the question WHY to use a separate user to DROP Tables -
To tighten the accessibility of tables as DROP if not used properly/any corner case, then can be disastrous for other tables too.
Consider using a Stored Procedure created with the SECURITY DEFINER to drop the tables. An SP created this way runs with the permissions of the creator.
You can define a list of table names allowed to be dropped that the SP checks before taking action.
I created an example of this approach on GitHub: sp_controlled_access
I'm using ColdFusion to connect to a RedShift database and I'm trying to understand how to test/assume myself of how the connections work in relation to TEMP tables in RedShift.
In my CFADMIN for the datasource I have unchecked Maintain connections across client requests. I would assume then each user who is using my website would have their own "Connection" to the DB? Is that correct?
Per the RedShift docs about temp tables:
TEMP: Keyword that creates a temporary table that is visible only within the current session. The table is automatically dropped at the end of the session in which it is created. The temporary table can have the same name as a permanent table. The temporary table is created in a separate, session-specific schema. (You cannot specify a name for this schema.) This temporary schema becomes the first schema in the search path, so the temporary table will take precedence over the permanent table unless you qualify the table name with the schema name to access the permanent table.
Am I to understand that if #1 is true and each user has their own connection to the database and thereby their own session then per #2 any tables that are created will be only in that session even though the "user" is the same as it's a connection from my server that is using the same credentials.
3.If my assumptions in #1 and #2 are correct then if I have ColdFusion code that runs a query like so:
drop if exists tablea
create temp table tablea
insert into tablea
select * from realtable inner join
drop tablea
And multiple users are using that same function that does this. They should never run into any conflicts where one table gets dropped as another request is trying to use it correct?
How do I test that this is the case? Besides throwing it into production and waiting for an error how can I know. I tried running a few windows side by side in different browsers and stuff and didn't notice an issue, but I don't know how to know if the temp tables truly are different between clients. (as they should be.) I imagine I could query some meta data but what meta data about the table would tell me that?
I have a similar situation, but with redbrick database software. I handle it by creating unique table names. The general idea is:
Create a table name something like this:
<cfset tablename = TableText & randrange(1, 100000)>
Try to create a table with that name. If you fail try again with a different name.
If you fail 3 times stop trying and mail the cfcatch information to someone.
I have all this code in a custom tag.
Edit starts here
Based on the comments, here is some more information about my situation. In CFAdmin, for the datasource being discussed, the Maintain Connections box is checked.
I put this code on a ColdFusion page:
<cfquery datasource="dw">
create temporary table dan (f1 int)
</cfquery>
I ran the page and then refreshed it. The page executed successfully the first time. When refreshed, I got this error.
Error Executing Database Query.
** ERROR ** (7501) Name defined by CREATE TEMPORARY TABLE already exists.
That's why I use unique tablenames. I don't cache the queries though. Ironically, my most frequent motivation for using temporary tables is because there are situations where they make things run faster than using the permanent tables.
I think this is a recurrent question in the Internet, but unfortunately I'm still unable to find a successful answer.
I'm using Ruby on Rails 4 and I would like to create a model that interfaces with a SQL query, not with an actual table in the database. For example, let's suppose I have two tables in my database: Questions and Answers. I want to make a report that contains statistics of both tables. For such purpose, I have a complex SQL statement that takes data from these tables to build up the statistics. However the SELECT used in the SQL statement does not directly take values from neither Answers nor Questions tables, but from nested SELECTs.
So far I've been able to create the StatItem model, without any migration, but when I try StatItem.find_by_sql("...nested selects...") the system complains about unexisting table stat_items in the database.
How can I create a model whose instance's data is retrieved from a complex query and not from a table? If it's not possible, I could create a temporary table to store the data in there. In such case, how can I tell the migration file to not create such table (it would be created by the query)?
How about creating a materialized view from your complex query and following this tutorial:
ActiveRecord + PostgreSQL Materialized Views
Michael Kohl and his proposal of materialized views has given me an idea, which I initially discarded because I wrongly thought that a single database connection could be shared by two processes, but after reading about how Rails processes requests, I think my solution is fine.
STEP 1 - Create the model without migration
rails g model StatItem --migration=false
STEP 2 - Create a temporary table called stat_items
#First, drop any existing table created by older requests (database connections are kept open by the server process(es).
ActiveRecord::Base.connection.execute('DROP TABLE IF EXISTS stat_items')
#Second, create the temporary table with the desired columns (notice: a dummy column called 'id:integer' should exist in the table)
ActiveRecord::Base.connection.execute('CREATE TEMP TABLE stat_items (id integer, ...)')
STEP 3 - Execute an SQL statement that inserts rows in stat_items
STEP 4 - Access the table using the model, as usual
For example:
StatItem.find_by_...
Any comments/improvements are highly appreciated.
I realized that you can add a scope for the whole database or just a number of tables.
The question would be, if you're going to synchronize a full database, which would be preferrable, one scopename for the whole database, or would it be better to scope and synchronize per schema?
that would depend on some factors: number of tables, frequency of update, sync direction, etc...
have a look at this: SYNC FRAMEWORK SCOPE AND SQL AZURE DATA SYNC DATASET CONSIDERATIONS
I am using Microsoft Synch Service Framework 4.0 for synching Sql server Database tables with SqlLite Database on the Ipad side.
Before making any Database schema changes in the Sql Server Database, We have to Deprovision the database tables. ALso after making the schema changes, we ReProvision the tables.
Now in this process, the tracking tables( i.e. the Synching information) gets deleted.
I want the tracking table information to be restored after Reprovisioning.
How can this be done? Is it possible to make DB changes without Deprovisioning.
e.g, the application is in Version 2.0, The synching is working fine. Now in the next version 3.0, i want to make some DB changes. SO, in the process of Deprovisioning-Provisioning, the tracking info. gets deleted. So all the tracking information from the previous version is lost. I do not want to loose the tracking info. How can i restore this tracking information from the previous version.
I believe we will have to write a custom code or trigger to store the tracking information before Deprovisioning. Could anyone suggest a suitable method OR provide some useful links regarding this issue.
the provisioning process should automatically populate the tracking table for you. you don't have to copy and reload them yourself.
now if you think the tracking table is where the framework stores what was previously synched, the answer is no.
the tracking table simply stores what was inserted/updated/deleted. it's used for change enumeration. the information on what was previously synched is stored in the scope_info table.
when you deprovision, you wipe out this sync metadata. when you synch, its like the two replicas has never synched before. thus you will encounter conflicts as the framework tries to apply rows that already exists on the destination.
you can find information here on how to "hack" the sync fx created objects to effect some types of schema changes.
Modifying Sync Framework Scope Definition – Part 1 – Introduction
Modifying Sync Framework Scope Definition – Part 2 – Workarounds
Modifying Sync Framework Scope Definition – Part 3 – Workarounds – Adding/Removing Columns
Modifying Sync Framework Scope Definition – Part 4 – Workarounds – Adding a Table to an existing scope
Lets say I have one table "User" that I want to synch.
A tracking table will be created "User_tracking" and some synch information will be present in it after synching.
WHen I make any DB changes, this Tracking table "User_tracking" will be deleted AND the tracking info. will be lost during the Deprovisioning- Provisioning process.
My workaround:
Before Deprovisioning, I will write a script to copy all the "User_tracking" data into another temporary table "User_tracking_1". so all the existing tracking info will be stored in "User_tracking_1". WHen I reprovision the table, a new trackin table "User_Tracking" will be created.
After Reprovisioning, I will copy the data from table "User_tracking_1" to "User_Tracking" and then delete the contents from table "User_Tracking_1".
UserTracking info will be restored.
Is this the right approach...