I want to know if there is any risks involved when changing a table's schema, for example from dbo. to xyz. or visa versa.
Would like to hear your views on this.
First which crossed my mind is when you have views, stored procedures etc which contains query like
SELECT *
FROM [sch].[tbl]
Once you move table to new schema you will get 'Invalid object name 'oldSchema.tableName'.
Related
The idea of the SaaS tool is to have dynamic tables with dynamic custom fields and values of different types, we were thinking to use "force.com/salesforce.com" example but is seems to be too complicated to maintain moving forward, also making some reports to create with a huge abstraction level, so we came up with simple idea but we have to be sure that this is kinda good approach.
This is the architecture we have today (in few steps).
Each tenant has it own separate database on the cluster (Postgres 12).
TABLE table, used to keep all of those tables as reference, this entity has ManyToOne relation to META table and OneToMany relation with DATA table.
META table is used for metadata configuration, has OneToMany relation with FIELDS (which has name of the fields as well as the type of field e.g. TEXT/INTEGER/BOOLEAN/DATETIME etc. and attribute value - as string, only as reference).
DATA table has ManyToOne relation to TABLES and 50 character varying columns with names like: attribute1...50 which are NULL-able.
Example flow today:
When user wants to open a TABLE DATA e.g. "CARS", we load the META table with all the FIELDS (to get fields for this query). User specified that he want to query against: Brand, Class, Year, Price columns.
We are checking by the logic, the reference for Brand, Class, Year and Price in META>FIELDS table, so we know that Brand = attribute2, Class = attribute 5, Year = attribute6 and Price = attribute7.
We parse his request into a query e.g.: SELECT [attr...2,5,6,7] FROM DATA and then show the results to user, if user decide to do some filters on it, based on this data e.g. Year > 2017 AND Class = 'A' we use CAST() functionality of SQL for example SELECT CAST(attribute6 AS int) AND attribute5 FROM DATA WHERE CAST(attribute6 AS int) > 2017 AND attribute5 = 'A';, so then we can actually support most principles of SQL.
However moving forward we are scared a bit:
Manage such a environment for more tenants while we are going to have more tables (e.g. 50 per customer, with roughly 1-5 mil per TABLE (5mil is maximum which we allow, for bigger data we have BigQuery) which is giving us 50-250 mil rows in single table DATA_X) which might affect performance of the queries, especially when we gave possibilities to manage simple WHERE statements (less,equal,null etc.) using some abstraction language e.g. GET CARS [BRAND,CLASS,PRICE...] FILTER [EQ(CLASS,A),MT(YEAR,2017)] developed to be similar to JQL (Jira Query Language).
Transactions lock, as we allow to batch upload CSV into the DATA_X so once they want to load e.g. 1GB of the data, it kinda locks the table for other systems to access the DATA table.
Keeping multiple NULL columns which can affect space a bit (for now we are not that scared as while TABLE creation, customer can decide how many columns he wants, so based on that we are assigning this TABLE to one of hardcoded entities DATA_5, DATA_10, DATA_15, DATA_20, DATA_30, DATA_50, where numbers corresponds to limitations of the attribute columns, and those entities are different, we also support migration option if they decide to switch from 5 to 10 attributes etc.
We are on super early stage, so we can/should make those before we scale, as we knew that this is most likely not the best approach, but we kept it to run the project for small customers which for now is working just fine.
We were thinking also about JSONB objects but that is not the option, as we want to keep it simple for getting the data.
What do you think about this solution (fyi DATA has PRIMARY key out of 2 tables - (ID,TABLEID) and built in column CreatedAt which is used form most of the queries, so there will be maximum 3 indexes)?
If it seem bad, what would you recommend as the alternative to this solution based on the details which I shared (basically schema-less RDBMS)?
IMHO, I anticipate issues when you wanted to join tables and also using cast etc.
We had followed the approach below that will be of help to you
We have a table called as Cars and also have a couple of tables like CarsMeta, CarsExtension columns. The underlying Cars table will have all the common fields for a ll tenant's. Also, we will have the CarsMeta table point out what are the types of columns that you can have for extending the Cars entity. In the CarsExtension table, you will have columns like StringCol1...5, IntCol1....5, LongCol1...10
In this way, you can easily filter for data also like,
If you have a filter on the base table, perform the search, if results are found, match the ids to the CarsExtension table to get the list of exentended rows for this entity
In case the filter is on the extended fields, do a search on the extension table and match with that of the base entity ids.
As we will have the extension table organized like below
id - UniqueId
entityid - uniqueid (points to the primary key of the entity)
StringCol1 - string,
...
IntCol1 - int,
...
In this case, it will be easy to do a join for entity and then get the data along with the extension fields.
In case you are having the table metadata and data being inferred from separate tables, it will be a difficult task to maintain this over long period of time and also huge volume of data.
HTH
I have a table with several fields, this table almost never change but for one field, "version" which change very often.
Would it be relevant to put that single field into a separate table in order to reduce how often locks are put on the main table?
For instance I have a table tType and a table tEntry.
Whenever I add/deleted/update any row of tEntry, I need to update the "version" field of tType. There might be thousand of rows inside tEntry for a single tType referenced row. Meaning the version number could change very often, though any other data of tType (such as name, id, etc.) doesn't change.
Your Referral to tType and tEntry sounds like you are implementing a key-value store in a rdbms. There are several discussions you can google about this topic. In the www there seems to be consesus, that cons overweight pros on that. An option would be to look at key value stores, no sql, multi column DBs, etc (wikipedia)...
The next "anti-pattern" I recognized is that you try to mix transactional data with 'master data' in the table tType. Try to avoid this, even if your selects get more uncomfortable and need to be tuned better. Keep off the version info from the tType, if this changes extremely often. Look here to get the concept: MySQL JOIN the most recent row only?
I would like to use a parameter for the table name. I have an application that creates several new tables each month. I therefore need the table name to be sent into CR via a parameter. The fields for the tabkes are always identical. I can present a list (view) from the database to the end user that would display a user friendly name for the table, when the user selects the instance they want I then have the table name I want to report from.
I'm not sure if that is possible. Even if your tables have the same structure, the field names will ultimately be different. Let's say you have a {table1.field1} in your report. Now you want to run the report from table2 instead of table1. So your field now would have to become {table2.field1}. Does that make sense? I think a better approach might be to try stored procedures that will create the fields you need so the field names won't change.
I'm new to Filemaker and need some advice on auto-populating tables.
Part 1:
I have TableA which includes many records with client information. I want a separate TableB which is identical to TableA except that it is "de-identified"; that is, it does not contain two of the fields, first name and last name.
I would like the two tables to interact such that if I add a new record to TableA, that same record (sans first and last name) appear automatically in TableB.
Part 2:
In addition to the above functionality, I would also like said functionality to be dependent on a specific field type from TableA. For example, I enter a new record, which has a "status" field set to "active," into tableA. I then want that record to be auto-popualted into TableB; however, if I add another record with a "status" of "inactive," I want that that record auto-populated into a TableC but not into TableB.
FileMaker can perform this with script triggers so long as every layout where TableA will be edited has a layout script trigger of OnRecordCommit connected to it. When the record is committed (which can happen in a number of ways), the attached script will run, which you can use to create the appropriate record in the appropriate table.
The script could create the record in a number of ways. If the primary keys for both records are the same, you could use lookups. You could export the record in TableA and then import it into the correct table. You could pass the field information as a parameter to the script. The best choice really depends on your needs.
Having said that, I would question the wisdom of this approach. It brings up a few questions that would seem to complicate matters. For example, what happens when the status changes? When a record in TableA is deleted? When fields in TableA are modified? Each of these contingencies (and others) will require thought and more complicated scripts.
So I would ask what problem you're really trying to solve. My best guess is that you are trying to keep the name information private from certain users. User accounts and privileges with dedicated layouts for each privilege can solve this without the need for duplicate tables. FileMaker privilege sets can be quite granular.
For example, you can specify that users with PrivilegeA can create records and view names, but PrivilegeB users can only view records if the status is "active" and the name fields are not available to them, while PrivilegeC users can view records if the status is "inactive" and the name fields are also not available to them.
I would definitely use filters and permissions on the "status field" to achieve this and not two mirroring tables. Unless the inactive information is drastically different, you would be complicated your solution and creating more possible pitfalls.
I have a database, with every users having a schema.
Is there a way to query a table in every schema?
Something like: select id, name from *.simulation doesn't work...
Thank you for your help !
No, you will need to write a function - either a server side function or a client side function in whatever language you're using - that executes the query once for each schema.
You could also create a VIEW that does UNION ALL between all the schemas, but that's going to be a lot of work to maintain if your schemas are dynamically added and removed.
Yes you can, use SET search_path TO ... to point to all schema's. If you don't know all the names of the schemas, wrap it in a function that first selects all schemas and then set the entire search_path.
http://www.postgresql.org/docs/current/interactive/sql-set.html