I have two Postgresql databases (on different servers): lets call them stable and unstable. The stable is for read purposes only. From time to time the the stable is updated to the current unstable.
I would like to improve the update process. Dumping to a file and restoring is not possible any more due to the size of database. I found many replication tools designed for a master-slave configuration, but that is not exactly what I do, as the slave (stable) is updated on demand. The tools seem to be more complicated that the problem I want them to solve.
Ideally, I would like a simple tool with interface like pg_replicate source target which would result in target db being exact clone of source and the data being transfered directly between the two database servers (they are connected by a local network) without creating large temporary files. The database size is 50 GB and growing, so transfering SQL inserts might not suffice.
So, is there a tool which could do it? Or anything close?
Related
I have imported about 200 GB of census data into a postgreSQL 9.3 database on a Windows 7 box. The import process involves many files and has been complex and time-consuming. I'm just using the database as a convenient container. The existing data will rarely if ever change, and will be updating it with external data at most once a quarter (though I'll be adding and modifying intermediate result columns on a much more frequent basis. I'll call the data in the database on my desktop the “master.” All queries will come from the same machine, not remote terminals.
I would like to put copies of all that data on three other machines: two laptops, one windows 7 and one Windows 8, and on a Ubuntu virtual machine on my Windows 7 desktop as well. I have installed copies of postgreSQL 9.3 on each of these machines, currently empty of data. I need to be able to do both reads and writes on the copies. It is OK, and indeed I would prefer it, if changes in the daughter databases do not propagate backwards to the primary database on my desktop. I'd want to update the daughters from the master 1 to 4 times a year. If this wiped out intermediate results on the daughter databases this would not bother me.
Most of the replication techniques I have read about seem to be worried about transaction-by-transaction replication of a live and constantly changing server, and perfect history of queries & changes. That is overkill for me. Is there a way to replicate by just copying certain files from one postgreSQL instance to another? (If replication is the name of a specific form of copying, I'm trying to ask the more generic question). Or maybe by restoring each (empty) instance from a backup file of the master? Or of asking postgreSQL to create and export (ideally on an external hard drive) some kind of postgreSQL binary of the data that another instance of postgreSQL can import, without my having to define all the tables and data types and so forth again?
This question is also motivated by my desire to work around a home wifi/lan setup that is very slow – a tenth or less of the speed of file copies to an external hard drive. So if there is a straightforward way to get the imported data from one machine to another by transference of (ideally compressed) binary files, this would work best for my situation.
While you could perhaps copy the data directory directly as mentioned by Nick Barnes in the comments above, I would recommend using a combination of pg_dump and pg_restore, which will dump a self-contained file which can then be dispersed to the other copies.
You can run pg_dump on the master to get a dump of the DB. I would recommend using the options -Fc -j3 to use the custom binary format (instead of dumping in SQL format; this should be much smaller and perhaps faster as well) and will dump 3 tables at once (this can be adjusted up or down depending on the disk throughput capabilities of your machine and the number of cores that it has).
Then you run dropdb on the copies, createdb to recreate an empty DB of the same name, and then run pg_restore on that new empty DB to restore the dump file to the DB. You would want to use the options -d <dbname> -f <dump_file> -j3 (again adjusting the number for -j according to the abilities of the machine).
When you want to refresh the copies with new content from the master DB, simply repeat the above steps
I'm looking for a little advice.
I have some SQL Server tables I need to move to local Access databases for some local production tasks - once per "job" setup, w/400 jobs this qtr, across a dozen users...
A little background:
I am currently using a DSN-less approach to avoid distribution issues
I can create temporary LINKS to the remote tables and run "make table" queries to populate the local tables, then drop the remote tables. Works as expected.
Performance here in US is decent - 10-15 seconds for ~40K records. Our India teams are seeing >5-10 minutes for the same datasets. Their internet connection is decent, not great and a variable I cannot control.
I am wondering if MS Access is adding some overhead here than can be avoided by a more direct approach: i.e., letting the server do all/most of the heavy lifting vs Access?
I've tinkered with various combinations, with no clear improvement or success:
Parameterized stored procedures from Access
SQL Passthru queries from Access
ADO vs DAO
Any suggestions, or an overall approach to suggest? How about moving data as XML?
Note: I have Access 7, 10, 13 users.
Thanks!
It's not entirely clear but if the MSAccess database performing the dump is local and the SQL Server database is remote, across the internet, you are bound to bump into the physical limitations of the connection.
ODBC drivers are not meant to be used for data access beyond a LAN, there is too much latency.
When Access queries data, is doesn't open a stream, it fetches blocks of it, wait for the data wot be downloaded, then request another batch. This is OK on a LAN but quickly degrades over long distances, especially when you consider that communication between the US and India has probably around 200ms latency and you can't do much about it as it adds up very quickly if the communication protocol is chatty, all this on top of the connection's bandwidth that is very likely way below what you would get on a LAN.
The better solution would be to perform the dump locally and then transmit the resulting Access file after it has been compacted and maybe zipped (using 7z for instance for better compression). This would most likely result in very small files that would be easy to move around in a few seconds.
The process could easily be automated. The easiest is maybe to automatically perform this dump every day and making it available on an FTP server or an internal website ready for download.
You can also make it available on demand, maybe trough an app running on a server and made available through RemoteApp using RDP services on a Windows 2008 server or simply though a website, or a shell.
You could also have a simple windows service on your SQL Server that listens to requests for a remote client installed on the local machines everywhere, that would process the dump and sent it to the client which would then unpack it and replace the previously downloaded database.
Plenty of solutions for this, even though they would probably require some amount of work to automate reliably.
One final note: if you automate the data dump from SQL Server to Access, avoid using Access in an automated way. It's hard to debug and quite easy to break. Use an export tool instead that doesn't rely on having Access installed.
Renaud and all, thanks for taking time to provide your responses. As you note, performance across the internet is the bottleneck. The fetching of blocks (vs a continguous DL) of data is exactly what I was hoping to avoid via an alternate approach.
Or workflow is evolving to better leverage both sides of the clock where User1 in US completes their day's efforts in the local DB and then sends JUST their updates back to the server (based on timestamps). User2 in India, also has a local copy of the same DB, grabs just the updated records off the server at the start of his day. So, pretty efficient for day-to-day stuff.
The primary issue is the initial DL of the local DB tables from the server (huge multi-year DB) for the current "job" - should happen just once at the start of the effort (~1 wk long process) This is the piece that takes 5-10 minutes for India to accomplish.
We currently do move the DB back and forth via FTP - DAILY. It is used as a SINGLE shared DB and is a bit LARGE due to temp tables. I was hoping my new timestamped-based push-pull of just the changes daily would have been an overall plus. Seems to be, but the initial DL hurdle remains.
I have multiple ~50MB Access 2000-2003 databases (MDB files) that only contain tables with data. The data-databases are located on a server in my enterprise that can take ~1-2 second to respond (and about 10 seconds to actually open the 50 MDB file manually while browsing in the file explorer). I have other databases that only contain forms. Most of those forms-database (still MDB files) are actually copied from the server to the client (after some testing, the execution looks smoother) before execution with a batch file. Most of those forms-databases use table-links to fetch the data from the data-databases.
Now, my question is: is there any advantage/disadvantage to merge all data-databases from my ~50MB databases to make one big database (let's say 500MB)? Will it be slower? It would actually help to clean up my code if I wouln't have to connect to all those different databases and I don't think 500MB is a lot, but I don't pretend to be really used to Access by any mean and that's why I'm asking. If Access needs to read the whole MDB file to get the data from a specific table, then it would be slower. It wouldn't be really that surprising from Microsoft, but I've been pleased so far with MS Access database performances.
There will never be more than ~50 people connected to the database at the same time (most likely, this number won't in fact be more than 10, but I prefer being a little bit conservative here just to be sure).
The db engine does not read the entire MDB file to get information from a specific table. It must read information from the system tables (hidden tables whose names start with MSys) to determine where the data you need is stored. Furthermore, if you're using a query to retrieve information from the table, and the db engine can use an index to determine which rows satisfy the query's WHERE clause, it may read only those rows from the table.
However, you have issues with your network's performance. When those lead to dropped connections, you risk corrupting the MDB. That is why Access is not well suited for use in wide area networks or with wireless connections. And even on a wired LAN, you can suffer such problems when the network is flaky.
So while reducing the amount of data you pull across the network is a good thing, it is not the best remedy for Access on a flaky network. Instead you should migrate the data to a client-server db so it can be kept safe in spite of dropped connections.
You are walking on thin ice here.
Access will handle your scenario, but is not really meant to allow so many concurrent connections.
Merging everything in a big database (500mb) is not a wise move.
Have you tried to open it from a network location?
As far as I can suggest, I will use a backend SqlServer Express to merge all the tables in a single real client-server database.
The changes required by client mdb front-end should not be very pervasive.
I am build an application which needs to consume data from a source database. The source database has several issues including:
Performance issues
Legacy structure with terrible keys, naming conventions, etc.
Lots of data my application doesn’t care about
I would like to setup an application specific SQL Server database. The new database will be populated with a subset of data from the source database (and from a few other source systems). The data will always move one way from the source databases to the application specific database (i.e. - data won't sync back to the source). It will have a different DDL model than the source database.
The data doesn't need to be synced absolutely real time, but any longer than a few minute lag could cause issues.
How should I move data from the source database into the application database? Should I use
Replication
Write Custom SSIS Packages
Abstact to higher level SOA
solution like nServiceBus, AppFabric, etc?
Some other ideas?
Pros/cons to each?
Sounds to me like you don't need a messaging service like NServiceBus - this would involve modifying the legacy system to publish events whenever data changes, something I expect you don't want to get into. Because it is acceptable in your case for your local store of data to be slightly out of date, an SSIS package could be acceptable.
However, if the source database is very large, this could be an issue, as you will be doing it every few minutes. Also, if users of the legacy system are already experiencing performance problems, an SSIS package running every few minutes won't help. Maybe you could introduce a timestamp of the source data, so that it only copies new/modified data?
If the source data is very large and performance is seriously an issue, then maybe NServiceBus would be a good idea. You could also consider Mass Transit or your own simple solution built on MSMQ. But this will mean getting you hands dirty with the legacy code.
I'm writing a system at the moment that needs to copy data from a clients locally hosted SQL database to a hosted server database. Most of the data in the local database is copied to the live one, though optimisations are made to reduce the amount of actual data required to be sent.
What is the best way of sending this data from one database to the other? At the moment I can see a few possibly options, none of them yet stand out as being the prime candidate.
Replication, though this is not ideal, and we cannot expect it to be supported in the version of SQL we use on the hosted environment.
Linked server, copying data direct - a slow and somewhat insecure method
Webservices to transmit the data
Exporting the data we require as XML and transferring to the server to be imported in bulk.
The data copied goes into copies of the tables, without identity fields, so data can be inserted/updated without any violations in that respect. This data transfer does not have to be done at the database level, it can be done from .net or other facilities.
More information
The frequency of the updates will vary completely on how often records are updated. But the basic idea is that if a record is changed then the user can publish it to the live database. Alternatively we'll record the changes and send them across in a batch on a configurable frequency.
The amount of records we're talking are around 4000 rows per table for the core tables (product catalog) at the moment, but this is completely variable dependent on the client we deploy this to as each would have their own product catalog, ranging from 100's to 1000's of products. To clarify, each client is on a separate local/hosted database combination, they are not combined into one system.
As well as the individual publishing of items, we would also require a complete re-sync of data to be done on demand.
Another aspect of the system is that some of the data being copied from the local server is stored in a secondary database, so we're effectively merging the data from two databases into the one live database.
Well, I'm biased. I have to admit. I'd like to hypnotize you into shelling out for SQL Compare to do this. I've been faced with exactly this sort of problem in all its open-ended frightfulness. I got a copy of SQL Compare and never looked back. SQL Compare is actually a silly name for a piece of software that synchronizes databases It will also do it from the command line once you have got a working project together with all the right knobs and buttons. Of course, you can only do this for reasonably small databases, but it really is a tool I wouldn't want to be seen in public without.
My only concern with your requirements is where you are collecting product catalogs from a number of clients. If they are all in separate tables, then all is fine, whereas if they are all in the same table, then this would make things more complicated.
How much data are you talking about? how many 'client' dbs are there? and how often does it need to happen? The answers to those questions will make a big difference on the path you should take.
There is an almost infinite number of solutions for this problem. In order to narrow it down, you'd have to tell us a bit about your requirements and priorities.
Bulk operations would probably cover a wide range of scenarios, and you should add that to the top of your list.
I would recommend using Data Transformation Services (DTS) for this. You could create a DTS package for appending and one for re-creating the data.
It is possible to invoke DTS package operations from your code so you may want to create a wrapper to control the packages that you can call from your application.
In the end I opted for a set of triggers to capture data modifications to a change log table. There is then an application that polls this table and generates XML files for submission to a webservice running at the remote location.