June 19, 2013

Post: Multiple column index vs multiple indexes

Multiple Indexes vs Two Column Index efficiency. I mentioned in most cases when query can use both of the ways using multiple… sum(length(val)) FROM T WHERE i=2 OR j=1 Q5 SELECT sum(length(val)) FROM… it is currently implemented so they would use single index range scan. The 2 indexes however benefits…

Post: Distributed Set Processing with Shard-Query

…that are based on only a single base table. Knowing this, the query result set is treated …. There is no external locking or synchronization required. If a query fails on a storage node, … work, due to the multiple levels of result set reduction. Finally, Shard-Query can automatically partition sets …

Post: Is your MySQL Application having Busy IO by Oracle Measures ?

queries executions. Also lack of parallel query execution makes limits how much IO full table scan queries can consume. If we look at single…performance with multiple MySQL instances on powerful storage. When you move to multiple …whenever you run these instances on single Server or many and as such …

Post: Should we give a MySQL Query Cache a second chance ?

… MySQL 4.0 Query Cache was designed to work with single core systems and …as where this query comes from or what application user triggered such query. Query Cache matching can …query cache for match. Protection from Multiple Misses So you have item invalidated from query cache and there are multiple

Post: Goal driven performance optimization

… time rather than “all queries“. It is surely good all search queries complete in one seconds…etc. For web applications doing processing in a single thread the following simple formula applies wall… using mutliple components (like sphinx and MySQL) or multiple MySQL Servers because in these cases you …

Post: InnoDB Full-text Search in MySQL 5.6: Part 2, The Queries!

… | | 7112 | Download Idaho Tax Forms for Individual or Business Needs | 0.9273209571838379 | | 7113 | Illinois …to create an *InnoDB* table with a single VARCHAR column named “value”. OK, sounds easy …above query to be “+james +peterson arizona” then we might expect to get back multiple

Post: Intro to OLAP

… all MOLAP solutions pre-compute many (or even all) of the possible answers to multi-dimensional queries. Palo is an example of… analysis is constructed. You don’t necessarily have to write queries or drag and drop a report together in order to analyze… includes year, month and quarter. You can create multiple different hierarchies from a single dimension. This allows ‘drill down’ into the dimension…

Post: MySQL Server Memory Usage

… it may be crashing , failing to execute queries or make operation to swap seriously slowing down. … given stage of query is done. Some of them are allocated as single chunk at once … queries. There can be mutiple key caches. Multiple key caches can be created to accomodate query executions Query

Post: MySQL Limitations Part 4: One thread per connection

… a single process with multiple threads. Not all databases are architected this way; some have multiple processes that communicate through shared memory or other… running queries on average. These connections originate from dozens to hundreds of application server instances. When you have a heavily sharded or…. I’m thinking of the lack of sort-merge joins or intra-query parallelism, for example. It would be lovely to have…

Post: Moving Subtrees in Closure Table Hierarchies

…it easy to query for all descendants of A, or all ancestors of D, or many other common queries that are …case of adding a single new node. When you insert a subtree, you’re inserting multiple nodes, and you …DELETE and SELECT from the same table in a single query in MySQL. But we can use MySQL’s multi…