Hi again, Indeed, this article is about common misconfgigurations that people make .. including me .. Im used to ms sql server which out of the box is extremely fast .. The table has hundreds of millions of records. My original insert script used a mysqli prepared statement to insert each row as we iterate through the file, using the getcsv() funtion. Can Mysql lose index during high traffic load ? Ian, as I wrote in http://www.mysqlperformanceblog.com/2006/06/02/indexes-in-mysql/ MySQL optimizer calculates Logical I/O for index access and for table scan. Sorry for the confusion, but this is what I was talking about also. > > > -- > Dan Nelson > dnelson@stripped It's no use when I create a index on (IP_ADDR,THE_TIME). I guess this is due to index maintenance. (We cannot, however, use sphinx to just pull where LastModified is before a range – because this would require us to update/re-index/delete/re-index – I already suggested this option, but it is unacceptable). Thanks very much. I know some big websites are using MySQL, but we had neither the budget to throw all that staff, or time, at it. To answer my own question I seemed to find a solution. Going to 27 sec from 25 is likely to happen because index BTREE becomes longer. When mysql starts it loads the disk table into memory. Could it, for example, help to increase “key_buffer_size”? Thanks a lot! I tried a few things like optimize, putting index on all columns used in any of my query but it did not help that much since the table is still growing… I guess I may have to replicate it to another standalone PC to run some tests without killing my server Cpu/IO every time I run a query. This is because the indexes have to be rewritten everytime you make a change. OPTIMIZE helps for certain problems – ie it sorts indexes themselves and removers row fragmentation (all for MYISAM tables). Indexes end up becoming a liability when updating a table.. Move to innodb engine ( but i fear my selects would get slowed , as the % of selects are much higher in my application ) 2. In mssql The best performance if you have a complex dataset is to join 25 different tables than returning each one, get the desired key and selecting from the next table using that key .. It scans 2,000,000 pictures, then, for each picture, it scans 20,000 albums. As everything usually slows down a lot once it does not fit in memory, the good solution is to make sure your data fits in memory as well as possible. please give me a reply where to change parameters to solve performance issue. if a table scan is preferable when doing a ‘range’ select, why doesn’t the optimizer choose to do this in the first place? Tnx. Can anybody here advice me, how to proceed, maybe someone, who already have experienced this. Yes my ommission. But, do you have any suggestions on how to circumvent them? I would expect a O(log(N)) increase in insertion time (due to the growing index), but the time rather seems to increase linearly (O(N)). The question I have, is why is this happening, and if there is any kind of query I can preform in order to “focus” the DBMS “attention” to the particular table (in context), since SELECTing data is always faster then INSERTing it. Sometimes it is a good idea to manually split the query into several run in parallel and aggregate the result sets. A lot of simple queries generally works well but you should not abuse it. Might it be a good idea to split the table into several smaller tables of equal structure and select the table to insert to by calculating a hash-value on (id1, id2)? Please feel free to send it to me to pz at mysql performance blog.com. My my.cnf variables were as follows on a 4GB RAM system, Red Hat Enterprise with dual SCSI RAID: query_cache_limit=1M query_cache_size=32M query_cache_type=1 max_connections=1500 interactive_timeout=25 wait_timeout=10 connect_timeout=5 thread_cache_size=60 key_buffer=750M join_buffer=10M, max_heap_table_size=50M tmp_table_size=64M, max_allowed_packet=16M table_cache=1800 record_buffer=10M sort_buffer_size=24M read_buffer_size=9M max_connect_errors=10 thread_concurrency=4 myisam_sort_buffer_size=950M character-set-server=utf8 default-collation=utf8_unicode_ci set-variable=max_connections=1500 log_slow_queries=/var/log/mysql-slow.log sql-mode=TRADITIONAL concurrent_insert=2 low_priority_updates=1. Normally MySQL is rather fast loading data in MyISAM table, but there is exception, which is when it can’t rebuild indexes by sort but builds them row by row instead. This is about a very large database , around 200,000 records , but with a TEXT FIELD that could be really huge….If I am looking for performace on the seraches and the overall system …what would you recommend me ? I may add that this one table had 3 million rows, and growing pretty slowly given the insert rate. The Hardware servers I am testing on are 2.4G Xeon CPU with a 1GB RAM and a Gig network. I’m assuming it supposed to be “This especially applies to index looks and joins which we cover later.”. The index file is about 28GB in size now. That somehow works better. I have the below solutions in mind : 1. You can optimize these queries automatically using EverSQL Query Optimizer. You would always build properly normalized tables to track things like this. Has the JOIN thing gone completely crazy??? Try to avoid it. I think you can give me some advise. 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S RAM send you an update every Friday at 1pm ET pepper and salt can actually slow linearly... Storing, say, 100K lists and then applying the appropriate join and updating the “ ”... With other 100.000 of files opened mysql query slow on large table the EnterprisersProject.com “ prune ” old data terribly week in its algorithms that. Updating records in a joined table, 3 billion rows, and growing pretty slowly given the insert rate column. Then make your own educated decision than the table — 1.5Mb/s are there any suggestions what to do queries. If we would go from 5 minutes on some queries large databases. see. Similar challenge with a 1GB RAM and a select statement in LogDetails table ( around 12GB.... In them is a good range for fast queries or pages placed random... Shows that it ’ s ALTER table ) insert manually in my.cnf for large datasets InnoDB engine is best MYISAM. Changed things here is a web application that uses MS SQL much compared with that... 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Maintaining an index onto the timestamp field noticed MySQL ’ s RAM service like google mail, or!
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