sql-execution-plan

问题 There is next partitioned table: CREATE TABLE "ERMB_LOG_TEST_BF"."OUT_SMS"( "TRX_ID" NUMBER(19,0) NOT NULL ENABLE, "CREATE_TS" TIMESTAMP (3) DEFAULT systimestamp NOT NULL ENABLE, /* other fields... */ ) PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 STORAGE(BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT) TABLESPACE "ERMB_LOG_TEST_BF" PARTITION BY RANGE ("TRX_ID") INTERVAL (281474976710656) (PARTITION "SYS_P1358" VALUES LESS THAN (59109745109237760) SEGMENT CREATION IMMEDIATE

问题 Can you please help me understand the reason for the performance drop between these statements? For me it seems like in case of D & E he is first joining the address to all subscribers and at the end applies Offset & Limit. Why on earth would he do that? Am I missing something about how Subselects and Offset work together? Shouldn't he first find the right offset and then start executing the subselects? user_id and address_id are primary keys Select A: 15 ms (OK) : select first 200

问题 Can you please help me understand the reason for the performance drop between these statements? For me it seems like in case of D & E he is first joining the address to all subscribers and at the end applies Offset & Limit. Why on earth would he do that? Am I missing something about how Subselects and Offset work together? Shouldn't he first find the right offset and then start executing the subselects? user_id and address_id are primary keys Select A: 15 ms (OK) : select first 200

问题 Now I have a really tricky thing with Oracle execution plans running havoc, when I use a DETERMINISTIC function on the right hand side of the LIKE operator. This is my situation: The Situation I thought it to be wise to execute a query like this (simplified): SELECT [...] FROM customers cust JOIN addresses addr ON addr.cust_id = cust.id WHERE special_char_filter(cust.surname) like special_char_filter(?) And I would bind ? to something like 'Eder%' . Now customers and addresses are very large

问题 I asked PostgreSQL to explain my query. Part of the explanation was: table_name --> Materialize What does materialize do? I'm joining two tables, not views or anything like that. 回答1: A materialize node means the output of whatever is below it in the tree (which can be a scan, or a full set of joins or something like that) is materalized into memory before the upper node is executed. This is usually done when the outer node needs a source that it can re-scan for some reason or other. So in

问题 I have this query, Declare @Prcocessrate float declare @item varchar(20) declare @process varchar(20) declare @branch varchar(20) set @item = 'shirt' set @process = 'kt' set @branch = '1' select @Prcocessrate = ProcessPrice from itemwiseprocessrate where itemname=@Item and Process=@process and branchid=@branch when I run it single handed, the execution plan only shows 3 steps , see for youself.. but I have this procedure sp_newBooking as ALTER PROC sp_newbooking -- other arguements-- AS BEGIN

问题 When I attempt to do something like SELECT Max(ObjectId) FROM Objects; I see that in the explain-plan that this is performed by doing a sort. Now, sorting (which I guess would require something in the complexity of O(nlogn) ) must be much costlier than just scanning each row and remembering the max value (which could be done in O(n) ). Am I missing something here? Is oracle really performing a sort or does the explain-plan just use the description "sort" for describing a simple scan of all

问题 We have a view that is used to lookup a record in a table by clustered index. The view also has a couple of subqueries in the select statement that lookup data in two large tables, also by clustered index. To hugely simplify it would be something like this: SELECT a, (SELECT b FROM tableB where tableB.a=tableA.a) as b (SELECT c FROM tableC where tableC.a=tableA.a) as c FROM tableA Most lookups to [tableB] correctly use a non-clustered index on [tableB] and work very efficiently. However, very

问题 In Oracle (looking at this in Oracle Enterprise Manager) I have a particular SQL Plan Baseline which is set to Enabled = YES. However, I can't get the ACCEPTED = YES to work. According to the documentation, you need ENABLED and ACCEPTED both. I tried to "evolve" the Baseline but OEM complains (via a Report) that it's 1.06 times worse. That's not true though. Also I would like to know how to ensure it does not auto-purge over time and that's it's fixed. Thanks! 回答1: To enable baseline usage,

问题 I have a following table CREATE TABLE `test_series_analysis_data` ( `email` varchar(255) NOT NULL, `mappingId` int(11) NOT NULL, `packageId` varchar(255) NOT NULL, `sectionName` varchar(255) NOT NULL, `createdAt` datetime(3) DEFAULT NULL, `marksObtained` float NOT NULL, `updatedAt` datetime DEFAULT NULL, `testMetaData` longtext, PRIMARY KEY (`email`,`mappingId`,`packageId`,`sectionName`), KEY `rank_index` (`mappingId`,`packageId`,`sectionName`,`marksObtained`), KEY `mapping_package` (