Embodiments relate to database management. More particularly, embodiments relate to techniques for efficiently tuning database queries.
Traditional database query tuning techniques include, for example, use of statistics to determine a most efficient path and/or use of optimized indexes. Other techniques can also but utilized. However, current techniques can only provide partial improvement. More efficient query optimization is desirable to provide a more efficient database environment.
Embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements.
In the following description, numerous specific details are set forth. However, embodiments of the invention may be practiced without these specific details. In other instances, well-known structures and techniques have not been shown in detail in order not to obscure the understanding of this description.
Various embodiments of tuning recommendation engines are described herein. In one embodiment, tuning recommendations can be utilized via a query plan interface. For example, when using the salesforce cloud environment, the tuning recommendations can be run/managed/accessed via a query plan user interface (e.g., Explain Query Plan page). In alternate embodiments, the tuning recommendations can be invoked separately and/or provides as a background process.
As described in greater detail below, a tuning query recommendation engine can be provided via the query plan user interface in a mode that also considers potential indexes. In one embodiment, potential indexes are the set of all custom indexes and native skinny indexes that could be built on columns that are filtered or sorted on in the query.
In general, an index is a data structure that can be utilized to improve the performance of data retrieval operations on a database table and usually have an associated cost of additional writes and/or storage space utilization to maintain the index. These indexes can provide the ability to locate data without having to search every row of the database each time a database table is accessed. A skinny table generally refers to a database table having a reduced number of columns (e.g., 2 columns, one of which is a primary key).
One or more of the potential indexes are evaluated, 120. In one embodiment, for each potential index, sampled pre-queries are used to estimate the selectivity of the index. In one embodiment, any available optimizations that could be applied to the indexes can be utilized. In one embodiment, if any of the potential index optimizations would perform better than the existing best option based on existing indexes, that potential optimization can be flagged/reserved/saved for recommendation and/or use.
In one embodiment, if one or more of the potential indexes provides an improvement, the potential index can be built (or a recommendation to build the index can be generated). In one embodiment, once built a potential index can be used directly. In one embodiment, an index join involving one or more potential indexes and zero or more existing indexes can be performed. In one embodiment, one or more sort optimizations can be performed. Other optimizations involving one or more potential indexes and zero or more existing indexes can be performed.
In one embodiment, selectivity can be determined by running a sampled query that tests selectivity on a sample set of a fixed size (e.g., 400 rows) and computes the fraction of rows that would be matched using the new index (or combination of indexes) for the potential new optimization. In one embodiment, one or more of the potential indexes can be scored based on the selectivity, 130.
In one embodiment, potential optimizations can be sorted with existing index optimizations to determine the best plan for the query. If a potential index optimization is determined to be the best option, any potential indexes needed for that optimization are recommended to be built. One or more of these recommendations can be provided for use, 140. The query tuning recommendation engine can report the recommended index(es) for a user to evaluate (e.g., via a graphical user interface) and/or may build the recommended index(es) automatically.
In one embodiment, query tuning interface 200 can include one or more of the graphical elements described with respect to
In one embodiment, interface 200 can also provide tables 230 to which the various recommendations apply. In one embodiment, interface 200 can also provide fields 240 to which the various recommendations apply. This can allow the user some insight into which aspects of the query are being tuned with the corresponding recommendation.
In one embodiment, interface 200 provides cardinality 250 and table size 260 for the tables to which the recommendation corresponds. In one embodiment, interface 200 further provides threshold selectivity 270 for the tables to which the recommendation corresponds. In one embodiment, interface 200 can provide index type 280, which can indicate whether the corresponding custom index is active or potential. This can provide a user with the status of the custom index. In one embodiment, create index buttons 290 (or other interface elements) can allow a user to cause creation of the corresponding custom index.
In one embodiment, a timestamp (310), an organization ID (315), a user ID (320), a query statement ID (325) and an elapsed time (330) is provided for each long running query. In one embodiment, a recommended index (340) can be provided for one or more of the long running queries.
In one embodiment, additional information can be provided via interface 300. For example, a query type (350) and/or a primary entity (355). Further, a query ID (360) can be provided. In one embodiment, some or all of the query statement text (365, 370) can be provided. In one embodiment, the request URI (375) and/or the request ID (380) and/or the source database ID (385) can be provided.
In one embodiment, interface 400 provides one or more recommended indexes that can be created and/or applied in response to user input. In one embodiment, interface 400 provides an organization ID (405) and/or an entity ID (410) for each recommended index. In one embodiment, interface 400 also provides the columns (420) to which the corresponding custom index can be applied.
In one embodiment, interface 400 can provide an index type (430), a status (440) and/or a number of times recommended (450) for each corresponding custom index. In one embodiment, interface 400 can provide an elapsed time (460) and/or an estimated time savings (470) for using the corresponding custom index. In one embodiment, one or more of the recommended custom indexes can have a corresponding Create Index button (or other interface component) to allow a user to cause the custom index to be created.
Various embodiments of the techniques described herein can be utilized in an on-demand database service environment. Various embodiments of on-demand database service environments are described in greater detail below.
Environment 510 is an environment in which an on-demand database service exists. User system 512 may be any machine or system that is used by a user to access a database user system. For example, any of user systems 512 can be a handheld computing device, a mobile phone, a laptop computer, a work station, and/or a network of computing devices. As illustrated in herein
An on-demand database service, such as system 516, is a database system that is made available to outside users that do not need to necessarily be concerned with building and/or maintaining the database system, but instead may be available for their use when the users need the database system (e.g., on the demand of the users). Some on-demand database services may store information from one or more tenants stored into tables of a common database image to form a multi-tenant database system (MTS). Accordingly, “on-demand database service 516” and “system 516” will be used interchangeably herein. A database image may include one or more database objects. A relational database management system (RDMS) or the equivalent may execute storage and retrieval of information against the database object(s). Application platform 518 may be a framework that allows the applications of system 516 to run, such as the hardware and/or software, e.g., the operating system. In an embodiment, on-demand database service 516 may include an application platform 518 that enables creation, managing and executing one or more applications developed by the provider of the on-demand database service, users accessing the on-demand database service via user systems 512, or third party application developers accessing the on-demand database service via user systems 512.
The users of user systems 512 may differ in their respective capacities, and the capacity of a particular user system 512 might be entirely determined by permissions (permission levels) for the current user. For example, where a salesperson is using a particular user system 512 to interact with system 516, that user system has the capacities allotted to that salesperson. However, while an administrator is using that user system to interact with system 516, that user system has the capacities allotted to that administrator. In systems with a hierarchical role model, users at one permission level may have access to applications, data, and database information accessible by a lower permission level user, but may not have access to certain applications, database information, and data accessible by a user at a higher permission level. Thus, different users will have different capabilities with regard to accessing and modifying application and database information, depending on a user's security or permission level.
Network 514 is any network or combination of networks of devices that communicate with one another. For example, network 514 can be any one or any combination of a LAN (local area network), WAN (wide area network), telephone network, wireless network, point-to-point network, star network, token ring network, hub network, or other appropriate configuration. As the most common type of computer network in current use is a TCP/IP (Transfer Control Protocol and Internet Protocol) network, such as the global internetwork of networks often referred to as the “Internet” with a capital “I,” that network will be used in many of the examples herein. However, it should be understood that the networks that one or more implementations might use are not so limited, although TCP/IP is a frequently implemented protocol.
User systems 512 might communicate with system 516 using TCP/IP and, at a higher network level, use other common Internet protocols to communicate, such as HTTP, FTP, AFS, WAP, etc. In an example where HTTP is used, user system 512 might include an HTTP client commonly referred to as a “browser” for sending and receiving HTTP messages to and from an HTTP server at system 516. Such an HTTP server might be implemented as the sole network interface between system 516 and network 514, but other techniques might be used as well or instead. In some implementations, the interface between system 516 and network 514 includes load sharing functionality, such as round-robin HTTP request distributors to balance loads and distribute incoming HTTP requests evenly over a plurality of servers. At least as for the users that are accessing that server, each of the plurality of servers has access to the MTS' data; however, other alternative configurations may be used instead.
In one embodiment, system 516, shown in
One arrangement for elements of system 516 is shown in
Several elements in the system shown in
According to one embodiment, each user system 512 and all of its components are operator configurable using applications, such as a browser, including computer code run using a central processing unit such as an Intel Pentium® processor or the like. Similarly, system 516 (and additional instances of an MTS, where more than one is present) and all of their components might be operator configurable using application(s) including computer code to run using a central processing unit such as processor system 517, which may include an Intel Pentium® processor or the like, and/or multiple processor units. A computer program product embodiment includes a machine-readable storage medium (media) having instructions stored thereon/in which can be used to program a computer to perform any of the processes of the embodiments described herein. Computer code for operating and configuring system 516 to intercommunicate and to process webpages, applications and other data and media content as described herein are preferably downloaded and stored on a hard disk, but the entire program code, or portions thereof, may also be stored in any other volatile or non-volatile memory medium or device as is well known, such as a ROM or RAM, or provided on any media capable of storing program code, such as any type of rotating media including floppy disks, optical discs, digital versatile disk (DVD), compact disk (CD), microdrive, and magneto-optical disks, and magnetic or optical cards, nanosystems (including molecular memory ICs), or any type of media or device suitable for storing instructions and/or data. Additionally, the entire program code, or portions thereof, may be transmitted and downloaded from a software source over a transmission medium, e.g., over the Internet, or from another server, as is well known, or transmitted over any other conventional network connection as is well known (e.g., extranet, VPN, LAN, etc.) using any communication medium and protocols (e.g., TCP/IP, HTTP, HTTPS, Ethernet, etc.) as are well known. It will also be appreciated that computer code for implementing embodiments can be implemented in any programming language that can be executed on a client system and/or server or server system such as, for example, C, C++, HTML, any other markup language, Java™, JavaScript, ActiveX, any other scripting language, such as VBScript, and many other programming languages as are well known may be used. (Java™ is a trademark of Sun Microsystems, Inc.).
According to one embodiment, each system 516 is configured to provide webpages, forms, applications, data and media content to user (client) systems 512 to support the access by user systems 512 as tenants of system 516. As such, system 516 provides security mechanisms to keep each tenant's data separate unless the data is shared. If more than one MTS is used, they may be located in close proximity to one another (e.g., in a server farm located in a single building or campus), or they may be distributed at locations remote from one another (e.g., one or more servers located in city A and one or more servers located in city B). As used herein, each MTS could include one or more logically and/or physically connected servers distributed locally or across one or more geographic locations. Additionally, the term “server” is meant to include a computer system, including processing hardware and process space(s), and an associated storage system and database application (e.g., OODBMS or RDBMS) as is well known in the art. It should also be understood that “server system” and “server” are often used interchangeably herein. Similarly, the database object described herein can be implemented as single databases, a distributed database, a collection of distributed databases, a database with redundant online or offline backups or other redundancies, etc., and might include a distributed database or storage network and associated processing intelligence.
User system 512, network 514, system 516, tenant data storage 522, and system data storage 524 were discussed above in
Application platform 518 includes an application setup mechanism 638 that supports application developers' creation and management of applications, which may be saved as metadata into tenant data storage 522 by save routines 636 for execution by subscribers as one or more tenant process spaces 604 managed by tenant management process 610 for example. Invocations to such applications may be coded using PL/SOQL 634 that provides a programming language style interface extension to API 632. A detailed description of some PL/SOQL language embodiments is discussed in commonly owned U.S. Pat. No. 7,730,478 entitled, “Method and System for Allowing Access to Developed Applicants via a Multi-Tenant Database On-Demand Database Service”—issued Jun. 1, 2010 to Craig Weissman, which is incorporated in its entirety herein for all purposes. Invocations to applications may be detected by one or more system processes, which manage retrieving application metadata 616 for the subscriber making the invocation and executing the metadata as an application in a virtual machine.
Each application server 600 may be communicably coupled to database systems, e.g., having access to system data 525 and tenant data 523, via a different network connection. For example, one application server 6001 might be coupled via the network 514 (e.g., the Internet), another application server 600N-1 might be coupled via a direct network link, and another application server 600N might be coupled by yet a different network connection. Transfer Control Protocol and Internet Protocol (TCP/IP) are typical protocols for communicating between application servers 600 and the database system. However, it will be apparent to one skilled in the art that other transport protocols may be used to optimize the system depending on the network interconnect used.
In certain embodiments, each application server 600 is configured to handle requests for any user associated with any organization that is a tenant. Because it is desirable to be able to add and remove application servers from the server pool at any time for any reason, there is preferably no server affinity for a user and/or organization to a specific application server 600. In one embodiment, therefore, an interface system implementing a load balancing function (e.g., an F5 Big-IP load balancer) is communicably coupled between the application servers 600 and the user systems 512 to distribute requests to the application servers 600. In one embodiment, the load balancer uses a least connections algorithm to route user requests to the application servers 600. Other examples of load balancing algorithms, such as round robin and observed response time, also can be used. For example, in certain embodiments, three consecutive requests from the same user could hit three different application servers 600, and three requests from different users could hit the same application server 600. In this manner, system 516 is multi-tenant, wherein system 516 handles storage of, and access to, different objects, data and applications across disparate users and organizations.
As an example of storage, one tenant might be a company that employs a sales force where each salesperson uses system 516 to manage their sales process. Thus, a user might maintain contact data, leads data, customer follow-up data, performance data, goals and progress data, etc., all applicable to that user's personal sales process (e.g., in tenant data storage 522). In an example of a MTS arrangement, since all of the data and the applications to access, view, modify, report, transmit, calculate, etc., can be maintained and accessed by a user system having nothing more than network access, the user can manage his or her sales efforts and cycles from any of many different user systems. For example, if a salesperson is visiting a customer and the customer has Internet access in their lobby, the salesperson can obtain critical updates as to that customer while waiting for the customer to arrive in the lobby.
While each user's data might be separate from other users' data regardless of the employers of each user, some data might be organization-wide data shared or accessible by a plurality of users or all of the users for a given organization that is a tenant. Thus, there might be some data structures managed by system 516 that are allocated at the tenant level while other data structures might be managed at the user level. Because an MTS might support multiple tenants including possible competitors, the MTS should have security protocols that keep data, applications, and application use separate. Also, because many tenants may opt for access to an MTS rather than maintain their own system, redundancy, up-time, and backup are additional functions that may be implemented in the MTS. In addition to user-specific data and tenant specific data, system 516 might also maintain system level data usable by multiple tenants or other data. Such system level data might include industry reports, news, postings, and the like that are sharable among tenants.
In certain embodiments, user systems 512 (which may be client systems) communicate with application servers 600 to request and update system-level and tenant-level data from system 516 that may require sending one or more queries to tenant data storage 522 and/or system data storage 524. System 516 (e.g., an application server 600 in system 516) automatically generates one or more SQL statements (e.g., one or more SQL queries) that are designed to access the desired information. System data storage 524 may generate query plans to access the requested data from the database.
Each database can generally be viewed as a collection of objects, such as a set of logical tables, containing data fitted into predefined categories. A “table” is one representation of a data object, and may be used herein to simplify the conceptual description of objects and custom objects. It should be understood that “table” and “object” may be used interchangeably herein. Each table generally contains one or more data categories logically arranged as columns or fields in a viewable schema. Each row or record of a table contains an instance of data for each category defined by the fields. For example, a CRM database may include a table that describes a customer with fields for basic contact information such as name, address, phone number, fax number, etc. Another table might describe a purchase order, including fields for information such as customer, product, sale price, date, etc. In some multi-tenant database systems, standard entity tables might be provided for use by all tenants. For CRM database applications, such standard entities might include tables for Account, Contact, Lead, and Opportunity data, each containing pre-defined fields. It should be understood that the word “entity” may also be used interchangeably herein with “object” and “table”.
In some multi-tenant database systems, tenants may be allowed to create and store custom objects, or they may be allowed to customize standard entities or objects, for example by creating custom fields for standard objects, including custom index fields. U.S. patent application Ser. No. 10/817,161, filed Apr. 2, 2004, entitled “Custom Entities and Fields in a Multi-Tenant Database System”, and which is hereby incorporated herein by reference, teaches systems and methods for creating custom objects as well as customizing standard objects in a multi-tenant database system. In certain embodiments, for example, all custom entity data rows are stored in a single multi-tenant physical table, which may contain multiple logical tables per organization. It is transparent to customers that their multiple “tables” are in fact stored in one large table or that their data may be stored in the same table as the data of other customers.
Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.
While the invention has been described in terms of several embodiments, those skilled in the art will recognize that the invention is not limited to the embodiments described, but can be practiced with modification and alteration within the spirit and scope of the appended claims. The description is thus to be regarded as illustrative instead of limiting.
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