how to print barcode in c# net QUERY OPTIMIZATION in Font

Paint QR Code in Font QUERY OPTIMIZATION

CHAPTER 11 QUERY OPTIMIZATION
Creating QR Code In None
Using Barcode printer for Font Control to generate, create QR Code JIS X 0510 image in Font applications.
www.OnBarcode.com
Painting PDF 417 In None
Using Barcode creation for Font Control to generate, create PDF 417 image in Font applications.
www.OnBarcode.com
SYNOPSIS DBXP_select_command() THD *thd IN the current thread DESCRIPTION This method executes the SELECT command using the query tree and optimizer. RETURN VALUE Success = 0 Failed = 1 */ int DBXP_select_command(THD *thd) { DBUG_ENTER("DBXP_select_command"); DBXP_explain_select_command(thd); DBUG_RETURN(0); } These changes alter the code to call the EXPLAIN command code rather than executing the query. This allows the tests to return a valid result set (the query plan) so that we can test the optimizer without the query execution portion.
Painting EAN-13 In None
Using Barcode encoder for Font Control to generate, create GS1 - 13 image in Font applications.
www.OnBarcode.com
UCC-128 Generator In None
Using Barcode maker for Font Control to generate, create EAN / UCC - 14 image in Font applications.
www.OnBarcode.com
Note I use a function declaration above the DBXP_select_command() method. This allows the code to
Painting Code-128 In None
Using Barcode creation for Font Control to generate, create Code 128 image in Font applications.
www.OnBarcode.com
QR Code 2d Barcode Encoder In None
Using Barcode drawer for Font Control to generate, create QR Code 2d barcode image in Font applications.
www.OnBarcode.com
call forward to the DBXP_explain_select_command() method without using a header file.
Encoding UPC A In None
Using Barcode maker for Font Control to generate, create UPC-A Supplement 5 image in Font applications.
www.OnBarcode.com
Postnet Printer In None
Using Barcode printer for Font Control to generate, create USPS POSTal Numeric Encoding Technique Barcode image in Font applications.
www.OnBarcode.com
There is also a change necessary to the DBXP_explain_select_command() method. You need to add the call to the new optimize methods. This includes the heuristic_optimization() and cost_optimization() methods. I will discuss the heuristic optimization in more detail in the following sections. Listing 11-3 shows the modifications to the EXPLAIN code. Listing 11-3. Modifications to the EXPLAIN Command Code /* Perform EXPLAIN command. SYNOPSIS DBXP_explain_select_command() THD *thd IN the current thread DESCRIPTION This method executes the EXPLAIN SELECT command. RETURN VALUE Success = 0 Failed = 1
QR-Code Printer In Java
Using Barcode maker for Java Control to generate, create QR image in Java applications.
www.OnBarcode.com
QR Code JIS X 0510 Reader In Visual C#
Using Barcode decoder for .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
CHAPTER 11 QUERY OPTIMIZATION
Drawing Barcode In Java
Using Barcode drawer for Android Control to generate, create Barcode image in Android applications.
www.OnBarcode.com
Creating UPC Code In Visual Basic .NET
Using Barcode generator for .NET framework Control to generate, create GS1 - 12 image in Visual Studio .NET applications.
www.OnBarcode.com
*/ int DBXP_explain_select_command(THD *thd) { bool res; select_result *result = thd->lex->result; DBUG_ENTER("DBXP_explain_select_command"); /* Prepare the tables (check access, locks) */ res = check_table_access(thd, SELECT_ACL, thd->lex->query_tables, 0); if (res) DBUG_RETURN(1); res = open_and_lock_tables(thd, thd->lex->query_tables); if (res) DBUG_RETURN(1); /* Create the query tree and optimize it */ Query_tree *qt = build_query_tree(thd, thd->lex, (TABLE_LIST*) thd->lex->select_lex.table_list.first); qt->heuristic_optimization(); qt->cost_optimization(); /* create a field list for returning the query plan */ List<Item> field_list; /* use the protocol class to communicate to client */ Protocol *protocol= thd->protocol; /* write the field to the client */ field_list.push_back(new Item_empty_string("Execution Path",NAME_LEN)); if (protocol->send_fields(&field_list, Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF)) DBUG_RETURN(TRUE); protocol->prepare_for_resend(); /* generate the query plan and send it to client */ show_plan(protocol, qt->root, qt->root, false); send_eof(thd); /* end of file tells client no more data is coming */ /* unlock tables and cleanup memory */ mysql_unlock_read_tables(thd, thd->lock); delete qt; DBUG_RETURN(0); }
Drawing Code 3 Of 9 In None
Using Barcode maker for Software Control to generate, create USS Code 39 image in Software applications.
www.OnBarcode.com
Barcode Maker In Objective-C
Using Barcode printer for iPhone Control to generate, create Barcode image in iPhone applications.
www.OnBarcode.com
CHAPTER 11 QUERY OPTIMIZATION
Scan UCC - 12 In Visual Studio .NET
Using Barcode scanner for Visual Studio .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
ECC200 Generator In Objective-C
Using Barcode encoder for iPad Control to generate, create DataMatrix image in iPad applications.
www.OnBarcode.com
Important MySQL Structures and Classes
Decode UCC - 12 In Visual Basic .NET
Using Barcode reader for Visual Studio .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
QR-Code Generation In None
Using Barcode drawer for Word Control to generate, create Quick Response Code image in Office Word applications.
www.OnBarcode.com
There are a number of key structures and classes in the MySQL source code. You have already seen many of them in the examples thus far. Some of the more important ones are documented in the MySQL Internals manual. Unfortunately, there is no document that lists them all. The following sections describe some of these structures and classes that you will encounter when working with the DBXP query optimizer (and later the query execution code). These include the TABLE structure, the Field class, and a few of the common Item iterators (the Item class is discussed in 3).
Drawing Code 128A In Objective-C
Using Barcode drawer for iPad Control to generate, create ANSI/AIM Code 128 image in iPad applications.
www.OnBarcode.com
Recognizing Barcode In Java
Using Barcode decoder for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
TABLE Structure
The most important MySQL structure that you will work with when writing the optimizer is the TABLE structure. This structure is defined in /sql/table.h called st_table. It is redefined in /sql/handler.h as TABLE. Most of the MySQL source code refers to the structure as TABLE. This structure is important because it contains all of the pertinent data for a table. It contains everything from a pointer to the appropriate storage handler class to a list of the fields, keys, and temporary buffers for storing rows while executing the query. While the structure is immense (like most important structures in MySQL), there are a few key attributes that you will see over and over again. Table 11-1 lists some of the more important attributes for the TABLE structure. For a detailed examination of the TABLE structure, see the handler.h file.
Table 11-1. TABLE Structure Overview
Attribute
file field fields table_name real_name path record[] reclength rec_buff_length keys next prev
Description
A reference to the storage engine object. An array of fields for the table. The number of fields in the field array. The name of the table. This could be the alias or actual (real) name. Depends on how it was referenced in the query statement. The actual name of the table (not the alias). The location of the .frm file for the table. Two buffers used to store rows from the table during query execution. The total length of the record (in bytes). The length of the record buffers. The number of keys specified for the table. A pointer to the next table in a list of tables. A pointer to the previous table in a list of tables.
Copyright © OnBarcode.com . All rights reserved.