.NET/ASP.NET/C#/VB.NET PDF Document SDK

Tip Programming with fewer side effects is attractive for many reasons. For example, eliminating unnecessary side effects nearly always reduces the complexity of your code, so it leads to fewer bugs. Another thing experienced functional programmers appreciate is that the programmer or compiler can easily adjust the order in which expressions are computed. A lack of side effects also helps you reason about your code: it is easier to visually check when two programs are equivalent, and it is easier to make quite radical adjustments to your code without introducing new, subtle bugs. Programs that are free from side effects can often be computed on demand where necessary, often by making very small, local changes to your code to introduce the use of delayed data structures. Finally, side effects such as mutation are difficult to use when data is accessed concurrently from multiple threads, as you ll see in 14.

barcode format in excel 2007, barcode excel 2013 free, excel barcode schriftart, barcode in excel formula, convert text to barcode in excel 2003, download free barcode generator excel, active barcode excel 2007 download, excel barcode erstellen freeware, free barcode addin for excel 2010, excel2010 microsoft barcode control 9.0,

We create three identical tables t1, t2, and t3 each with one number column x, which is also the primary key: benchmark@ORA10G> create table t1 ( x number primary key); Table created benchmark@ORA10G> create table t2 ( x number primary key); Table created benchmark@ORA10G> create table t3 ( x number primary key); Table created Now we insert 500,000 records into t1 and analyze it to compute statistics for the Oracle optimizer to use: benchmark@ORA10G> insert into t1 select rownum from all_objects, all_users where rownum <= 500000; 500000 rows created We gather statistics for table t1 for the Cost Based Optimizer (CBO) to use next: benchmark@ORA10G> begin 2 dbms_statsgather_table_stats( 3 ownname => 'BENCHMARK', 4 tabname => 'T1', 5 cascade => true ); 6 end; 7 / PL/SQL procedure successfully completed benchmark@ORA10G> commit; Commit complete Now we need to copy the data in this table to another table.

512 512 512 1024 1024

Three looping constructs are available to help make writing iterative code with side effects simple: Simple for loops: for var = start-expr to end-expr do expr done Simple while loops: while expr do expr done Sequence loops: for pattern in expr do expr done All three constructs are for writing imperative programs, indicated partly by the fact that in all cases the body of the loop must have a return type of unit. Note that unit is the F# type that corresponds to void in imperative languages such as C, and it has the single value (). We now cover these three constructs in more detail.

We will look at a PL/SQL solution and a SQL solution The PL/SQL solution copies table t1 s data into table t2 by inserting each row separately:.

Note The done token is optional when using the #light lightweight syntax option (the body of the loop

benchmark@ORA10G> -- pl/sql solution benchmark@ORA10G> declare 2 begin 3 for i in ( select x from t1 ) 4 loop 5 insert into t2 values ( i.x ); 6 end loop; 7 end; 8 / PL/SQL procedure successfully completed. benchmark@ORA10G> commit; The SQL solution simply uses an insert into select clause to directly perform the insert into t3 with one statement: benchmark@ORA10G> -- sql solution benchmark@ORA10G> insert into t3 2 select x 3 from t1; 38988 rows created. We use the runstats utility to do the comparison as follows. The code begins with marking the start point of a benchmark run by invoking runstats_pkg.rs_start: benchmark@ORA10G> exec runstats_pkg.rs_start; We first invoke our SQL-based solution: benchmark@ORA10G> -- sql solution benchmark@ORA10G> insert into t3 2 select x 3 from t1; 38988 rows created. benchmark@ORA10G> commit; We mark the middle of the benchmark run and follow it up with the PL/SQL solution. Finally, we invoke runstats_pkg.rs_stop to display the results: benchmark@ORA10G> exec runstats_pkg.rs_middle; PL/SQL procedure successfully completed. benchmark@ORA10G> -- pl/sql solution benchmark@ORA10G> declare 2 begin

Message Limit (In Bits)

must be indented on a new line).

3 4 5 6 7 8

264 2 2 2

for i in ( select x from t1 ) loop insert into t2 values ( i.x ); end loop; end; /

Simple for loops are the most efficient way to iterate over integer ranges. This is illustrated here by a replacement implementation of the repeatFetch function from 2: let repeatFetch url n = for i = 1 to n do let html = http url printf "fetched <<< %s >>>\n" html printf "Done!\n"

PL/SQL procedure successfully completed. benchmark@ORA10G> commit; Commit complete. benchmark@ORA10G> exec runstats_pkg.rs_stop( 50 ); Run1 ran in 5180 hsecs Run2 ran in 5572 hsecs run 1 ran in 92.96% of the time Name STAT...IMU undo allocation siz <-trimmed to save space --> STAT...table scan rows gotten Run1 52 500,940 Run2 0 3,699,690 Diff -52 3,198,750