using mapfile is extreamly slow compared to oldfashinod ways to read files

[Lennart Schultz]

Configuration Information [Automatically generated, do not change]:
Machine: i686
OS: linux-gnu
Compiler: i686-pc-linux-gnu-gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i686'
-DCONF_OSTYPE='linu
x-gnu' -DCONF_MACHTYPE='i686-pc-linux-gnu' -DCONF_VENDOR='pc'
-DLOCALEDIR='/usr/
share/locale' -DPACKAGE='bash' -DSHELL -DHAVE_CONFIG_H   -I.  -I.
-I./include -I
./lib
-DDEFAULT_PATH_VALUE='/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/
sbin:/bin' -DSTANDARD_UTILS_PATH='/bin:/usr/bin:/sbin:/usr/sbin'
-DSYS_BASHRC='/
etc/bash/bashrc' -DSYS_BASH_LOGOUT='/etc/bash/bash_logout'
-DNON_INTERACTIVE_LOG
IN_SHELLS -DSSH_SOURCE_BASHRC -march=athlon-xp -O2 -pipe
-fomit-frame-pointer -g
3
uname output: Linux dragoda.com 2.6.28-gentoo-r2 #1 SMP Sat Feb 28 19:17:31
CET
2009 i686 AMD Sempron(tm) 3000+ AuthenticAMD GNU/Linux
Machine Type: i686-pc-linux-gnu

Bash Version: 4.0
Patch Level: 10
Release Status: release

Description:

I have a bash script which reads about 250000 lines of xml code generating
about 850 files with information extracted from the xml file.
It uses the construct:

while read line
do
   case "$line" in
   ....
done < file

and this takes a little less than 2 minutes

Trying to use mapfile I changed the above construct to:

mapfile  < file
for i in "${MAPFILE[@]}"
do
   line=$(echo $i) # strip leading blanks
   case "$line" in
   ....
done

With this change the job now takes more than 48 minutes. :(

It may be that I am new to mapfiles, and there are more efficient ways to
traverse a mapfile array, but if this the case please document it.

Another suggestion for mapfile:
please introduce an option to strip leading blanks so mapfile acts like
readline so constructions like:
line=$(echo $i) # strip leading blanks
above can be avoid.

-- 
Regards,
Lennart Schultz