Hi,
Massive pattern list handling with -E format seems very
slow, since grep 2.28.
Conversion from -E format to -F format may have problem
about performance.
When the processing time is measured by the script below,
the result isobviously different between 2.28 and 2.27.
----
#!/bin/bash
export LC_ALL=C
rm -f grep-patterns.txt
for i in {1..2000}; do
pat=$(echo -n "$i" | sha1sum | cut -f1 -d ' ')
echo -e "$pat$pat(\$|$pat)" >> grep-patterns.txt
done
echo executing grep...
time grep -E -v -m1 -f grep-patterns.txt /dev/null
----
The following is the results in my PC with fedora's RPM.
https://koji.fedoraproject.org/koji/packageinfo?packageID=1023
- result with grep 2.28
real 0m11.087s / user 0m11.027s / sys 0m0.037s
- result with grep 2.27
real 0m0.144s / user 0m0.116s / sys 0m0.027s
With also recent 3.4, result is same.
I hope you find it useful.
regards,
