performance - Java: get data fast: store in memory vs read from file -


iam writing data table generator tool , have performance problems - need care ram usage , time of generating. key in program.

1) need store final data in single file (one file = 1 table, load later when files generated), like:

111|aaaa|bbba 112|aaab|bbbb 113|aaac|bbbc 114|aaad|bbbd...

i have many columns , milion of rows. values correct.

2) now, need generate single value next table using values 1 of genereted table. program can save single column temporary file (to read in future), like:

aaaa aaab aaac aaad...

now, main problem need randomly 'read' new value milion times, same row counter is.

how ? tools use ? have 2 options:

  • store 2nd column 'available values' temporary file in array / arraylist , use eg. .get(int index) method , return value
  • read specific line file , return value

thanks help

how ?

to read file randomly, need know offset of each record. store binary file 4 byte or 8 byte offset start of each line.

you can use library chronicle map allows random read record in file key.


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