Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>Java provides a general-purpose sorting routine which can be used as part of the larger solution to your problem. A common approach to sort data that's too large to all fit in memory is this:</p> <p>1) Read as much data as will fit into main memory, let's say it's 1 Gb</p> <p>2) Quicksort that 1 Gb (here's where you'd use Java's built-in sort from the Collections framework)</p> <p>3) Write that sorted 1 Gb to disk as "chunk-1"</p> <p>4) Repeat steps 1-3 until you've gone through all the data, saving each data chunk in a separate file. So if your original data was 9 Gb, you will now have 9 sorted chunks of data labeled "chunk-1" thru "chunk-9"</p> <p>5) You now just need a final merge sort to merge the 9 sorted chunks into a single fully sorted data set. The merge sort will work very efficiently against these pre-sorted chunks. It will essentially open 9 file readers (one for each chunk), plus one file writer (for output). It then compares the first data element in each read file and selects the smallest value, which is written to the output file. The reader from which that selected value came advances to its next data element, and the 9-way comparison process to find the smallest value is repeated, again writing the answer to the output file. This process repeats until all data has been read from all the chunk files.</p> <p>6) Once step 5 has finished reading all the data you are done -- your output file now contains a fully sorted data set </p> <p>With this approach you could easily write a generic "megasort" utility of your own that takes a filename and maxMemory parameter and efficiently sorts the file by using temp files. I'd bet you could find at least a few implementations out there for this, but if not you can just roll your own as described above.</p>
    singulars
    1. This table or related slice is empty.
    1. POfile based merge sort on large datasets in Java
      singulars
      1. PTQuestion
    1. PTAnswer
    1. This table or related slice is empty.
    1. USMagnus
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POfile based merge sort on large datasets in Java
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI've found an article with this method and including Java code : http://www.codeodor.com/index.cfm/2007/5/10/Sorting-really-BIG-files/1194
      singulars
      1. PO
      1. USFranck
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload