Clustered data sampling

To specify clustered data sampling, set the Sampling type option on the Editor Options (2 of 8) panel to 2. Clustered sampling.

These points describe the behavior of the FM/Db2 editor when using clustered data sampling:
  • Data sampling applies to browse, view, and edit.
  • When using data sampling, the editor always loads all sampled rows into memory. Therefore large table support is NOT available when sampling data.
  • The options that are pertinent to clustered sampling are:
    • Row count on the function entry panel.
    • Start position on the function entry panel.
    • Sampling limit on the Editor Options (2 of 8) panel.
    • Initial skip count on the Editor Options (2 of 8) panel.
    • Include count on the Editor Options (2 of 8) panel.
    • Skip count (final) on the Editor Options (2 of 8) panel.
Behavior of FM/Db2 editor for options related to clustered data sampling describes the behavior of the FM/Db2 editor for various options related to clustered data sampling.
Table 1. Behavior of FM/Db2 editor for options related to clustered data sampling

This table has seven columns, except for the final row, "Note:", which spans all seven columns.
Row count Start position Sampling limit Initial skip count Include count Skip count Behavior
0 1 0 0 nnn 0 All rows sampled
0 1 bbb 0 nnn 0 bbb rows sampled1.
rrr 1 0 0 nnn 0 rrr rows sampled1.
rrr 1 bbb 0 nnn 0 The minimum of (rrr,bbb) rows are sampled1.
0 sss 0 0 nnn 0 Rows sampled from sss until the end of table.
0 sss bbb 0 nnn 0 bbb rows sampled, commencing sss1.
rrr sss 0 0 nnn 0 rrr rows sampled, commencing sss1.
rrr sss bbb 0 nnn 0 The minimum of (rrr,bbb) rows are sampled, commencing sss1.
0 1 0 xxx nnn yyy Rows are sampled in groups of xxx+nnn+yyy rows. Within each group, xxx rows are skipped; nnn rows are sampled and yyy rows are skipped. The first group starts are row 1, the second group at (xxx+nnn+yyy+1). Groups are sampled until the end of the result table1.
0 1 bbb xxx nnn yyy Rows are sampled in groups of xxx+nnn+yyy rows. Within each group, xxx rows are skipped; nnn rows are sampled and yyy rows are skipped. The first group starts are row 1, the second group at (xxx+nnn+yyy+1). Groups are sampled until bbb rows are loaded.1.
rrr 1 0 xxx nnn yyy Rows are sampled in groups of xxx+nnn+yyy rows. Within each group, xxx rows are skipped; nnn rows are sampled and yyy rows are skipped. The first group starts are row 1, the second group at (xxx+nnn+yyy+1). Groups are sampled until rrr rows are loaded1.
rrr 1 bbb xxx nnn yyy Rows are sampled in groups of xxx+nnn+yyy rows. Within each group, xxx rows are skipped; nnn rows are sampled and yyy rows are skipped. The first group starts are row 1, the second group at (xxx+nnn+yyy+1). Groups are sampled until the minimum of (bbb,rrr) rows are loaded1.
rrr sss bbb xxx nnn yyy Rows are sampled in groups of xxx+nnn+yyy rows. Within each group, xxx rows are skipped; nnn rows are sampled and yyy rows are skipped. The first group starts are row sss, the second group at sss+(xxx+nnn+yyy). Groups are sampled until the minimum of (bbb,rrr) rows are loaded1.
Note:
  1. Sampling continues until one of these conditions is met:
    • Any non-zero Sampling limit is reached.
    • Any non-zero Row count limit is reached.
    • The end of the result table is reached.