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CHAPTER 11

Data Storage and Retrieval

11-46 Using Newton Data Storage Objects

internationalized index: cursor methods such as Next and Prev return entries in

the internationally-indexed order.

Queries on Descending Indexes 11

Even though queries and cursors based on descending order indexes work just like

normal queries and cursors, their behavior can seem confusing if you forget that it

is a function of index order. It is always helpful to remember the following points

when working with queries and cursors—especially when using descending indexes:

■ The “beginning” and “end” of a range of index values is a function of index

key order.

■ The cursor navigates entries in index key order.

This section provides examples of the behavior of cursors that use descending

indexes. These examples are based on a soup containing the entries shown in the

following code fragment; although this example uses string values, any kind of

index key value may be sorted in descending order.

{data: "able", …};

{data: "axe", …};

{data: "name", …};

{data: "noun", …};

Soup indexes normally sort string data in ascending alphabetical order; for example,

"able", "axe", "name", "noun". A descending index sorts the same data in

reverse alphabetical order; for example,

"noun", "name", "axe", "able".

Figure 11-6 depicts the reversed ordering that a descending index provides, with

examples of cursor behavior that is a function of index ordering.

Figure 11-6 Cursor operations on descending index

Descending key order

cursor:Reset(); cursor:GoToKey("az"); cursor:GoToKey("a");

Valid subrange

Z "noun" "name" "az" "axe" "able" A

1 2 ... 473 474 475 476 477 478 479 480 481 482 483 ... 941 942

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