The combined index type and syntax type is called the index strategy. To specify an index, you declare it using a string that specifies your index strategy. This string is formatted as follows:
[unique]-{path type}-{node type}-{key type}-{syntax type}
where:
unique is the actual value that you
provide in this position on the string. If you provide this
value, then indexed values must be unique.
If you do not want indexed values to
be unique, provide nothing for this position in the string.
See Uniqueness for more information.
{path type} identifies the path type. Valid values are:
node
edge
See Path Types for more information.
{node type} identifies the type of node
being indexed. Valid values are:
element
attribute
metadata
If metadata is specified, then {path type} must be
node.
See Node Types for more information.
{key type} identifies the sort of test that the index supports. The following key types are supported:
presence
equality
substring
See Key Types for more information.
{syntax type} identifies the syntax to use for the indexed value. Specify one of the following values:
none
anyURI
base64Binary
boolean
date
dateTime
dayTimeDuration
decimal
double
duration
float
gDay
gMonth
gMonthDay
gYear
gYearMonth
hexBinary
NOTATION
QName
string
time
yearMonthDuration
untypedAtomic
Note that if the key type is presence, then the syntax type should be
none. Also, for queries that examine
numerical data without specifying the cast explicitly,
use double instead
of decimal for the index. This is because the XQuery
specification requires implict casts of numerical data
to be performed as a double.
The following are some example index strategies:
node-element-presence-none
Index an element node for presence queries. That is, queries that test whether the node exists in the document.
unique-node-metadata-equality-string
Index a metadata node for equality string compares. The value provided for this node must be unique within the container.
This strategy is actually used by default for all documents in a container. It is used to index the document's name.
edge-attribute-equality-float
Defines an equality float index for an attribute's edge. Improves performance for queries that examine whether a specific element/@attribute path is equal to a float value.
Also, be aware that you can specify multiple indices at a time by providing a space-separated list of index strategies in the string. For example, you can specify two index strategies at a time using:
"node-element-presence-none edge-attribute-equality-float"