Documentation
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Overview ¶
Package predicate provides built-in predicates to use with distributed queries.
How Distributed Query Works ¶
1. The requested predicate is sent to each member in the cluster. 2. Each member looks at its own local entries and filters them according to the predicate. At this stage, key-value pairs of the entries are deserialized and then passed to the predicate. 3. The predicate requester merges all the results coming from each member into a single set.
Distributed query is highly scalable. If you add new members to the cluster, the partition count for each member is reduced and thus the time spent by each member on iterating its entries is reduced. In addition, the pool of partition threads evaluates the entries concurrently in each member, and the network traffic is also reduced since only filtered data is sent to the requester.
Index ¶
- func And(predicates ...Predicate) *predAnd
- func Between(attribute string, from interface{}, to interface{}) *predBetween
- func Equal(attributeName string, value interface{}) *predEqual
- func False() *predFalse
- func Greater(attributeName string, value interface{}) *predGreaterLess
- func GreaterOrEqual(attributeName string, value interface{}) *predGreaterLess
- func ILike(attributeName string, pattern string) *predILike
- func In(attributeName string, values ...interface{}) *predIn
- func InstanceOf(className string) *predInstanceOf
- func Less(attributeName string, value interface{}) *predGreaterLess
- func LessOrEqual(attributeName string, value interface{}) *predGreaterLess
- func Like(attributeName string, expression string) *predLike
- func Not(predicate Predicate) *predNot
- func NotEqual(attributeName string, value interface{}) *predNotEqual
- func Or(predicates ...Predicate) *predOr
- func Regex(attributeName string, expression string) *predRegex
- func SQL(expression string) *predSQL
- func True() *predTrue
- type Predicate
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func And ¶
func And(predicates ...Predicate) *predAnd
And creates a predicate that will perform the logical and operation on the given predicates. If no predicate is provided as argument, the created predicate will always evaluate to true.
func Between ¶
func Between(attribute string, from interface{}, to interface{}) *predBetween
Between creates a predicate that will pass items if the value stored under the given item attribute is contained inside the given range.
The bounds are inclusive.
func Equal ¶
func Equal(attributeName string, value interface{}) *predEqual
Equal creates a predicate that will pass items if the given value and the value stored under the given item attribute are equal.
func False ¶
func False() *predFalse
False creates a predicate that always evaluates to false and passes no items.
func Greater ¶
func Greater(attributeName string, value interface{}) *predGreaterLess
Greater creates a predicate that will pass items if the value stored under the given item attribute is greater than the given value.
func GreaterOrEqual ¶
func GreaterOrEqual(attributeName string, value interface{}) *predGreaterLess
GreaterOrEqual creates a predicate that will pass items if the value stored under the given item attribute is greater than or equal to the given value.
func ILike ¶
ILike creates a predicate that will pass items if the given pattern matches the value stored under the given item attribute in a case-insensitive manner.
The % (percentage sign) is a placeholder for multiplecharacters, the _ (underscore) is a placeholder for a single character. If you need to match the percentage sign or the underscore character itself, escape it with the backslash, for example "\\%" string will match the percentage sign.
func In ¶
func In(attributeName string, values ...interface{}) *predIn
In creates a predicate that will pass items if the value stored under the given item attribute is a member of the given values.
func InstanceOf ¶
func InstanceOf(className string) *predInstanceOf
InstanceOf creates a predicate that will pass entries for which the value class is an instance of the given className.
func Less ¶
func Less(attributeName string, value interface{}) *predGreaterLess
Less creates a predicate that will pass items if the value stored under the given item “attribute“ is less than the given value.
func LessOrEqual ¶
func LessOrEqual(attributeName string, value interface{}) *predGreaterLess
LessOrEqual creates a predicate that will pass items if the value stored under the given item attribute is less than or equal to the given value.
func Like ¶
Like creates a predicate that will pass items if the given pattern matches the value stored under the given item attribute in a case-sensitive manner.
The % (percentage sign) is a placeholder for multiplecharacters, the _ (underscore) is a placeholder for a single character. If you need to match the percentage sign or the underscore character itself, escape it with the backslash, for example "\\%" string will match the percentage sign.
func Not ¶
func Not(predicate Predicate) *predNot
Not creates a predicate that will negate the result of the given predicate.
func NotEqual ¶
func NotEqual(attributeName string, value interface{}) *predNotEqual
NotEqual creates a predicate that will pass items if the given value and the value stored under the given item attribute are not equal.
func Or ¶
func Or(predicates ...Predicate) *predOr
Or creates a predicate that will perform the logical or operation on the given predicates.
func Regex ¶
Regex creates a predicate that will pass items if the given pattern matches the value stored under the given item attribute.
The pattern interpreted exactly the same as described in https://docs.oracle.com/javase/8/docs/api/java/util/regex/Pattern.html.
func SQL ¶
func SQL(expression string) *predSQL
SQL creates a predicate that will pass items that match the given SQL where expression.
The following operators are supported: =, <, >, <=, >=, ==, !=, <>, BETWEEN, IN, LIKE, ILIKE, REGEX, AND, OR, NOT.
The operators are case-insensitive, but attribute names are case sensitive.
Example:
active AND (age > 20 OR salary < 60000)
Differences to standard SQL: * We don't use ternary boolean logic. field=10 evaluates to false, if field is null, in standard SQL it evaluates to UNKNOWN. * IS [NOT] NULL is not supported, use =NULL or <>NULL. * IS [NOT] DISTINCT FROM is not supported, but = and <> behave like it.
Types ¶
type Predicate ¶
type Predicate interface {
serialization.IdentifiedDataSerializable
fmt.Stringer
}
Source Files
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- doc.go
- predicate.go
- predicate_and.go
- predicate_between.go
- predicate_equal.go
- predicate_false.go
- predicate_greater.go
- predicate_greater_less.go
- predicate_greater_or_equal.go
- predicate_ilike.go
- predicate_in.go
- predicate_instance_of.go
- predicate_less.go
- predicate_less_or_equal.go
- predicate_like.go
- predicate_not.go
- predicate_not_equal.go
- predicate_or.go
- predicate_regex.go
- predicate_sql.go
- predicate_true.go