KeywordsStable

trait KeywordsStable extends AnyRef

Keywords to mark aggregate expressions on and unifications of attributes.

// Aggregates on any attribute type
Person.age(count).get.map(_.head ==> 3)         // count of asserted `age` attribute values
Person.age(countDistinct).get.map(_.head ==> 3) // count of asserted distinct `age` attribute values
Person.age(max).get.map(_.head ==> 38)          // maximum `age` value (using `compare`)
Person.age(min).get.map(_.head ==> 5)           // maximum `age` value (using `compare`)
Person.age(sample).get.map(_.head ==> 27)       // single sample `age` value

// Aggregates on any attribute type, returning multiple values
Person.age(distinct).get.map(_.head ==> Vector(5, 7, 38)) // distinct `age` values
Person.age(max(2)).get.map(_.head ==> Vector(38, 7))      // 2 maximum `age` values
Person.age(min(2)).get.map(_.head ==> Vector(5, 7))       // 2 minimum `age` values
Person.age(sample(2)).get.map(_.head ==> Vector(7, 38))   // 2 sample `age` values

// Aggregates on number attributes
Person.age(sum).get.map(_.head ==> 50)                  // sum of all `age` numbers
Person.age(avg).get.map(_.head ==> 16.66666667)         // average of all `age` numbers
Person.age(median).get.map(_.head ==> 7)                // median of all `age` numbers
Person.age(stddev).get.map(_.head ==> 15.107025591499)  // standard deviation of all `age` numbers
Person.age(variance).get.map(_.head ==> 228.2222222222) // variance of all `age` numbers

Source: Keywords.scala

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trait AggrCoalesce extends AggrKw
trait AggrInt extends AggrKw
trait AggrKw extends Kw
trait Kw extends AnyRef
trait avg extends AggrCoalesce
Average of attribute values.
Average of attribute values.

Apply avg keyword to attribute to return average of attribute values of entities matching the molecule.
```
for {
  _ <- Match.sKeywords.insert(1, 2, 4)
  _ <- Match.score(avg).get.map(_.head ==> 2.3333333333333335) // (1 + 2 + 4) / 3
} yield ()
```
returns
Double
trait bi extends AnyRef

trait count extends AggrCoalesce with AggrInt

Count of attribute values.

Count of attribute values.

Apply count keyword to attribute to return count of attribute values of entities matching the molecule.

for {
  _ <- Person.firstName.lastName.age insert List(
    ("Ben", "Hayday", 42),
    ("Liz", "Taylor", 34),
    ("Liz", "Swifty", 34),
    ("Liz", "Mooray", 25)
  )
  _ <- Person.firstName.age(count).get.map(_ ==> List(
    ("Ben", 1),
    ("Liz", 3) // 34, 34, 25
  ))
} yield ()

returns: Int

trait countDistinct extends AggrCoalesce

Count of distinct attribute values.

Count of distinct attribute values.

Apply countDistinct keyword to attribute to return count of distinct attribute values of entities matching the molecule.

for {
  _ <- Person.firstName.lastName.age insert List(
    ("Ben", "Hayday", 42),
    ("Liz", "Taylor", 34),
    ("Liz", "Swifty", 34),
    ("Liz", "Mooray", 25)
  )
  _ <- Person.firstName.age(countDistinct).get.map(_ ==> List(
    ("Ben", 1),
    ("Liz", 2) // 34, 25
  ))
} yield ()

returns: Int

trait distinct extends AggrKw

Distinct attribute values.

Distinct attribute values.

Apply distinct keyword to attribute to return Vector of distinct attribute values of entities matching the molecule.

for {
  _ <- Person.firstName.lastName.age insert List(
    ("Ben", "Hayday", 42),
    ("Liz", "Taylor", 34),
    ("Liz", "Swifty", 34),
    ("Liz", "Mooray", 25)
  )
  _ <- Person.firstName.age(distinct) insert List(
    ("Ben", 42),
    ("Liz", Vector(34, 25)) // only single 34 returned
  )
} yield ()

returns: List[attribute-type]

trait max extends AggrKw
Maximum attribute value(s).
Maximum attribute value(s).

Apply max keyword to attribute to return the maximum attribute value of entities matching the molecule.
```
for {
  _ <- Person.age.insert(25, 34, 37, 42, 70)
  _ <- Person.age(max).get.map(_.head ==> 70)
} yield ()
```
Apply max(n) to return Vector of the n biggest values.
```
Person.age(max(3)).get.map(_.head ==> Vector(37, 42, 70))
```
Note
max/max(n) supports all value types (via comparators).
max(n) Can at most return the number of values that match.
case class maxs(n: Int) extends Kw with Product with Serializable
trait median extends AggrCoalesce
Median of attribute values.
Median of attribute values.

Apply median keyword to attribute to return median of attribute values of entities matching the molecule.
```
for {
  _ <- Match.sKeywords.insert(1, 2, 4)
  _ <- Match.score(median).get.map(_.head ==> 2)
} yield ()
```
OBS: When it comes to an even number of values, Datomic has a special implementation of median that is different from the one described on the Wiki entry on the median function.

Datomic calculates the median of even number of values as the average of the two middle numbers rounded down to nearest whole number
```
for {
  _ <- Match.sKeywords.insert(1, 2, 3, 4)
  _ <- Match.score(median).get.map(_.head ==> 2) // (2 + 3) / 2 = 2.5 rounded down to 2
} yield ()
```
With decimal numbers this can go wrong:
```
for {
  _ <- Match.sKeywords.insert(1.0, 2.5, 2.5, 3.0)
  _ <- Match.score(median).get.map(_.head ==> 2) // (2.5 + 2.5) / 2 = 2.5 rounded down to 2 (This is wrong and bug report has been filed)
} yield ()
```
returns
Value of Attribute type
trait min extends AggrKw
Minimum attribute value(s).
Minimum attribute value(s).

Apply min keyword to attribute to return the minimum attribute value of entities matching the molecule.
```
for {
  _ <- Person.age.insert(25, 34, 37, 42, 70)
  _ <- Person.age(min).get.map(_.head ==> 25)
} yield ()
```
Apply min(n) to return Vector of the n smallest values.
```
Person.age(min(3)).get.map(_.head ==> Vector(25, 34, 37))
```
Note
min/min(n) supports all value types (via comparators).
min(n) Can at most return the number of values that match.
case class mins(n: Int) extends Kw with Product with Serializable
trait sample extends AggrKw
Sample attribute value(s).
Sample attribute value(s).

Apply sample keyword to attribute to return a single sample (random) attribute value of entities matching the molecule.
```
for {
  _ <- Person.age.insert(25, 34, 37, 42, 70)
  _ <- Person.age(sample).get.map(_.head ==> 42) // or other..
} yield ()
```
Apply sample(n) to return Vector of up to n distinct sample values.
```
Person.age(sample(3)).get.map(_.head ==> Vector(70, 25, 37)) // or other..
```
Note
Can at most return the number of values that match.
case class samples(n: Int) extends Kw with Product with Serializable
trait stddev extends AggrCoalesce
Variance of attribute values.
Variance of attribute values.

Apply stddev keyword to attribute to return variance of attribute values of entities matching the molecule.
```
for {
  _ <- Match.sKeywords.insert(1, 2, 4)
  _ <- Match.score(stddev).get.map(_.head ==> 1.247219128924647)
} yield ()
```
returns
Double
trait sum extends AggrCoalesce
Sum of attribute values.
Sum of attribute values.

Apply sum keyword to attribute to return sum of attribute values of entities matching the molecule.
```
for {
  _ <- Match.sKeywords.insert(1, 2, 4)
  _ <- Match.score(sum).get.map(_.head ==> 7)
} yield ()
```
returns
Value of Attribute type

trait unify extends Kw

Unify attribute value in self-join.

Unify attribute value in self-join.

Apply unify marker to attribute to unify its value with previous values of the same attribute in the molecule in a self-join.

for {
  _ <- m(Person.age.name.Beverages * Beverage.name.rating) insert List(
    (23, "Joe", List(("Coffee", 3), ("Cola", 2), ("Pepsi", 3))),
    (25, "Ben", List(("Coffee", 2), ("Tea", 3))),
    (23, "Liz", List(("Coffee", 1), ("Tea", 3), ("Pepsi", 1))))

  // What beverages do pairs of 23- AND 25-year-olds like in common?
  // Drink name is unified - Joe and Ben both drink coffee, etc..
  _ <- Person.age_(23).name.Beverages.name._Ns.Self
      .age_(25).name.Beverages.name_(unify).get.map(_.sorted ==> List(
    ("Joe", "Coffee", "Ben"),
    ("Liz", "Coffee", "Ben"),
    ("Liz", "Tea", "Ben")
  ))
} yield ()

trait v1 extends Kw
trait variance extends AggrCoalesce
Variance of attribute values.
Variance of attribute values.

Apply variance keyword to attribute to return variance of attribute values of entities matching the molecule.
```
for {
  _ <- Match.sKeywords.insert(1, 2, 4)
  _ <- Match.score(variance).get.map(_.head ==> 1.5555555555555556)
} yield ()
```
returns
Double

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KeywordsStable

trait KeywordsStable extends AnyRef

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trait KeywordsStable extends AnyRef

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KeywordsStable