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JavaScript ModifyPlan.prototype.existsJoin

MarkLogic 12 Product Documentation
op:exists-join

op:exists-join(
   $leftPlan as map:map,
   $rightPlan as map:map,
   [$keys as map:map*],
   [$condition as map:map?]
) as map:map

Summary

This method is a filtering join that filters based on whether the join exists or not but doesn't add any columns.

It filters the left row set to the rows that have a join in the right row set.

Parameters
$leftPlan The row set from the left view.
$rightPlan The row set from the right view.
$keys Equality condition(s) expressed using one or more calls to the function op:on. These conditions are used to compare the left and right rows.
$condition A boolean expression used to compare the left and right rows. See Boolean Expression Functions for the list of functions used to build boolean expressions.

Usage Notes

Both keys and condition are used to specify the join condition. keys allows for a simplified syntax for equality join condition. While condition allows for inequality and complex join conditions. This method combines keys and condition using an AND operator such that: 
      $view
        => op:exists-join (
          $other-view,
          op:on(op:view-col('view', 'column1'), op:view-col('other-view', 'column2')),
          op:ge(op:view-col('view', 'column3'), op:view-col('other-view', 'column4'))
        )
is the same as 
      $view
        => op:exists-join (
          $other-view,
          (),
          op:and(
            op:eq(op:view-col('view', 'column1'), op:view-col('other-view', 'column2')),
            op:ge(op:view-col('view', 'column3'), op:view-col('other-view', 'column4'))
          )
        )

Example

(: It filters out {'r1':1, 'k1':'a'},{'r1':2, 'k1':'a'} in p1 as value 'a' exists in column 'k2' of p2 :)
xquery version "1.0-ml";
import module namespace op="http://marklogic.com/optic"
     at "/MarkLogic/optic.xqy";

let $p1:= op:from-literals((
  map:entry("r1", 1) => map:with("k1", "a"),
  map:entry("r1", 2) => map:with("k1", "a"),
  map:entry("r1", 3) => map:with("k1", "b")
))

let $p2:= op:from-literals((
       map:entry("r2", 3) => map:with("k2", "a"),
       map:entry("r2", 4) => map:with("k2", "c")
     ))
     
return  op:exists-join(
     $p1,$p2,
     op:on("k1", "k2")
   ) => op:result()

Example

(: It filters out {'r1':2, 'k1':'a'} in p1 where r1 equals to 2, as value 'a' exists in column 'k2' of p2 :)
xquery version "1.0-ml";
import module namespace op="http://marklogic.com/optic"
     at "/MarkLogic/optic.xqy";

let $p1:= op:from-literals((
  map:entry("r1", 1) => map:with("k1", "a"),
  map:entry("r1", 2) => map:with("k1", "a"),
  map:entry("r1", 3) => map:with("k1", "b")
))

let $p2:= op:from-literals((
       map:entry("r2", 3) => map:with("k2", "a"),
       map:entry("r2", 4) => map:with("k2", "c")
     ))
     
return  op:exists-join(
     $p1,$p2,
     op:on("k1", "k2"),
     op:eq(op:col("r1"),2)
   ) => op:result()

Example

xquery version "1.0-ml";
 
import module namespace op="http://marklogic.com/optic"
     at "/MarkLogic/optic.xqy";

let $fruits := 
  op:from-literals((
    map:entry("fruit", "mango") => map:with("count", 10),
    map:entry("fruit", "apple") => map:with("count", 7),
    map:entry("fruit", "orange") => map:with("count", 9)
  ))
let $orders :=
  op:from-literals((
    map:entry("flavor", "apple") => map:with("cups", 5),
    map:entry("flavor", "orange") => map:with("cups", 14)
  ))
return $fruits
  => op:exists-join(
    $orders,
    op:on(op:col('fruit'), op:col('flavor')),
    op:ge(op:col('count'), op:col('cups'))
  )
  => op:result()

(: 
  row with fruit of 'apple' will be returned without data from orders
:)

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