Adds support for FILTER in Eval

partiql-eval/src/main/kotlin/org/partiql/eval/internal/Compiler.kt

@@ -1,6 +1,7 @@
 package org.partiql.eval.internal
 
 import org.partiql.eval.internal.operator.Operator
+import org.partiql.eval.internal.operator.rel.RelFilter
 import org.partiql.eval.internal.operator.rel.RelProject
 import org.partiql.eval.internal.operator.rel.RelScan
 import org.partiql.eval.internal.operator.rex.ExprCollection
@@ -69,6 +70,12 @@ internal object Compiler {
             return super.visitRelOp(node.op, ctx) as Operator.Relation
         }
 
+        override fun visitRelOpFilter(node: Rel.Op.Filter, ctx: Unit): Operator {
+            val input = visitRel(node.input, ctx)
+            val condition = visitRex(node.predicate, ctx)
+            return RelFilter(input, condition)
+        }
+
         override fun visitRex(node: Rex, ctx: Unit): Operator.Expr {
             return super.visitRexOp(node.op, ctx) as Operator.Expr
         }

partiql-eval/src/main/kotlin/org/partiql/eval/internal/operator/rel/RelFilter.kt

@@ -0,0 +1,37 @@
+package org.partiql.eval.internal.operator.rel
+
+import org.partiql.eval.internal.Record
+import org.partiql.eval.internal.operator.Operator
+import org.partiql.value.BoolValue
+import org.partiql.value.PartiQLValueExperimental
+
+internal class RelFilter(
+    val input: Operator.Relation,
+    val expr: Operator.Expr
+) : Operator.Relation {
+
+    override fun open() {
+        input.open()
+    }
+
+    override fun next(): Record? {
+        var inputRecord: Record? = input.next()
+        while (inputRecord != null) {
+            if (conditionIsTrue(inputRecord, expr)) {
+                return inputRecord
+            }
+            inputRecord = input.next()
+        }
+        return null
+    }
+
+    override fun close() {
+        input.close()
+    }
+
+    @OptIn(PartiQLValueExperimental::class)
+    private fun conditionIsTrue(record: Record, expr: Operator.Expr): Boolean {
+        val condition = expr.eval(record)
+        return condition is BoolValue && condition.value == true
+    }
+}

partiql-eval/src/test/kotlin/org/partiql/eval/impl/PartiQLEngineDefaultTest.kt → partiql-eval/src/test/kotlin/org/partiql/eval/internal/PartiQLEngineDefaultTest.kt

@@ -1,4 +1,4 @@
-package org.partiql.eval.impl
+package org.partiql.eval.internal
 
 import org.junit.jupiter.api.Test
 import org.partiql.eval.PartiQLEngine
@@ -9,9 +9,13 @@ import org.partiql.planner.PartiQLPlannerBuilder
 import org.partiql.value.BagValue
 import org.partiql.value.PartiQLValueExperimental
 import org.partiql.value.bagValue
+import org.partiql.value.boolValue
 import org.partiql.value.int32Value
 import kotlin.test.assertEquals
 
+/**
+ * This holds sanity tests during the development of the [PartiQLEngine.default] implementation.
+ */
 class PartiQLEngineDefaultTest {
 
     private val engine = PartiQLEngine.default()
@@ -47,4 +51,19 @@ class PartiQLEngineDefaultTest {
         val expected = bagValue(sequenceOf(int32Value(10), int32Value(20), int32Value(30)))
         assertEquals(expected, output)
     }
+
+    @OptIn(PartiQLValueExperimental::class)
+    @Test
+    fun testFilter() {
+        val statement = parser.parse("SELECT VALUE t FROM <<true, false, true, false, false, false>> AS t WHERE t;").root
+        val session = PartiQLPlanner.Session("q", "u")
+        val plan = planner.plan(statement, session)
+
+        val prepared = engine.prepare(plan.plan)
+        val result = engine.execute(prepared) as PartiQLResult.Value
+        val output = result.value as BagValue<*>
+
+        val expected = bagValue(sequenceOf(boolValue(true), boolValue(true)))
+        assertEquals(expected, output)
+    }
 }