Modify toQueryString to prevent SQLite expression tree from exceeding depth of 1000

engine/src/main/java/com/google/android/fhir/search/filter/FilterCriterion.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2021-2023 Google LLC
+ * Copyright 2021-2024 Google LLC
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -85,16 +85,23 @@ internal sealed class FilterCriteria(
    * This function takes care of wrapping the conditions in brackets so that they are evaluated as
    * intended.
    */
-  private fun List<ConditionParam<*>>.toQueryString(operation: Operation) =
-    this.joinToString(
-      separator = " ${operation.logicalOperator} ",
-      prefix = if (size > 1) "(" else "",
-      postfix = if (size > 1) ")" else "",
-    ) {
-      if (it.params.size > 1) {
-        "(${it.condition})"
-      } else {
-        it.condition
-      }
+  private fun List<ConditionParam<*>>.toQueryString(operation: Operation): String {
+    if (this.size <= 1) {
+      val queryString =
+        firstOrNull()?.let {
+          if (it.params.size > 1) {
+            "(${it.condition})"
+          } else {
+            it.condition
+          }
+        }
+      return queryString ?: ""
     }
+
+    val mid = this.size / 2
+    val left = this.subList(0, mid).toQueryString(operation)
+    val right = this.subList(mid, this.size).toQueryString(operation)
+
+    return "($left ${operation.logicalOperator} $right)"
+  }
 }

engine/src/test/java/com/google/android/fhir/impl/FhirEngineImplTest.kt

@@ -17,6 +17,7 @@
 package com.google.android.fhir.impl
 
 import androidx.test.core.app.ApplicationProvider
+import ca.uhn.fhir.rest.gclient.TokenClientParam
 import ca.uhn.fhir.rest.param.ParamPrefixEnum
 import com.google.android.fhir.FhirServices.Companion.builder
 import com.google.android.fhir.LocalChange
@@ -26,6 +27,8 @@ import com.google.android.fhir.get
 import com.google.android.fhir.lastUpdated
 import com.google.android.fhir.logicalId
 import com.google.android.fhir.search.LOCAL_LAST_UPDATED_PARAM
+import com.google.android.fhir.search.filter.TokenParamFilterCriterion
+import com.google.android.fhir.search.getQuery
 import com.google.android.fhir.search.search
 import com.google.android.fhir.sync.AcceptLocalConflictResolver
 import com.google.android.fhir.sync.AcceptRemoteConflictResolver
@@ -723,6 +726,47 @@ class FhirEngineImplTest {
     assertThat(result.map { it.resource.logicalId }).containsExactly("patient-id-create").inOrder()
   }
 
+  @Test
+  fun `testing search many`() = runTest {
+    val patient1 = Patient().apply { id = "patient-1" }
+    val patient2 = Patient().apply { id = "patient-2" }
+    val patient3 = Patient().apply { id = "patient-45" }
+    val patient4 = Patient().apply { id = "patient-4355" }
+    val patient5 = Patient().apply { id = "patient-899" }
+    val patient6 = Patient().apply { id = "patient-883376" }
+    fhirEngine.create(patient1, patient2, patient3, patient4, patient5, patient6)
+
+    val result1 =
+      fhirEngine.search<Patient> {
+        filter(TokenClientParam("_id"), { value = of(patient3.logicalId) })
+      }
+    assertThat(result1).isNotEmpty()
+    assertThat(result1.size).isEqualTo(1)
+
+    val filterValues =
+      listOf(patient2, patient3, patient1, patient5, patient4, patient6).map<
+        Patient,
+        TokenParamFilterCriterion.() -> Unit,
+      > {
+        { value = of(it.logicalId) }
+      }
+    val result2 =
+      fhirEngine.search<Patient> {
+        filter(TokenClientParam("_id"), *filterValues.toTypedArray())
+        println(getQuery().query)
+        println(getQuery().args)
+      }
+    assertThat(result2.map { it.resource.logicalId })
+      .containsExactly(
+        "patient-2",
+        "patient-45",
+        "patient-1",
+        "patient-4355",
+        "patient-899",
+        "patient-883376",
+      )
+  }
+
   @Test
   fun `update should allow patient search with LOCAL_LAST_UPDATED_PARAM and update local entity`() =
     runBlocking {