Join filter queries using Intersect and Union

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

@@ -365,19 +365,33 @@ internal fun Search.getQuery(
 
   var filterStatement = ""
   val filterArgs = mutableListOf<Any>()
-  val filterQuery = getFilterQueries()
-  filterQuery.forEachIndexed { i, it ->
-    filterStatement +=
-      //  spotless:off
-      """
-      ${if (i == 0) "AND a.resourceUuid IN (" else "a.resourceUuid IN ("}
-      ${it.query}
-      )
-      ${if (i != filterQuery.lastIndex) "${operation.logicalOperator} " else ""}
-      """.trimIndent()
-    //  spotless:on
-    filterArgs.addAll(it.args)
-  }
+  val nestedSearchQuery = nestedSearches.nestedQuery(type, operation)
+  val filterQuery =
+    getFilterQueries().let {
+      if (nestedSearchQuery != null) {
+        it + nestedSearchQuery
+      } else {
+        it
+      }
+    }
+  val filterJoinOperator =
+    when (operation) {
+      Operation.OR -> "\nUNION\n"
+      Operation.AND -> "\nINTERSECT\n"
+    }
+  filterQuery
+    .takeIf { it.isNotEmpty() }
+    ?.let {
+      filterStatement +=
+        it.joinToString(
+          separator = filterJoinOperator,
+          prefix = "AND a.resourceUuid IN (",
+          postfix = ")\n",
+        ) { fq ->
+          fq.query
+        }
+      filterArgs.addAll(it.flatMap { fq -> fq.args })
+    }
 
   var limitStatement = ""
   val limitArgs = mutableListOf<Any>()
@@ -390,10 +404,6 @@ internal fun Search.getQuery(
     }
   }
 
-  nestedSearches.nestedQuery(type, operation)?.let {
-    filterStatement += it.query
-    filterArgs.addAll(it.args)
-  }
   val whereArgs = mutableListOf<Any>()
   val nestedArgs = mutableListOf<Any>()
   val query =

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

@@ -214,15 +214,20 @@ internal fun List<NestedSearch>.nestedQuery(
   return if (isEmpty()) {
     null
   } else {
+    val filterJoinOperator =
+      when (operation) {
+        Operation.OR -> "\nUNION\n"
+        Operation.AND -> "\nINTERSECT\n"
+      }
+
     map { it.nestedQuery(type) }
       .let { searchQueries ->
         SearchQuery(
           query =
             searchQueries.joinToString(
-              prefix = "AND a.resourceUuid IN ",
-              separator = " ${operation.logicalOperator} a.resourceUuid IN",
+              separator = " $filterJoinOperator",
             ) { searchQuery ->
-              "(\n${searchQuery.query}\n) "
+              "\n${searchQuery.query}\n"
             },
           args = searchQueries.flatMap { it.args },
         )

engine/src/test/java/com/google/android/fhir/search/SearchTest.kt

@@ -1919,8 +1919,7 @@ class SearchTest {
         AND a.resourceUuid IN (
         SELECT resourceUuid FROM StringIndexEntity
         WHERE resourceType = ? AND index_name = ? AND index_value = ?
-        )
-        AND a.resourceUuid IN (
+        INTERSECT
         SELECT resourceUuid
         FROM ResourceEntity a
         WHERE a.resourceType = ? AND a.resourceId IN (
@@ -1930,8 +1929,7 @@ class SearchTest {
         AND a.resourceUuid IN (
         SELECT resourceUuid FROM TokenIndexEntity
         WHERE resourceType = ? AND index_name = ? AND (index_value = ? AND IFNULL(index_system,'') = ?)
-        )
-        AND a.resourceUuid IN (
+        INTERSECT
         SELECT resourceUuid FROM TokenIndexEntity
         WHERE resourceType = ? AND index_name = ? AND (index_value = ? AND IFNULL(index_system,'') = ?)
         )
@@ -2001,7 +1999,7 @@ class SearchTest {
         WHERE resourceType = ? AND index_name = ? AND (index_value = ? AND IFNULL(index_system,'') = ?)
         )
         )
-        )  AND a.resourceUuid IN(
+        INTERSECT
         SELECT resourceUuid
         FROM ResourceEntity a
         WHERE a.resourceType = ? AND a.resourceId IN (
@@ -2156,8 +2154,7 @@ class SearchTest {
         AND a.resourceUuid IN (
         SELECT resourceUuid FROM StringIndexEntity
         WHERE resourceType = ? AND index_name = ? AND index_value = ?
-        )
-        OR a.resourceUuid IN (
+        UNION
         SELECT resourceUuid FROM StringIndexEntity
         WHERE resourceType = ? AND index_name = ? AND index_value = ?
         )
@@ -2189,8 +2186,7 @@ class SearchTest {
         AND a.resourceUuid IN (
         SELECT resourceUuid FROM StringIndexEntity
         WHERE resourceType = ? AND index_name = ? AND index_value LIKE ? || '%' COLLATE NOCASE
-        )
-        AND a.resourceUuid IN (
+        INTERSECT
         SELECT resourceUuid FROM StringIndexEntity
         WHERE resourceType = ? AND index_name = ? AND (index_value LIKE ? || '%' COLLATE NOCASE OR index_value LIKE ? || '%' COLLATE NOCASE)
         )