Fix foreign key constraint issues with backup restore.

core-util/src/main/java/org/signal/core/util/SqlUtil.kt

@@ -5,6 +5,7 @@ import android.text.TextUtils
 import androidx.annotation.VisibleForTesting
 import androidx.sqlite.db.SupportSQLiteDatabase
 import org.signal.core.util.logging.Log
+import java.lang.Exception
 import java.util.LinkedList
 import java.util.Locale
 import java.util.stream.Collectors
@@ -87,6 +88,27 @@ object SqlUtil {
       }
   }
 
+  /**
+   * Provides a list of all foreign key violations present.
+   * If a [targetTable] is specified, results will be limited to that table specifically.
+   * Otherwise, the check will be performed across all tables.
+   */
+  @JvmStatic
+  @JvmOverloads
+  fun getForeignKeyViolations(db: SupportSQLiteDatabase, targetTable: String? = null): List<ForeignKeyViolation> {
+    val tableString = if (targetTable != null) "($targetTable)" else ""
+
+    return db.query("PRAGMA foreign_key_check$tableString").readToList { cursor ->
+      val table = cursor.requireNonNullString("table")
+      ForeignKeyViolation(
+        table = table,
+        violatingRowId = cursor.requireLongOrNull("rowid"),
+        dependsOnTable = cursor.requireNonNullString("parent"),
+        column = getForeignKeyViolationColumn(db, table, cursor.requireLong("fkid"))
+      )
+    }
+  }
+
   @JvmStatic
   fun isEmpty(db: SupportSQLiteDatabase, table: String): Boolean {
     db.query("SELECT COUNT(*) FROM $table", null).use { cursor ->
@@ -410,6 +432,21 @@ object SqlUtil {
     return Query(query, args.toTypedArray())
   }
 
+  /** Helper that gets the specific column for a foreign key violation */
+  private fun getForeignKeyViolationColumn(db: SupportSQLiteDatabase, table: String, id: Long): String? {
+    try {
+      db.query("PRAGMA foreign_key_list($table)").forEach { cursor ->
+        if (cursor.requireLong("id") == id) {
+          return cursor.requireString("from")
+        }
+      }
+    } catch (e: Exception) {
+      Log.w(TAG, "Failed to find violation details for id: $id")
+    }
+
+    return null
+  }
+
   class Query(val where: String, val whereArgs: Array<String>) {
     infix fun and(other: Query): Query {
       return if (where.isNotEmpty() && other.where.isNotEmpty()) {
@@ -422,6 +459,20 @@ object SqlUtil {
     }
   }
 
+  data class ForeignKeyViolation(
+    /** The table that declared the REFERENCES clause. */
+    val table: String,
+
+    /** The rowId of the message in [table] that violates the constraint. Will not be present if the table has now rowId. */
+    val violatingRowId: Long?,
+
+    /** The table that [table] has a dependency on. */
+    val dependsOnTable: String,
+
+    /** The column from [table] that has the constraint. A separate query needs to be made to get this, so it's best-effor. */
+    val column: String?
+  )
+
   enum class CollectionOperator(val sql: String) {
     IN("IN"),
     NOT_IN("NOT IN")