#pragma warning disable RCS1163 // Unused parameter.
/// <summary>
/// Alternate common conflict handler, always overwrites changes with new value on conflict.
/// Returns no change if conflict is not due to conflict or data issue.
/// </summary>
/// <param name="ctx">unused</param>
/// <param name="eConflict">reason for callback</param>
/// <param name="pIter">conflict change set, may iterate through values</param>
/// <returns>SQLITE_CHANGESET_REPLACE indicating overwrite with conflicting value</returns>
public static ConflictResolution CallbackReplaceOnConflicts(IntPtr pCtx, ConflictReason eConflict, IntPtr pIter)
#pragma warning restore RCS1163 // Unused parameter.
{
#if false // example code only
object ctx = null;
if (pCtx != IntPtr.Zero)
{
GCHandle gch = GCHandle.FromIntPtr(pCtx);
ctx = gch.Target;
}
var myCtx = ctx as string;
// Note: pIter should be converted to a Sqlite3ChangesetIterator to allow using ChangeSetOp,ChangeSet*Value methods
// however must actually create Sqlite3ConflictChangesetIterator to avoid unnecessary finalize of iterator
var iter = new Sqlite3ConflictChangesetIterator(pIter);
// get table, column, and other information about this change
string table;
int columnCount;
ActionCode op;
bool indirect;
ChangeSetOp(iter, out table, out columnCount, out op, out indirect);
SQLiteValue value;
for (int i = 0; i < columnCount; i++)
{
// on conflict with op=SQLITE_INSERT newvalue is the value to use on REPLACE, conflictvalue is current value (unchanged if omit)
// oldvalue is unused with op=SQLITE_INSERT
if (ChangeSetNewValue(iter, i, out value) == SQLite3.Result.OK)
{
object o = value.GetValue();
}
if (ChangeSetOldValue(iter, i, out value) == SQLite3.Result.OK)
{
object o = value.GetValue();
}
if (ChangeSetConflictValue(iter, i, out value) == SQLite3.Result.OK)
{
object o = value.GetValue();
}
}
#endif
// replace only valid on conflict or data
if ((eConflict == ConflictReason.SQLITE_CHANGESET_CONFLICT) || (eConflict == ConflictReason.SQLITE_CHANGESET_DATA))
{
return(ConflictResolution.SQLITE_CHANGESET_REPLACE);
}
else
{
return(ConflictResolution.SQLITE_CHANGESET_OMIT);
}
}
internal static string FieldsConflictMessage(string responseName, ConflictReason reason) =>
$"Fields {responseName} conflicts because {ReasonMessage(reason.Message)}. " +
"Use different aliases on the fields to fetch both if this was intentional.";
/// <summary>
/// Default conflict handler if null is specified, ignores all conflicts and makes no changes
/// </summary>
/// <param name="ctx">unused</param>
/// <param name="eConflict">reason for callback</param>
/// <param name="iter">conflict change set, may iterate through values</param>
/// <returns>always returns SQLITE_CHANGESET_OMIT</returns>
public static ConflictResolution CallbackIgnoreConflicts(IntPtr pCtx, ConflictReason eConflict, IntPtr iter)
{
return(ConflictResolution.SQLITE_CHANGESET_OMIT);
}
/// <summary>
/// Conflict handler, allows multiple methods of conflict resolution.
/// </summary>
/// <param name="ctx">information about how to handler conflicts per table</param>
/// <param name="eConflict">reason for callback</param>
/// <param name="pIter">conflict change set, may iterate through values</param>
/// <returns>how to respond to conflicting value, leave unchanged, replace, or abort</returns>
public static ConflictResolution CallbackConflictHandler(IntPtr pCtx, ConflictReason eConflict, IntPtr pIter)
{
try
{
// get our context
object ctx = null;
if (pCtx != IntPtr.Zero)
{
System.Runtime.InteropServices.GCHandle gch = System.Runtime.InteropServices.GCHandle.FromIntPtr(pCtx);
ctx = gch.Target;
}
var dbSync = ctx as DBSync;
var dbConnection = dbSync.db;
// Note: pIter should be converted to a Sqlite3ChangesetIterator to allow using ChangeSetOp,ChangeSet*Value methods
// however must actually create Sqlite3ConflictChangesetIterator to avoid unnecessary finalize of iterator
var iter = new Sqlite3ConflictChangesetIterator(pIter);
// get table, column, and other information about this change
ChangeSetOp(iter, out string tableName, out int columnCount, out ActionCode op, out bool indirect);
// get information about columns in current table
var tableInfo = dbSync.tableInformation[tableName];
object currentValue, oldValue, newValue;
// get primary key value for current row - NOTE: we support a single or multiple column PK
var pkValues = SQLiteSession.ChangeSetPrimaryKeyValues(iter);
if (pkValues.Count < 1)
{
// we require a primary key and failed to get it!
return(ConflictResolution.SQLITE_CHANGESET_ABORT);
}
PrimaryKeyData[] pk = new PrimaryKeyData[pkValues.Count];
for (var i = 0; i < pkValues.Count; i++)
{
// get primary key column's value
pk[i].value = pkValues[i].Item1.GetValue();
// get primary key column's name from index for table
pk[i].name = tableInfo[pkValues[i].Item2].Name;
}
// log some debug information about conflict (data to sync)
{
var sb = new StringBuilder($"Conflict ({eConflict}) in table '{tableName}' for pk='{pk}', op={op}, Row values:"); sb.AppendLine();
for (int i = 0; i < tableInfo.Count; i++)
{
GetConflictValues(ref iter, op, i, out currentValue, out oldValue, out newValue);
sb.AppendLine($"[{i}] current={currentValue}, old={oldValue}, new={newValue}");
}
logger.Debug(sb.ToString());
}
// TODO handle constraint violations better
if ((eConflict == ConflictReason.SQLITE_CHANGESET_CONSTRAINT) || (eConflict == ConflictReason.SQLITE_CHANGESET_FOREIGN_KEY))
{
return(ConflictResolution.SQLITE_CHANGESET_ABORT);
}
// if op==insert then in current db and not in replica
// so is this a new record (keep) or a deleted record in replica (do we want to replicate delete?)
// newValue (and currentValue) has current's value including timestamp if available
// oldValue is null, need to query replica's shadow table to see if deleted (and timestamp) or if
// not found then assume a new row (so keep)
//
// if op==delete then in replica db and not in current
// so is this a new record (insert) or a deleted record in current (do we want keep delete?)
// oldValue has the replica's value including timestamp if available
// newValue (and currentValue) are null, need to query current's shadow table to see if deleted (and timestamp) or if
// not found then assume a new row (so insert)
//
// if op==update then which do we keep, current or replica => we can do this per column or per row
// oldValue and newValue are null then column has no conflict (currentValue has column's value)
// oldValue is replica's value, newValue (and currentValue) is current's value
//
// TODO - how to handle constraint and foreign key violations, structuring order of replicating tables
// should avoid these in most cases, for now we punt and abort!
// get timestamps from current and replica row, if have a timestamp (-1 for column if not one)
int timestampColumn = FindColumn(tableInfo, "timestamp");
DateTime?currentTimestamp = null, replicaTimestamp = null;
if (timestampColumn >= 0)
{
GetConflictValues(ref iter, op, timestampColumn, out currentValue, out oldValue, out newValue);
if (op == ActionCode.SQLITE_UPDATE) // both are in conflict values
{
currentTimestamp = currentValue as DateTime?;
replicaTimestamp = (oldValue as DateTime?) ?? currentTimestamp; // no oldValue indicates identical values
}
else // must query a shadow table
{
DateTime?shadowTimestamp = null;
var query = new StringBuilder($"SELECT [del_timestamp] FROM ");
query.Append((op == ActionCode.SQLITE_INSERT) ? "replica" : "main");
query.Append(".");
query.Append(tableName);
query.Append("_ WHERE "); // shadow table has _ suffix, e.g. [MyTable] shadow table is [MyTable_]
var keys = new List <object>(pk.Length);
for (var i = 0; i < pk.Length; i++)
{
if (i != 0)
{
query.Append(" AND ");
}
query.Append(pk[i].name);
query.Append("=?");
keys.Add(pk[i].value);
}
query.Append(";");
try
{
// if no shadow table or not a deleted row then this will throw since doesn't exist
shadowTimestamp = dbConnection.ExecuteScalar <DateTime>(query.ToString(), keys.ToArray());
}
catch (Exception) { /* swallow error if no shadow record */ }
if (op == ActionCode.SQLITE_INSERT)
{
if (currentValue != null)
{
currentTimestamp = new DateTime((long)currentValue);
}
replicaTimestamp = shadowTimestamp;
}
else
{
currentTimestamp = shadowTimestamp;
if (oldValue != null)
{
replicaTimestamp = new DateTime((long)oldValue);
}
}
}
}
// Note: the way we are using Session, we explicitly make the changes
// in all cases except on Update where we currently keep or replace whole row
// TODO allow selection of individual fields? which would require us to manually
// do the update - hence also returning SQLITE_CHANGESET_OMIT
var action = ConflictResolution.SQLITE_CHANGESET_OMIT;
if (op == ActionCode.SQLITE_INSERT)
{
// keep current value unless replicaTimestamp is newer
if ((currentTimestamp != null) && (replicaTimestamp != null) && (currentTimestamp < replicaTimestamp))
{
// TODO - we need to actually issue a DELETE!
// TODO - then update shadow table so del_timestamp matches replica
}
}
else if (op == ActionCode.SQLITE_DELETE)
{
// indicate nothing to do, as we have to manually insert if desired to add
action = ConflictResolution.SQLITE_CHANGESET_OMIT;
// are we a new row only in replica? or was modified in replica after we deleted so re-add modified value?
if ((currentTimestamp == null) ||
((replicaTimestamp != null) && (currentTimestamp < replicaTimestamp)))
{
// then insert it
{
var sb = new StringBuilder("INSERT INTO ");
sb.Append(tableName);
sb.Append(" (");
for (var i = 0; i < tableInfo.Count; i++)
{
if (i != 0)
{
sb.Append(", ");
}
sb.Append("["); // double quoted "column names" are standard, but [name] works and easier to read
sb.Append(tableInfo[i].Name); // if any chance of user driven names then use " and escape internal "s
sb.Append("]");
}
sb.Append(") VALUES (");
var values = new object[tableInfo.Count];
for (var i = 0; i < tableInfo.Count; i++)
{
if (i != 0)
{
sb.Append(", ");
}
sb.Append("?");
oldValue = null;
if (ChangeSetOldValue(iter, i, out SQLiteNetSessionModule.SQLiteValue value) == SQLite3.Result.OK)
{
if (value.HasValue())
{
oldValue = value.GetValue();
}
}
values[i] = oldValue;
}
sb.Append(");");
logger.Debug("Inserting: '{0}' with values={1}", sb.ToString(), statePrinter.PrintObject(values));
dbConnection.Execute(sb.ToString(), values);
}
}
// else assume we deleted on purpose so leave that way
}
else if (op == ActionCode.SQLITE_UPDATE)
{
// TODO allow more fine grained selection - for now simply keep latest change
if ((currentTimestamp == null) || (replicaTimestamp == null) || (currentTimestamp >= replicaTimestamp))
{
action = ConflictResolution.SQLITE_CHANGESET_OMIT;
}
else
{
action = ConflictResolution.SQLITE_CHANGESET_REPLACE;
}
}
else
{
logger.Error($"Unknown or unexpected op {op} - aborting!");
}
// replace only valid on conflict or data
//if ((eConflict == ConflictReason.SQLITE_CHANGESET_CONFLICT) || (eConflict == ConflictReason.SQLITE_CHANGESET_DATA))
logger.Debug($"returning action={action}\r\n");
return(action);
}
catch (Exception e)
{
logger.Error(e, "Unexpected error during conflict handler callback.");
return(ConflictResolution.SQLITE_CHANGESET_ABORT);
}
}
