public static void DeleteFrom(Parse parse, SrcList tabList, Expr where_)
{
AuthContext sContext = new AuthContext(); // Authorization context
Context ctx = parse.Ctx; // Main database structure
if (parse.Errs != 0 || ctx.MallocFailed)
goto delete_from_cleanup;
Debug.Assert(tabList.Srcs == 1);
// Locate the table which we want to delete. This table has to be put in an SrcList structure because some of the subroutines we
// will be calling are designed to work with multiple tables and expect an SrcList* parameter instead of just a Table* parameter.
Table table = SrcList.Lookup(parse, tabList); // The table from which records will be deleted
if (table == null) goto delete_from_cleanup;
// Figure out if we have any triggers and if the table being deleted from is a view
#if !OMIT_TRIGGER
int dummy;
Trigger trigger = Triggers.Exist(parse, table, TK.DELETE, null, out dummy); // List of table triggers, if required
#if OMIT_VIEW
const bool isView = false;
#else
bool isView = (table.Select != null); // True if attempting to delete from a view
#endif
#else
const Trigger trigger = null;
bool isView = false;
#endif
// If pTab is really a view, make sure it has been initialized.
if (sqlite3ViewGetColumnNames(parse, table) != null || IsReadOnly(parse, table, (trigger != null)))
goto delete_from_cleanup;
int db = sqlite3SchemaToIndex(ctx, table.Schema); // Database number
Debug.Assert(db < ctx.DBs.length);
string dbName = ctx.DBs[db].Name; // Name of database holding pTab
ARC rcauth = Auth.Check(parse, AUTH.DELETE, table.Name, 0, dbName); // Value returned by authorization callback
Debug.Assert(rcauth == ARC.OK || rcauth == ARC.DENY || rcauth == ARC.IGNORE);
if (rcauth == ARC.DENY)
goto delete_from_cleanup;
Debug.Assert(!isView || trigger != null);
// Assign cursor number to the table and all its indices.
Debug.Assert(tabList.Srcs == 1);
int curId = tabList.Ids[0].Cursor = parse.Tabs++; // VDBE VdbeCursor number for pTab
Index idx; // For looping over indices of the table
for (idx = table.Index; idx != null; idx = idx.Next)
parse.Tabs++;
// Start the view context
if (isView)
Auth.ContextPush(parse, sContext, table.Name);
// Begin generating code.
Vdbe v = parse.GetVdbe(); // The virtual database engine
if (v == null)
goto delete_from_cleanup;
if (parse.Nested == 0) v.CountChanges();
parse.BeginWriteOperation(1, db);
// If we are trying to delete from a view, realize that view into a ephemeral table.
#if !OMIT_VIEW && !OMIT_TRIGGER
if (isView)
MaterializeView(parse, table, where_, curId);
#endif
// Resolve the column names in the WHERE clause.
NameContext sNC = new NameContext(); // Name context to resolve expressions in
sNC.Parse = parse;
sNC.SrcList = tabList;
if (sqlite3ResolveExprNames(sNC, ref where_) != 0)
goto delete_from_cleanup;
// Initialize the counter of the number of rows deleted, if we are counting rows.
int memCnt = -1; // Memory cell used for change counting
if ((ctx.Flags & Context.FLAG.CountRows) != 0)
{
memCnt = ++parse.Mems;
v.AddOp2(OP.Integer, 0, memCnt);
}
#if !OMIT_TRUNCATE_OPTIMIZATION
// Special case: A DELETE without a WHERE clause deletes everything. It is easier just to erase the whole table. Prior to version 3.6.5,
// this optimization caused the row change count (the value returned by API function sqlite3_count_changes) to be set incorrectly.
if (rcauth == ARC.OK && where_ == null && trigger == null && !IsVirtual(table) && !FKey.FkRequired(parse, table, null, 0))
{
Debug.Assert(!isView);
v.AddOp4(OP.Clear, table.Id, db, memCnt, table.Name, Vdbe.P4T.STATIC);
for (idx = table.Index; idx != null; idx = idx.Next)
{
Debug.Assert(idx.Schema == table.Schema);
v.AddOp2(OP.Clear, idx.Id, db);
}
}
else
#endif
// The usual case: There is a WHERE clause so we have to scan through the table and pick which records to delete.
{
int rowSet = ++parse.Mems; // Register for rowset of rows to delete
int rowid = ++parse.Mems; // Used for storing rowid values.
// Collect rowids of every row to be deleted.
v.AddOp2(OP.Null, 0, rowSet);
ExprList dummy = null;
WhereInfo winfo = Where.Begin(parse, tabList, where_, ref dummy, WHERE_DUPLICATES_OK, 0); // Information about the WHERE clause
if (winfo == null) goto delete_from_cleanup;
int regRowid = Expr.CodeGetColumn(parse, table, -1, curId, rowid); // Actual register containing rowids
v.AddOp2(OP.RowSetAdd, rowSet, regRowid);
if ((ctx.Flags & Context.FLAG.CountRows) != 0)
v.AddOp2(OP.AddImm, memCnt, 1);
Where.End(winfo);
// Delete every item whose key was written to the list during the database scan. We have to delete items after the scan is complete
// because deleting an item can change the scan order.
int end = v.MakeLabel();
// Unless this is a view, open cursors for the table we are deleting from and all its indices. If this is a view, then the
// only effect this statement has is to fire the INSTEAD OF triggers.
if (!isView)
sqlite3OpenTableAndIndices(parse, table, curId, OP.OpenWrite);
int addr = v.AddOp3(OP.RowSetRead, rowSet, end, rowid);
// Delete the row
#if !OMIT_VIRTUALTABLE
if (IsVirtual(table))
{
VTable vtable = VTable.GetVTable(ctx, table);
VTable.MakeWritable(parse, table);
v.AddOp4(OP.VUpdate, 0, 1, rowid, vtable, Vdbe.P4T.VTAB);
v.ChangeP5(OE.Abort);
sqlite3MayAbort(parse);
}
else
#endif
{
int count = (parse.Nested == 0; // True to count changes
GenerateRowDelete(parse, table, curId, rowid, count, trigger, OE.Default);
}
// End of the delete loop
v.AddOp2(OP.Goto, 0, addr);
v.ResolveLabel(end);
// Close the cursors open on the table and its indexes.
if (!isView && !IsVirtual(table))
{
for (int i = 1, idx = table.Index; idx != null; i++, idx = idx.Next)
v.AddOp2(OP.Close, curId + i, idx.Id);
v.AddOp1(OP.Close, curId);
}
}
// Update the sqlite_sequence table by storing the content of the maximum rowid counter values recorded while inserting into
// autoincrement tables.
if (parse.Nested == 0 && parse.TriggerTab == null)
sqlite3AutoincrementEnd(parse);
// Return the number of rows that were deleted. If this routine is generating code because of a call to sqlite3NestedParse(), do not
// invoke the callback function.
if ((ctx.Flags & Context.FLAG.CountRows) != 0 && parse.Nested == 0 && parse.TriggerTab == null)
{
v.AddOp2(OP.ResultRow, memCnt, 1);
v.SetNumCols(1);
v.SetColName(0, COLNAME_NAME, "rows deleted", SQLITE_STATIC);
}
delete_from_cleanup:
Auth.ContextPop(sContext);
SrcList.Delete(ctx, ref tabList);
Expr.Delete(ctx, ref where_);
return;
}
