# HG changeset patch
# User Timo Sirainen <timo.sirainen@dovecot.fi>
# Date 1476646818 -10800
# Node ID c9e829c8a36fc7485c939b9b8c6a59717fd1b2d5
# Parent  f57ce7cb62eb72d764d6ce2f3caf56f8d4a6051c
lib-dict: Added dict_iterate_set_limit()

diff -r f57ce7cb62eb -r c9e829c8a36f src/lib-dict/dict-private.h
--- a/src/lib-dict/dict-private.h	Mon Oct 17 19:21:34 2016 +0300
+++ b/src/lib-dict/dict-private.h	Sun Oct 16 22:40:18 2016 +0300
@@ -54,6 +54,7 @@
 	void *async_context;
 
 	unsigned int has_more:1;
+	uint64_t row_count, max_rows;
 };
 
 struct dict_transaction_context {
diff -r f57ce7cb62eb -r c9e829c8a36f src/lib-dict/dict.c
--- a/src/lib-dict/dict.c	Mon Oct 17 19:21:34 2016 +0300
+++ b/src/lib-dict/dict.c	Sun Oct 16 22:40:18 2016 +0300
@@ -175,8 +175,16 @@
 bool dict_iterate(struct dict_iterate_context *ctx,
 		  const char **key_r, const char **value_r)
 {
-	return ctx == &dict_iter_unsupported ? FALSE :
-		ctx->dict->v.iterate(ctx, key_r, value_r);
+	if (ctx == &dict_iter_unsupported)
+		return FALSE;
+	if (ctx->max_rows > 0 && ctx->row_count >= ctx->max_rows) {
+		/* row count was limited */
+		return FALSE;
+	}
+	if (!ctx->dict->v.iterate(ctx, key_r, value_r))
+		return FALSE;
+	ctx->row_count++;
+	return TRUE;
 }
 
 void dict_iterate_set_async_callback(struct dict_iterate_context *ctx,
@@ -187,6 +195,12 @@
 	ctx->async_context = context;
 }
 
+void dict_iterate_set_limit(struct dict_iterate_context *ctx,
+			    uint64_t max_rows)
+{
+	ctx->max_rows = max_rows;
+}
+
 bool dict_iterate_has_more(struct dict_iterate_context *ctx)
 {
 	return ctx->has_more;
diff -r f57ce7cb62eb -r c9e829c8a36f src/lib-dict/dict.h
--- a/src/lib-dict/dict.h	Mon Oct 17 19:21:34 2016 +0300
+++ b/src/lib-dict/dict.h	Sun Oct 16 22:40:18 2016 +0300
@@ -107,6 +107,10 @@
 void dict_iterate_set_async_callback(struct dict_iterate_context *ctx,
 				     dict_iterate_callback_t *callback,
 				     void *context);
+/* Limit how many rows will be returned by the iteration (0 = unlimited).
+   This allows backends to optimize the query (e.g. use LIMIT 1 with SQL). */
+void dict_iterate_set_limit(struct dict_iterate_context *ctx,
+			    uint64_t max_rows);
 /* If dict_iterate() returns FALSE, the iteration may be finished or if this
    is an async iteration it may be waiting for more data. If this function
    returns TRUE, the dict callback is called again with more data. */