[Tarantool-patches] [PATCH v2 10/15] sql: rework COUNT()

[Mergen Imeev via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

This patch does some refactoring for the SQL built-in aggregate function
COUNT().

Part of #4145
---
 src/box/sql/func.c | 64 +++++++++++++++++++---------------------------
 1 file changed, 26 insertions(+), 38 deletions(-)

diff --git a/src/box/sql/func.c b/src/box/sql/func.c
index b5f154fb1..113df423a 100644
--- a/src/box/sql/func.c
+++ b/src/box/sql/func.c
@@ -150,6 +150,29 @@ fin_avg(struct sql_context *ctx)
 		ctx->is_aborted = true;
 }
 
+/** Implementation of the COUNT() function. */
+static void
+step_count(struct sql_context *ctx, int argc, struct Mem **argv)
+{
+	assert(argc == 0 || argc == 1);
+	if (ctx->pMem->type == MEM_TYPE_NULL)
+		mem_set_uint(ctx->pMem, 0);
+	if (argc == 1 && argv[0]->type == MEM_TYPE_NULL)
+		return;
+	assert(ctx->pMem->type == MEM_TYPE_UINT);
+	++ctx->pMem->u.u;
+}
+
+/** Finalizer for the COUNT() function. */
+static void
+fin_count(struct sql_context *ctx)
+{
+	assert(ctx->pMem->type == MEM_TYPE_NULL || mem_is_uint(ctx->pMem));
+	if (ctx->pMem->type == MEM_TYPE_NULL)
+		return mem_set_uint(ctx->pOut, 0);
+	mem_copy_as_ephemeral(ctx->pOut, ctx->pMem);
+}
+
 static const unsigned char *
 mem_as_ustr(struct Mem *mem)
 {
@@ -1704,41 +1727,6 @@ soundexFunc(sql_context * context, int argc, sql_value ** argv)
 	}
 }
 
-/*
- * The following structure keeps track of state information for the
- * count() aggregate function.
- */
-typedef struct CountCtx CountCtx;
-struct CountCtx {
-	i64 n;
-};
-
-/*
- * Routines to implement the count() aggregate function.
- */
-static void
-countStep(sql_context * context, int argc, sql_value ** argv)
-{
-	CountCtx *p;
-	if (argc != 0 && argc != 1) {
-		diag_set(ClientError, ER_FUNC_WRONG_ARG_COUNT,
-			 "COUNT", "0 or 1", argc);
-		context->is_aborted = true;
-		return;
-	}
-	p = sql_aggregate_context(context, sizeof(*p));
-	if ((argc == 0 || !mem_is_null(argv[0])) && p != NULL)
-		p->n++;
-}
-
-static void
-countFinalize(sql_context * context)
-{
-	CountCtx *p;
-	p = sql_aggregate_context(context, 0);
-	sql_result_uint(context, p ? p->n : 0);
-}
-
 /*
  * Routines to implement min() and max() aggregate functions.
  */
@@ -2008,9 +1996,9 @@ static struct sql_func_definition definitions[] = {
 	 NULL},
 	{"COALESCE", -1, {FIELD_TYPE_ANY}, FIELD_TYPE_SCALAR, sql_builtin_stub,
 	 NULL},
-	{"COUNT", 0, {}, FIELD_TYPE_INTEGER, countStep, countFinalize},
-	{"COUNT", 1, {FIELD_TYPE_ANY}, FIELD_TYPE_INTEGER, countStep,
-	 countFinalize},
+	{"COUNT", 0, {}, FIELD_TYPE_INTEGER, step_count, fin_count},
+	{"COUNT", 1, {FIELD_TYPE_ANY}, FIELD_TYPE_INTEGER, step_count,
+	 fin_count},
 
 	{"GREATEST", -1, {FIELD_TYPE_INTEGER}, FIELD_TYPE_INTEGER, minmaxFunc,
 	 NULL},
-- 
2.25.1