[tarantool-patches] [PATCH v3 4/9] sql: rework SQL_FUNC_COUNT flag semantics
Kirill Shcherbatov
kshcherbatov at tarantool.org
Fri Aug 16 16:26:50 MSK 2019
Tarantool's SQL engine generates a different VDBE bytecode
for ..COUNT(*).. and ..COUNT(fieldname).. operations:
the first one produces a lightweight OP_Count operation that uses
native mechanism to report the count of record in index while
the second one pessimistically opens a space read iterator and
uses Count aggregate function.
A helper routine is_simple_count decides whether such
optimisation is correct. It used to use SQL_FUNC_COUNT flag to
mark a dummy (non-functional) function entry with 0 arguments.
This patch changes SQL_FUNC_COUNT semantics: now it is a marker
of any COUNT function, while is_simple_count relies on count
of arguments to distinguish aggregate and non-aggregate
functions.
Needed for #2200, #4113, #2233
---
src/box/sql/sqlInt.h | 3 ++-
src/box/sql/func.c | 4 ++--
src/box/sql/select.c | 4 +++-
3 files changed, 7 insertions(+), 4 deletions(-)
diff --git a/src/box/sql/sqlInt.h b/src/box/sql/sqlInt.h
index 4adb30c5c..bc3c639e6 100644
--- a/src/box/sql/sqlInt.h
+++ b/src/box/sql/sqlInt.h
@@ -1312,7 +1312,8 @@ struct FuncDestructor {
*/
#define SQL_FUNC_LENGTH 0x0040 /* Built-in length() function */
#define SQL_FUNC_TYPEOF 0x0080 /* Built-in typeof() function */
-#define SQL_FUNC_COUNT 0x0100 /* Built-in count(*) aggregate */
+/** Built-in count() function. */
+#define SQL_FUNC_COUNT 0x0100
#define SQL_FUNC_COALESCE 0x0200 /* Built-in coalesce() or ifnull() */
#define SQL_FUNC_UNLIKELY 0x0400 /* Built-in unlikely() function */
#define SQL_FUNC_CONSTANT 0x0800 /* Constant inputs give a constant output */
diff --git a/src/box/sql/func.c b/src/box/sql/func.c
index 6bd2d0cd7..07c019db9 100644
--- a/src/box/sql/func.c
+++ b/src/box/sql/func.c
@@ -1903,9 +1903,9 @@ sqlRegisterBuiltinFunctions(void)
AGGREGATE(avg, 1, 0, 0, sum_step, avgFinalize,
FIELD_TYPE_NUMBER),
AGGREGATE2(count, 0, 0, 0, countStep, countFinalize,
+ SQL_FUNC_COUNT, FIELD_TYPE_INTEGER),
+ AGGREGATE2(count, 1, 0, 0, countStep, countFinalize,
SQL_FUNC_COUNT, FIELD_TYPE_INTEGER),
- AGGREGATE(count, 1, 0, 0, countStep, countFinalize,
- FIELD_TYPE_INTEGER),
AGGREGATE(group_concat, 1, 0, 0, groupConcatStep,
groupConcatFinalize, FIELD_TYPE_STRING),
AGGREGATE(group_concat, 2, 0, 0, groupConcatStep,
diff --git a/src/box/sql/select.c b/src/box/sql/select.c
index c31076694..ddb5de87e 100644
--- a/src/box/sql/select.c
+++ b/src/box/sql/select.c
@@ -4381,7 +4381,9 @@ is_simple_count(struct Select *select, struct AggInfo *agg_info)
return NULL;
if (NEVER(agg_info->nFunc == 0))
return NULL;
- if ((agg_info->aFunc[0].pFunc->funcFlags & SQL_FUNC_COUNT) == 0)
+ if ((agg_info->aFunc->pFunc->funcFlags & SQL_FUNC_COUNT) == 0 ||
+ (agg_info->aFunc->pExpr->x.pList != NULL &&
+ agg_info->aFunc->pExpr->x.pList->nExpr > 0))
return NULL;
if (expr->flags & EP_Distinct)
return NULL;
--
2.22.1
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