[Tarantool-patches] [PATCH v2 3/4] sql: introduce mem_cmp_scalar()

Mergen Imeev imeevma at tarantool.org
Sun Jul 11 20:51:10 MSK 2021


Hi! Thank you for the review! My answers, diff and new patch below.

On Sun, Jul 11, 2021 at 05:03:34PM +0200, Vladislav Shpilevoy wrote:
> Hi! Thanks for the patch!
> 
> See 3 comments below.
> 
> > diff --git a/src/box/sql/func.c b/src/box/sql/func.c
> > index aa565277c..dc99bd390 100644
> > --- a/src/box/sql/func.c
> > +++ b/src/box/sql/func.c
> > @@ -144,11 +144,10 @@ minmaxFunc(sql_context * context, int argc, sql_value ** argv)
> >  	for (i = 1; i < argc; i++) {
> >  		if (mem_is_null(argv[i]))
> >  			return;
> > -		if ((sqlMemCompare(argv[iBest], argv[i], pColl) ^ mask) >=
> > -		    0) {
> > -			testcase(mask == 0);
> > +		int res;
> > +		mem_cmp_scalar(argv[iBest], argv[i], &res, pColl);
> > +		if ((res ^ mask) >= 0)
> 
> 1. It seems that under certain conditions if cmp_scalar fails, res remains
> not initialized. Which can lead to behaviour changing from run to run. The
> same in the other places below.
> 
Fixed, added checks. Also, I believe there shoudn't be any problem when we
compare two values of the same type. Right now all comparison functions can
return -1 when they were given wrong argument, but I believe I will fix this
when I remove implicit cast. I want them to accept only values of predefined
types and return result of comparison. Then we can get rid of unnecessary
checks.

> > diff --git a/src/box/sql/mem.c b/src/box/sql/mem.c
> > index 2595e2fd4..576596c9f 100644
> > --- a/src/box/sql/mem.c
> > +++ b/src/box/sql/mem.c
> > @@ -59,6 +59,40 @@ enum {
> >  	BUF_SIZE = 32,
> >  };
> >  
> > +enum mem_class {
> > +	MEM_CLASS_NULL,
> > +	MEM_CLASS_BOOL,
> > +	MEM_CLASS_NUMBER,
> > +	MEM_CLASS_STR,
> > +	MEM_CLASS_BIN,
> > +	MEM_CLASS_UUID,
> > +	mem_class_max,
> > +};
> 
> 2. It might make sense to add a comment that these must be sorted
> exactly like enum mp_class.
> 
Added.

> > +
> > +static inline enum mem_class
> > +mem_type_class(enum mem_type type)
> > +{
> > +	switch (type) {
> > +	case MEM_TYPE_NULL:
> > +		return MEM_CLASS_NULL;
> > +	case MEM_TYPE_UINT:
> > +	case MEM_TYPE_INT:
> > +	case MEM_TYPE_DOUBLE:
> > +		return MEM_CLASS_NUMBER;
> > +	case MEM_TYPE_STR:
> > +		return MEM_CLASS_STR;
> > +	case MEM_TYPE_BIN:
> > +		return MEM_CLASS_BIN;
> > +	case MEM_TYPE_BOOL:
> > +		return MEM_CLASS_BOOL;
> > +	case MEM_TYPE_UUID:
> > +		return MEM_CLASS_UUID;
> 
> 3. It might work faster without branching if done like
> 'static enum mp_class mp_classes[]' - would allow to take
> the class for any type as simple as an array access
> operation.
This cannot be done directly in current design since value in enum mem_type are
not sequential numbers. However, this can be done using something like this:

diff --git a/src/box/sql/mem.c b/src/box/sql/mem.c
index 4062ff4b3..05a3fb699 100644
--- a/src/box/sql/mem.c
+++ b/src/box/sql/mem.c
@@ -73,28 +73,27 @@ enum mem_class {
 	mem_class_max,
 };
 
+enum mem_class mem_classes[] = {
+	/** MEM_TYPE_NULL	 = */ MEM_CLASS_NULL,
+	/** MEM_TYPE_UINT	 = */ MEM_CLASS_NUMBER,
+	/** MEM_TYPE_INT	 = */ MEM_CLASS_NUMBER,
+	/** MEM_TYPE_STR	 = */ MEM_CLASS_STR,
+	/** MEM_TYPE_BIN	 = */ MEM_CLASS_BIN,
+	/** MEM_TYPE_ARRAY	 = */ mem_class_max,
+	/** MEM_TYPE_MAP	 = */ mem_class_max,
+	/** MEM_TYPE_BOOL	 = */ MEM_CLASS_BOOL,
+	/** MEM_TYPE_DOUBLE	 = */ MEM_CLASS_NUMBER,
+	/** MEM_TYPE_UUID	 = */ MEM_CLASS_UUID,
+	/** MEM_TYPE_INVALID	 = */ mem_class_max,
+	/** MEM_TYPE_FRAME	 = */ mem_class_max,
+	/** MEM_TYPE_PTR	 = */ mem_class_max,
+	/** MEM_TYPE_AGG	 = */ mem_class_max,
+};
+
 static inline enum mem_class
 mem_type_class(enum mem_type type)
 {
-	switch (type) {
-	case MEM_TYPE_NULL:
-		return MEM_CLASS_NULL;
-	case MEM_TYPE_UINT:
-	case MEM_TYPE_INT:
-	case MEM_TYPE_DOUBLE:
-		return MEM_CLASS_NUMBER;
-	case MEM_TYPE_STR:
-		return MEM_CLASS_STR;
-	case MEM_TYPE_BIN:
-		return MEM_CLASS_BIN;
-	case MEM_TYPE_BOOL:
-		return MEM_CLASS_BOOL;
-	case MEM_TYPE_UUID:
-		return MEM_CLASS_UUID;
-	default:
-		break;
-	}
-	return mem_class_max;
+	return mem_classes[ffs(type) - 1];
 }
 
 bool

We can use macro instead of static inline function. What do you think?

Also we can think of way to solve this problem using bit-wise operations,
but it looks too complicated.



Diff:

diff --git a/src/box/sql/func.c b/src/box/sql/func.c
index dc99bd390..efb14f23e 100644
--- a/src/box/sql/func.c
+++ b/src/box/sql/func.c
@@ -145,7 +145,13 @@ minmaxFunc(sql_context * context, int argc, sql_value ** argv)
 		if (mem_is_null(argv[i]))
 			return;
 		int res;
-		mem_cmp_scalar(argv[iBest], argv[i], &res, pColl);
+		if (mem_cmp_scalar(argv[iBest], argv[i], &res, pColl) != 0) {
+			diag_set(ClientError, ER_SQL_TYPE_MISMATCH,
+				 mem_str(argv[i]),
+				 mem_type_to_str(argv[iBest]));
+			context->is_aborted = true;
+			return;
+		}
 		if ((res ^ mask) >= 0)
 			iBest = i;
 	}
@@ -1057,7 +1063,12 @@ nullifFunc(sql_context * context, int NotUsed, sql_value ** argv)
 	struct coll *pColl = sqlGetFuncCollSeq(context);
 	UNUSED_PARAMETER(NotUsed);
 	int res;
-	mem_cmp_scalar(argv[0], argv[1], &res, pColl);
+	if (mem_cmp_scalar(argv[0], argv[1], &res, pColl) != 0) {
+		diag_set(ClientError, ER_SQL_TYPE_MISMATCH,
+			 mem_str(argv[1]), mem_type_to_str(argv[0]));
+		context->is_aborted = true;
+		return;
+	}
 	if (res != 0)
 		sql_result_value(context, argv[0]);
 }
@@ -1827,7 +1838,12 @@ minmaxStep(sql_context * context, int NotUsed, sql_value ** argv)
 		 * comparison is inverted.
 		 */
 		bool is_max = (func->flags & SQL_FUNC_MAX) != 0;
-		mem_cmp_scalar(pBest, pArg, &cmp, pColl);
+		if (mem_cmp_scalar(pBest, pArg, &cmp, pColl) != 0) {
+			diag_set(ClientError, ER_SQL_TYPE_MISMATCH,
+				 mem_str(pArg), mem_type_to_str(pBest));
+			context->is_aborted = true;
+			return;
+		}
 		if ((is_max && cmp < 0) || (!is_max && cmp > 0)) {
 			mem_copy(pBest, pArg);
 		} else {
diff --git a/src/box/sql/mem.c b/src/box/sql/mem.c
index 576596c9f..da27cd191 100644
--- a/src/box/sql/mem.c
+++ b/src/box/sql/mem.c
@@ -59,6 +59,10 @@ enum {
 	BUF_SIZE = 32,
 };
 
+/**
+ * Analogue of enum mp_class for enum mp_type. The order of the classes must be
+ * the same as in the enum mp_class.
+ */
 enum mem_class {
 	MEM_CLASS_NULL,
 	MEM_CLASS_BOOL,



New patch:


commit c65ccc80c55501035ac6d5ab71b0e30460aee0fd
Author: Mergen Imeev <imeevma at gmail.com>
Date:   Sat Jul 10 13:56:39 2021 +0300

    sql: introduce mem_cmp_scalar()
    
    This patch introduces the mem_cmp_scalar() function that compares two
    MEMs using SCALAR rules. MEMs must be scalars. Prior to this patch, there was a
    function that used SCALAR rules to compare two MEMs, but its design became
    overly complex as new types appeared.
    
    Part of #6164

diff --git a/src/box/sql/func.c b/src/box/sql/func.c
index aa565277c..efb14f23e 100644
--- a/src/box/sql/func.c
+++ b/src/box/sql/func.c
@@ -144,11 +144,16 @@ minmaxFunc(sql_context * context, int argc, sql_value ** argv)
 	for (i = 1; i < argc; i++) {
 		if (mem_is_null(argv[i]))
 			return;
-		if ((sqlMemCompare(argv[iBest], argv[i], pColl) ^ mask) >=
-		    0) {
-			testcase(mask == 0);
-			iBest = i;
+		int res;
+		if (mem_cmp_scalar(argv[iBest], argv[i], &res, pColl) != 0) {
+			diag_set(ClientError, ER_SQL_TYPE_MISMATCH,
+				 mem_str(argv[i]),
+				 mem_type_to_str(argv[iBest]));
+			context->is_aborted = true;
+			return;
 		}
+		if ((res ^ mask) >= 0)
+			iBest = i;
 	}
 	sql_result_value(context, argv[iBest]);
 }
@@ -1057,9 +1062,15 @@ nullifFunc(sql_context * context, int NotUsed, sql_value ** argv)
 {
 	struct coll *pColl = sqlGetFuncCollSeq(context);
 	UNUSED_PARAMETER(NotUsed);
-	if (sqlMemCompare(argv[0], argv[1], pColl) != 0) {
-		sql_result_value(context, argv[0]);
+	int res;
+	if (mem_cmp_scalar(argv[0], argv[1], &res, pColl) != 0) {
+		diag_set(ClientError, ER_SQL_TYPE_MISMATCH,
+			 mem_str(argv[1]), mem_type_to_str(argv[0]));
+		context->is_aborted = true;
+		return;
 	}
+	if (res != 0)
+		sql_result_value(context, argv[0]);
 }
 
 /**
@@ -1827,7 +1838,12 @@ minmaxStep(sql_context * context, int NotUsed, sql_value ** argv)
 		 * comparison is inverted.
 		 */
 		bool is_max = (func->flags & SQL_FUNC_MAX) != 0;
-		cmp = sqlMemCompare(pBest, pArg, pColl);
+		if (mem_cmp_scalar(pBest, pArg, &cmp, pColl) != 0) {
+			diag_set(ClientError, ER_SQL_TYPE_MISMATCH,
+				 mem_str(pArg), mem_type_to_str(pBest));
+			context->is_aborted = true;
+			return;
+		}
 		if ((is_max && cmp < 0) || (!is_max && cmp > 0)) {
 			mem_copy(pBest, pArg);
 		} else {
diff --git a/src/box/sql/mem.c b/src/box/sql/mem.c
index 2595e2fd4..da27cd191 100644
--- a/src/box/sql/mem.c
+++ b/src/box/sql/mem.c
@@ -59,6 +59,44 @@ enum {
 	BUF_SIZE = 32,
 };
 
+/**
+ * Analogue of enum mp_class for enum mp_type. The order of the classes must be
+ * the same as in the enum mp_class.
+ */
+enum mem_class {
+	MEM_CLASS_NULL,
+	MEM_CLASS_BOOL,
+	MEM_CLASS_NUMBER,
+	MEM_CLASS_STR,
+	MEM_CLASS_BIN,
+	MEM_CLASS_UUID,
+	mem_class_max,
+};
+
+static inline enum mem_class
+mem_type_class(enum mem_type type)
+{
+	switch (type) {
+	case MEM_TYPE_NULL:
+		return MEM_CLASS_NULL;
+	case MEM_TYPE_UINT:
+	case MEM_TYPE_INT:
+	case MEM_TYPE_DOUBLE:
+		return MEM_CLASS_NUMBER;
+	case MEM_TYPE_STR:
+		return MEM_CLASS_STR;
+	case MEM_TYPE_BIN:
+		return MEM_CLASS_BIN;
+	case MEM_TYPE_BOOL:
+		return MEM_CLASS_BOOL;
+	case MEM_TYPE_UUID:
+		return MEM_CLASS_UUID;
+	default:
+		break;
+	}
+	return mem_class_max;
+}
+
 bool
 mem_is_field_compatible(const struct Mem *mem, enum field_type type)
 {
@@ -2009,6 +2047,36 @@ mem_cmp_uuid(const struct Mem *a, const struct Mem *b, int *result)
 	return 0;
 }
 
+int
+mem_cmp_scalar(const struct Mem *a, const struct Mem *b, int *result,
+	       const struct coll *coll)
+{
+	enum mem_class class_a = mem_type_class(a->type);
+	enum mem_class class_b = mem_type_class(b->type);
+	if (class_a != class_b) {
+		*result = class_a - class_b;
+		return 0;
+	}
+	switch (class_a) {
+	case MEM_CLASS_NULL:
+		*result = 0;
+		return 0;
+	case MEM_CLASS_BOOL:
+		return mem_cmp_bool(a, b, result);
+	case MEM_CLASS_NUMBER:
+		return mem_cmp_num(a, b, result);
+	case MEM_CLASS_STR:
+		return mem_cmp_str(a, b, result, coll);
+	case MEM_CLASS_BIN:
+		return mem_cmp_bin(a, b, result);
+	case MEM_CLASS_UUID:
+		return mem_cmp_uuid(a, b, result);
+	default:
+		unreachable();
+	}
+	return 0;
+}
+
 /*
  * Both *pMem1 and *pMem2 contain string values. Compare the two values
  * using the collation sequence pColl. As usual, return a negative , zero
@@ -2440,82 +2508,6 @@ sqlVdbeMemTooBig(Mem * p)
 	return 0;
 }
 
-/*
- * Compare the values contained by the two memory cells, returning
- * negative, zero or positive if pMem1 is less than, equal to, or greater
- * than pMem2. Sorting order is NULL's first, followed by numbers (integers
- * and reals) sorted numerically, followed by text ordered by the collating
- * sequence pColl and finally blob's ordered by memcmp().
- *
- * Two NULL values are considered equal by this function.
- */
-int
-sqlMemCompare(const Mem * pMem1, const Mem * pMem2, const struct coll * pColl)
-{
-	int res;
-
-	enum mem_type type1 = pMem1->type;
-	enum mem_type type2 = pMem2->type;
-
-	/* If one value is NULL, it is less than the other. If both values
-	 * are NULL, return 0.
-	 */
-	if (((type1 | type2) & MEM_TYPE_NULL) != 0)
-		return (int)(type2 == MEM_TYPE_NULL) -
-		       (int)(type1 == MEM_TYPE_NULL);
-
-	if (((type1 | type2) & MEM_TYPE_BOOL) != 0) {
-		if ((type1 & type2 & MEM_TYPE_BOOL) != 0) {
-			if (pMem1->u.b == pMem2->u.b)
-				return 0;
-			if (pMem1->u.b)
-				return 1;
-			return -1;
-		}
-		if (type2 == MEM_TYPE_BOOL)
-			return +1;
-		return -1;
-	}
-
-	if (((type1 | type2) & MEM_TYPE_UUID) != 0) {
-		if (mem_cmp_uuid(pMem1, pMem2, &res) == 0)
-			return res;
-		if (type1 != MEM_TYPE_UUID)
-			return +1;
-		return -1;
-	}
-
-	/* At least one of the two values is a number
-	 */
-	if (((type1 | type2) &
-	     (MEM_TYPE_INT | MEM_TYPE_UINT | MEM_TYPE_DOUBLE)) != 0) {
-		if (!mem_is_num(pMem1))
-			return +1;
-		if (!mem_is_num(pMem2))
-			return -1;
-		mem_cmp_num(pMem1, pMem2, &res);
-		return res;
-	}
-
-	/* If one value is a string and the other is a blob, the string is less.
-	 * If both are strings, compare using the collating functions.
-	 */
-	if (((type1 | type2) & MEM_TYPE_STR) != 0) {
-		if (type1 != MEM_TYPE_STR) {
-			return 1;
-		}
-		if (type2 != MEM_TYPE_STR) {
-			return -1;
-		}
-		mem_cmp_str(pMem1, pMem2, &res, pColl);
-		return res;
-	}
-
-	/* Both values must be blobs.  Compare using memcmp().  */
-	mem_cmp_bin(pMem1, pMem2, &res);
-	return res;
-}
-
 int
 sql_vdbemem_finalize(struct Mem *mem, struct func *func)
 {
diff --git a/src/box/sql/mem.h b/src/box/sql/mem.h
index b3cd5c545..bbb99c4d2 100644
--- a/src/box/sql/mem.h
+++ b/src/box/sql/mem.h
@@ -696,6 +696,14 @@ mem_cmp_num(const struct Mem *a, const struct Mem *b, int *result);
 int
 mem_cmp_uuid(const struct Mem *left, const struct Mem *right, int *result);
 
+/**
+ * Compare two MEMs using SCALAR rules and return the result of comparison. MEMs
+ * should be scalars. Original MEMs are not changed.
+ */
+int
+mem_cmp_scalar(const struct Mem *a, const struct Mem *b, int *result,
+	       const struct coll *coll);
+
 /**
  * Convert the given MEM to INTEGER. This function and the function below define
  * the rules that are used to convert values of all other types to INTEGER. In
@@ -961,8 +969,6 @@ int sqlVdbeMemTooBig(Mem *);
 #define VdbeMemDynamic(X) (((X)->flags & MEM_Dyn) != 0 ||\
 			   ((X)->type & (MEM_TYPE_AGG | MEM_TYPE_FRAME)) != 0)
 
-int sqlMemCompare(const Mem *, const Mem *, const struct coll *);
-
 /** MEM manipulate functions. */
 
 /**
diff --git a/src/box/sql/vdbe.c b/src/box/sql/vdbe.c
index 32d02d96e..220e8b269 100644
--- a/src/box/sql/vdbe.c
+++ b/src/box/sql/vdbe.c
@@ -1828,7 +1828,7 @@ case OP_Compare: {
 		assert(i < (int)def->part_count);
 		struct coll *coll = def->parts[i].coll;
 		bool is_rev = def->parts[i].sort_order == SORT_ORDER_DESC;
-		iCompare = sqlMemCompare(&aMem[p1+idx], &aMem[p2+idx], coll);
+		mem_cmp_scalar(&aMem[p1+idx], &aMem[p2+idx], &iCompare, coll);
 		if (iCompare) {
 			if (is_rev)
 				iCompare = -iCompare;
diff --git a/src/box/sql/where.c b/src/box/sql/where.c
index e5f35fbf8..dadc6d4a2 100644
--- a/src/box/sql/where.c
+++ b/src/box/sql/where.c
@@ -1272,12 +1272,14 @@ whereRangeSkipScanEst(Parse * pParse,		/* Parsing & code generating context */
 			rc = sql_stat4_column(db, samples[i].sample_key, nEq,
 					      &pVal);
 			if (rc == 0 && p1 != NULL) {
-				int res = sqlMemCompare(p1, pVal, coll);
+				int res;
+				mem_cmp_scalar(p1, pVal, &res, coll);
 				if (res >= 0)
 					nLower++;
 			}
 			if (rc == 0 && p2 != NULL) {
-				int res = sqlMemCompare(p2, pVal, coll);
+				int res;
+				mem_cmp_scalar(p2, pVal, &res, coll);
 				if (res >= 0)
 					nUpper++;
 			}
diff --git a/test/sql-tap/gh-6164-uuid-follow-ups.test.lua b/test/sql-tap/gh-6164-uuid-follow-ups.test.lua
index 4fc5052d8..6b4a811c3 100755
--- a/test/sql-tap/gh-6164-uuid-follow-ups.test.lua
+++ b/test/sql-tap/gh-6164-uuid-follow-ups.test.lua
@@ -1,6 +1,6 @@
 #!/usr/bin/env tarantool
 local test = require("sqltester")
-test:plan(4)
+test:plan(8)
 
 -- Make sure that function quote() can work with uuid.
 test:do_execsql_test(
@@ -35,4 +35,47 @@ test:do_test(
     end,
     uuid3)
 
+--
+-- Make sure a comparison that includes a UUID and follows the SCALAR rules is
+-- working correctly.
+--
+box.execute([[CREATE TABLE t (i INTEGER PRIMARY KEY, s SCALAR);]])
+box.execute([[INSERT INTO t VALUES (1, ?)]], {uuid1})
+
+test:do_execsql_test(
+    "gh-6164-5",
+    [[
+        SELECT GREATEST(i, s, x'33', 'something') FROM t;
+    ]], {
+        uuid1
+    })
+
+test:do_execsql_test(
+    "gh-6164-6",
+    [[
+        SELECT LEAST(i, s, x'33', 'something') FROM t;
+    ]], {
+        1
+    })
+
+box.execute([[INSERT INTO t VALUES (2, 2);]])
+
+test:do_execsql_test(
+    "gh-6164-7",
+    [[
+        SELECT MAX(s) FROM t;
+    ]], {
+        uuid1
+    })
+
+test:do_execsql_test(
+    "gh-6164-8",
+    [[
+        SELECT MIN(s) FROM t;
+    ]], {
+        2
+    })
+
+box.execute([[DROP TABLE t;]])
+
 test:finish_test()


More information about the Tarantool-patches mailing list