Re: [Tarantool-patches] [PATCH v4 01/16] sql: remove MEM_Zero flag from struct MEM

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

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

On Mon, Oct 04, 2021 at 11:51:42PM +0200, Vladislav Shpilevoy wrote:
> Hi! Thanks for the patch!
> 
> See 2 comments below.
> 
> > diff --git a/src/box/sql/func.c b/src/box/sql/func.c
> > index 29d713fd0..ff0c461ce 100644
> > --- a/src/box/sql/func.c
> > +++ b/src/box/sql/func.c
> > @@ -1272,11 +1272,19 @@ zeroblobFunc(sql_context * context, int argc, sql_value ** argv)
> >  	n = mem_get_int_unsafe(argv[0]);
> >  	if (n < 0)
> >  		n = 0;
> > -	if (sql_result_zeroblob64(context, n) != 0) {
> > +	if (n > sql_get()->aLimit[SQL_LIMIT_LENGTH]) {
> >  		diag_set(ClientError, ER_SQL_EXECUTE, "string or binary string"\
> >  			 "is too big");
> >  		context->is_aborted = true;
> > +		return;
> > +	}
> > +	char *str = sqlDbMallocRawNN(sql_get(), n);
> > +	memset(str, 0, n);
> 
> 1. There is sqlDbMallocZero().
> 
Thanks, fixed.

> > +	if (str == NULL) {
> > +		context->is_aborted = true;
> > +		return;
> >  	}
> > +	mem_set_bin_allocated(context->pOut, str, n);
> >  }
> >  
> >  /*
> > diff --git a/src/box/sql/mem.c b/src/box/sql/mem.c
> > index 5e23c901c..24d6d7dbf 100644
> > --- a/src/box/sql/mem.c
> > +++ b/src/box/sql/mem.c
> > @@ -1869,8 +1850,6 @@ mem_get_bin(const struct Mem *mem, const char **s)
> >  		*s = mem->n > 0 ? mem->z : NULL;
> >  		return 0;
> >  	}
> > -	if (mem->type != MEM_TYPE_BIN || (mem->flags & MEM_Zero) != 0)
> > -		return -1;
> 
> 2. If the type is not MEM_TYPE_BIN, you will return garbage. Maybe
> keep return -1 for other types?
> 
True, fixed. There is a case where the behavior will be different - I
mean the case where new_size < szMalloc and new_size + n > szMalloc,
but that doesn't seem to be a very common case.

> >  	*s = mem->z;
> >  	return 0;
> >  }


Diff:

diff --git a/src/box/sql/func.c b/src/box/sql/func.c
index ff0c461ce..187456d2c 100644
--- a/src/box/sql/func.c
+++ b/src/box/sql/func.c
@@ -1278,8 +1278,7 @@ zeroblobFunc(sql_context * context, int argc, sql_value ** argv)
 		context->is_aborted = true;
 		return;
 	}
-	char *str = sqlDbMallocRawNN(sql_get(), n);
-	memset(str, 0, n);
+	char *str = sqlDbMallocZero(sql_get(), n);
 	if (str == NULL) {
 		context->is_aborted = true;
 		return;
diff --git a/src/box/sql/mem.c b/src/box/sql/mem.c
index 24d6d7dbf..117a44314 100644
--- a/src/box/sql/mem.c
+++ b/src/box/sql/mem.c
@@ -1850,6 +1850,8 @@ mem_get_bin(const struct Mem *mem, const char **s)
 		*s = mem->n > 0 ? mem->z : NULL;
 		return 0;
 	}
+	if (mem->type != MEM_TYPE_BIN)
+		return -1;
 	*s = mem->z;
 	return 0;
 }


New patch:

commit 37ccef0873f7d62271d0c46352f8f9cbfb73c22f
Author: Mergen Imeev <imeevma@gmail.com>
Date:   Fri Oct 1 14:05:23 2021 +0300

    sql: remove MEM_Zero flag from struct MEM
    
    This patch removes zeroblob optimization from SQL code. This
    optimization complicates the code, and there is almost no profit from
    it.

diff --git a/src/box/sql/func.c b/src/box/sql/func.c
index 29d713fd0..187456d2c 100644
--- a/src/box/sql/func.c
+++ b/src/box/sql/func.c
@@ -1272,11 +1272,18 @@ zeroblobFunc(sql_context * context, int argc, sql_value ** argv)
 	n = mem_get_int_unsafe(argv[0]);
 	if (n < 0)
 		n = 0;
-	if (sql_result_zeroblob64(context, n) != 0) {
+	if (n > sql_get()->aLimit[SQL_LIMIT_LENGTH]) {
 		diag_set(ClientError, ER_SQL_EXECUTE, "string or binary string"\
 			 "is too big");
 		context->is_aborted = true;
+		return;
+	}
+	char *str = sqlDbMallocZero(sql_get(), n);
+	if (str == NULL) {
+		context->is_aborted = true;
+		return;
 	}
+	mem_set_bin_allocated(context->pOut, str, n);
 }
 
 /*
diff --git a/src/box/sql/mem.c b/src/box/sql/mem.c
index 5e23c901c..117a44314 100644
--- a/src/box/sql/mem.c
+++ b/src/box/sql/mem.c
@@ -503,19 +503,6 @@ mem_copy_bin(struct Mem *mem, const char *value, uint32_t size)
 	return 0;
 }
 
-void
-mem_set_zerobin(struct Mem *mem, int n)
-{
-	mem_destroy(mem);
-	if (n < 0)
-		n = 0;
-	mem->u.nZero = n;
-	mem->z = NULL;
-	mem->n = 0;
-	mem->type = MEM_TYPE_BIN;
-	mem->flags = MEM_Zero;
-}
-
 static inline void
 set_msgpack_value(struct Mem *mem, char *value, uint32_t size, int alloc_type,
 		  enum mem_type type)
@@ -806,8 +793,6 @@ static inline int
 bin_to_str(struct Mem *mem)
 {
 	assert(mem->type == MEM_TYPE_BIN);
-	if (ExpandBlob(mem) != 0)
-		return -1;
 	mem->type = MEM_TYPE_STR;
 	mem->flags &= ~MEM_Scalar;
 	return 0;
@@ -817,8 +802,6 @@ static inline int
 bin_to_str0(struct Mem *mem)
 {
 	assert(mem->type == MEM_TYPE_BIN);
-	if (ExpandBlob(mem) != 0)
-		return -1;
 	if (sqlVdbeMemGrow(mem, mem->n + 1, 1) != 0)
 		return -1;
 	mem->z[mem->n] = '\0';
@@ -831,8 +814,6 @@ static inline int
 bin_to_uuid(struct Mem *mem)
 {
 	assert(mem->type == MEM_TYPE_BIN);
-	if (ExpandBlob(mem) != 0)
-		return -1;
 	if (mem->n != UUID_LEN ||
 	    tt_uuid_validate((struct tt_uuid *)mem->z) != 0)
 		return -1;
@@ -1869,7 +1850,7 @@ mem_get_bin(const struct Mem *mem, const char **s)
 		*s = mem->n > 0 ? mem->z : NULL;
 		return 0;
 	}
-	if (mem->type != MEM_TYPE_BIN || (mem->flags & MEM_Zero) != 0)
+	if (mem->type != MEM_TYPE_BIN)
 		return -1;
 	*s = mem->z;
 	return 0;
@@ -1880,11 +1861,7 @@ mem_len(const struct Mem *mem, uint32_t *len)
 {
 	if (!mem_is_bytes(mem))
 		return -1;
-	assert((mem->flags & MEM_Zero) == 0 || mem->type == MEM_TYPE_BIN);
-	if ((mem->flags & MEM_Zero) != 0)
-		*len = mem->n + mem->u.nZero;
-	else
-		*len = mem->n;
+	*len = mem->n;
 	return 0;
 }
 
@@ -1910,9 +1887,6 @@ mem_copy(struct Mem *to, const struct Mem *from)
 		return 0;
 	if ((to->flags & MEM_Static) != 0)
 		return 0;
-	assert((to->flags & MEM_Zero) == 0 || to->type == MEM_TYPE_BIN);
-	if ((to->flags & MEM_Zero) != 0)
-		return sqlVdbeMemExpandBlob(to);
 	to->zMalloc = sqlDbRealloc(to->db, to->zMalloc, MAX(32, to->n));
 	assert(to->zMalloc != NULL || sql_get()->mallocFailed != 0);
 	if (to->zMalloc == NULL)
@@ -1937,7 +1911,7 @@ mem_copy_as_ephemeral(struct Mem *to, const struct Mem *from)
 		return;
 	if ((to->flags & (MEM_Static | MEM_Ephem)) != 0)
 		return;
-	to->flags &= MEM_Term | MEM_Zero;
+	to->flags &= MEM_Term;
 	to->flags |= MEM_Ephem;
 	return;
 }
@@ -1954,7 +1928,7 @@ mem_move(struct Mem *to, struct Mem *from)
 }
 
 int
-mem_concat(struct Mem *a, struct Mem *b, struct Mem *result)
+mem_concat(const struct Mem *a, const struct Mem *b, struct Mem *result)
 {
 	if (mem_is_any_null(a, b)) {
 		mem_set_null(result);
@@ -1981,9 +1955,6 @@ mem_concat(struct Mem *a, struct Mem *b, struct Mem *result)
 		return -1;
 	}
 
-	if (ExpandBlob(a) != 0 || ExpandBlob(b) != 0)
-		return -1;
-
 	uint32_t size = a->n + b->n;
 	if ((int)size > sql_get()->aLimit[SQL_LIMIT_LENGTH]) {
 		diag_set(ClientError, ER_SQL_EXECUTE, "string or blob too big");
@@ -2330,37 +2301,8 @@ static int
 mem_cmp_bin(const struct Mem *a, const struct Mem *b)
 {
 	assert((a->type & b->type & MEM_TYPE_BIN) != 0);
-	int an = a->n;
-	int bn = b->n;
-	int minlen = MIN(an, bn);
-
-	/*
-	 * It is possible to have a Blob value that has some non-zero content
-	 * followed by zero content.  But that only comes up for Blobs formed
-	 * by the OP_MakeRecord opcode, and such Blobs never get passed into
-	 * mem_compare().
-	 */
-	assert((a->flags & MEM_Zero) == 0 || an == 0);
-	assert((b->flags & MEM_Zero) == 0 || bn == 0);
-
-	if ((a->flags & b->flags & MEM_Zero) != 0)
-		return a->u.nZero - b->u.nZero;
-	if ((a->flags & MEM_Zero) != 0) {
-		for (int i = 0; i < minlen; ++i) {
-			if (b->z[i] != 0)
-				return -1;
-		}
-		return a->u.nZero - bn;
-	}
-	if ((b->flags & MEM_Zero) != 0) {
-		for (int i = 0; i < minlen; ++i) {
-			if (a->z[i] != 0)
-				return 1;
-		}
-		return b->u.nZero - an;
-	}
-	int res = memcmp(a->z, b->z, minlen);
-	return res != 0 ? res : an - bn;
+	int res = memcmp(a->z, b->z, MIN(a->n, b->n));
+	return res != 0 ? res : a->n - b->n;
 }
 
 static int
@@ -2797,10 +2739,6 @@ sqlVdbeMemPrettyPrint(Mem *pMem, char *zBuf)
 		}
 		sql_snprintf(100, zCsr, "]%s", "(8)");
 		zCsr += sqlStrlen30(zCsr);
-		if (f & MEM_Zero) {
-			sql_snprintf(100, zCsr,"+%dz",pMem->u.nZero);
-			zCsr += sqlStrlen30(zCsr);
-		}
 		*zCsr = '\0';
 	} else if (pMem->type == MEM_TYPE_STR) {
 		int j, k;
@@ -2886,32 +2824,6 @@ registerTrace(int iReg, Mem *p) {
 }
 #endif
 
-/*
- * If the given Mem* has a zero-filled tail, turn it into an ordinary
- * blob stored in dynamically allocated space.
- */
-int
-sqlVdbeMemExpandBlob(Mem * pMem)
-{
-	int nByte;
-	assert(pMem->flags & MEM_Zero);
-	assert(pMem->type == MEM_TYPE_BIN);
-
-	/* Set nByte to the number of bytes required to store the expanded blob. */
-	nByte = pMem->n + pMem->u.nZero;
-	if (nByte <= 0) {
-		nByte = 1;
-	}
-	if (sqlVdbeMemGrow(pMem, nByte, 1)) {
-		return -1;
-	}
-
-	memset(&pMem->z[pMem->n], 0, pMem->u.nZero);
-	pMem->n += pMem->u.nZero;
-	pMem->flags &= ~(MEM_Zero | MEM_Term);
-	return 0;
-}
-
 static int
 sqlVdbeMemGrow(struct Mem *pMem, int n, int bPreserve)
 {
@@ -3036,13 +2948,8 @@ int
 sqlVdbeMemTooBig(Mem * p)
 {
 	assert(p->db != 0);
-	if (mem_is_bytes(p)) {
-		int n = p->n;
-		if (p->flags & MEM_Zero) {
-			n += p->u.nZero;
-		}
-		return n > p->db->aLimit[SQL_LIMIT_LENGTH];
-	}
+	if (mem_is_bytes(p))
+		return p->n > p->db->aLimit[SQL_LIMIT_LENGTH];
 	return 0;
 }
 
@@ -3251,14 +3158,8 @@ mpstream_encode_vdbe_mem(struct mpstream *stream, struct Mem *var)
 		mpstream_encode_double(stream, var->u.r);
 		return;
 	case MEM_TYPE_BIN:
-		if ((var->flags & MEM_Zero) != 0) {
-			mpstream_encode_binl(stream, var->n + var->u.nZero);
-			mpstream_memcpy(stream, var->z, var->n);
-			mpstream_memset(stream, 0, var->u.nZero);
-		} else {
-			mpstream_encode_binl(stream, var->n);
-			mpstream_memcpy(stream, var->z, var->n);
-		}
+		mpstream_encode_binl(stream, var->n);
+		mpstream_memcpy(stream, var->z, var->n);
 		return;
 	case MEM_TYPE_ARRAY:
 	case MEM_TYPE_MAP:
diff --git a/src/box/sql/mem.h b/src/box/sql/mem.h
index 0da45b8af..1574da22d 100644
--- a/src/box/sql/mem.h
+++ b/src/box/sql/mem.h
@@ -68,7 +68,6 @@ struct Mem {
 		i64 i;		/* Integer value used when MEM_Int is set in flags */
 		uint64_t u;	/* Unsigned integer used when MEM_UInt is set. */
 		bool b;         /* Boolean value used when MEM_Bool is set in flags */
-		int nZero;	/* Used when bit MEM_Zero is set in flags */
 		void *p;	/* Generic pointer */
 		/**
 		 * A pointer to function implementation.
@@ -111,7 +110,6 @@ struct Mem {
 #define MEM_Dyn       0x0800	/* Need to call Mem.xDel() on Mem.z */
 #define MEM_Static    0x1000	/* Mem.z points to a static string */
 #define MEM_Ephem     0x2000	/* Mem.z points to an ephemeral string */
-#define MEM_Zero      0x8000	/* Mem.i contains count of 0s appended to blob */
 
 static inline bool
 mem_is_null(const struct Mem *mem)
@@ -246,13 +244,6 @@ mem_is_cleared(const struct Mem *mem)
 	return (mem->flags & MEM_Cleared) != 0;
 }
 
-static inline bool
-mem_is_zerobin(const struct Mem *mem)
-{
-	assert((mem->flags & MEM_Zero) == 0 || mem->type == MEM_TYPE_BIN);
-	return (mem->flags & MEM_Zero) != 0;
-}
-
 static inline bool
 mem_is_same_type(const struct Mem *mem1, const struct Mem *mem2)
 {
@@ -474,12 +465,6 @@ mem_set_binl(struct Mem *mem, char *value, uint32_t size,
 		return mem_set_bin_dynamic(mem, value, size);
 }
 
-/**
- * Clear MEM and set it to VARBINARY. The binary value consist of n zero bytes.
- */
-void
-mem_set_zerobin(struct Mem *mem, int n);
-
 /**
  * Copy binary value to a newly allocated memory. The MEM type becomes
  * VARBINARY.
@@ -603,7 +588,7 @@ mem_move(struct Mem *to, struct Mem *from);
  * result MEM is set to NULL even if the result MEM is actually the first MEM.
  */
 int
-mem_concat(struct Mem *left, struct Mem *right, struct Mem *result);
+mem_concat(const struct Mem *a, const struct Mem *b, struct Mem *result);
 
 /**
  * Add the first MEM to the second MEM and write the result to the third MEM.
@@ -935,11 +920,6 @@ registerTrace(int iReg, Mem *p);
 #define memIsValid(M)  ((M)->type != MEM_TYPE_INVALID)
 #endif
 
-int sqlVdbeMemExpandBlob(struct Mem *);
-#define ExpandBlob(P) (((P)->flags&MEM_Zero)?sqlVdbeMemExpandBlob(P):0)
-
-/** Setters = Change MEM value. */
-
 int sqlVdbeMemClearAndResize(struct Mem * pMem, int n);
 
 void sqlValueFree(struct Mem *);
diff --git a/src/box/sql/sqlInt.h b/src/box/sql/sqlInt.h
index 2e250dc29..eac6bcec8 100644
--- a/src/box/sql/sqlInt.h
+++ b/src/box/sql/sqlInt.h
@@ -394,13 +394,6 @@ void
 sql_result_value(sql_context *,
 		     sql_value *);
 
-void
-sql_result_zeroblob(sql_context *, int n);
-
-int
-sql_result_zeroblob64(sql_context *,
-			  sql_uint64 n);
-
 char *
 sql_mprintf(const char *, ...);
 char *
@@ -631,13 +624,6 @@ int
 sql_bind_text64(sql_stmt *, int, const char *,
 		    sql_uint64, void (*)(void *));
 
-int
-sql_bind_zeroblob(sql_stmt *, int, int n);
-
-int
-sql_bind_zeroblob64(sql_stmt *, int,
-			sql_uint64);
-
 int
 sql_bind_uuid(struct sql_stmt *stmt, int i, const struct tt_uuid *uuid);
 
diff --git a/src/box/sql/vdbe.c b/src/box/sql/vdbe.c
index 44533fb3e..86550541b 100644
--- a/src/box/sql/vdbe.c
+++ b/src/box/sql/vdbe.c
@@ -1462,8 +1462,6 @@ case OP_MustBeInt: {            /* jump, in1 */
  */
 case OP_Cast: {                  /* in1 */
 	pIn1 = &aMem[pOp->p1];
-	if (ExpandBlob(pIn1) != 0)
-		goto abort_due_to_error;
 	rc = mem_cast_explicit(pIn1, pOp->p2);
 	UPDATE_MAX_BLOBSIZE(pIn1);
 	if (rc == 0)
@@ -2772,8 +2770,6 @@ case OP_Found: {        /* jump, in3 */
 #ifdef SQL_DEBUG
 		for(ii=0; ii<r.nField; ii++) {
 			assert(memIsValid(&r.aMem[ii]));
-			assert(!mem_is_zerobin(&r.aMem[ii]) ||
-			       r.aMem[ii].n == 0);
 			if (ii != 0)
 				REGISTER_TRACE(p, pOp->p3+ii, &r.aMem[ii]);
 		}
@@ -2784,7 +2780,6 @@ case OP_Found: {        /* jump, in3 */
 		pFree = pIdxKey = sqlVdbeAllocUnpackedRecord(db, pC->key_def);
 		if (pIdxKey==0) goto no_mem;
 		assert(mem_is_bin(pIn3));
-		(void)ExpandBlob(pIn3);
 		sqlVdbeRecordUnpackMsgpack(pC->key_def,
 					       pIn3->z, pIdxKey);
 	}
@@ -3411,8 +3406,7 @@ case OP_SorterInsert: {      /* in2 */
 	assert(isSorter(cursor));
 	pIn2 = &aMem[pOp->p2];
 	assert(mem_is_bin(pIn2));
-	if (ExpandBlob(pIn2) != 0 ||
-	    sqlVdbeSorterWrite(cursor, pIn2) != 0)
+	if (sqlVdbeSorterWrite(cursor, pIn2) != 0)
 		goto abort_due_to_error;
 	break;
 }
@@ -3445,8 +3439,6 @@ case OP_IdxReplace:
 case OP_IdxInsert: {
 	pIn2 = &aMem[pOp->p1];
 	assert(mem_is_bin(pIn2));
-	if (ExpandBlob(pIn2) != 0)
-		goto abort_due_to_error;
 	struct space *space;
 	if (pOp->p4type == P4_SPACEPTR)
 		space = pOp->p4.space;
diff --git a/src/box/sql/vdbeapi.c b/src/box/sql/vdbeapi.c
index 115940227..97bd19863 100644
--- a/src/box/sql/vdbeapi.c
+++ b/src/box/sql/vdbeapi.c
@@ -236,25 +236,6 @@ sql_result_value(sql_context * pCtx, sql_value * pValue)
 		pCtx->is_aborted = true;
 }
 
-void
-sql_result_zeroblob(sql_context * pCtx, int n)
-{
-	mem_set_zerobin(pCtx->pOut, n);
-}
-
-int
-sql_result_zeroblob64(sql_context * pCtx, u64 n)
-{
-	Mem *pOut = pCtx->pOut;
-	if (n > (u64) pOut->db->aLimit[SQL_LIMIT_LENGTH]) {
-		diag_set(ClientError, ER_SQL_EXECUTE, "string or binary string"\
-			 "is too big");
-		return -1;
-	}
-	mem_set_zerobin(pCtx->pOut, (int)n);
-	return 0;
-}
-
 /*
  * Execute the statement pStmt, either until a row of data is ready, the
  * statement is completely executed or an error occurs.
@@ -818,29 +799,6 @@ sql_bind_text64(sql_stmt * pStmt,
 	}
 }
 
-int
-sql_bind_zeroblob(sql_stmt * pStmt, int i, int n)
-{
-	Vdbe *p = (Vdbe *) pStmt;
-	if (vdbeUnbind(p, i) != 0)
-		return -1;
-	mem_set_zerobin(&p->aVar[i - 1], n);
-	return 0;
-}
-
-int
-sql_bind_zeroblob64(sql_stmt * pStmt, int i, sql_uint64 n)
-{
-	Vdbe *p = (Vdbe *) pStmt;
-	if (n > (u64) p->db->aLimit[SQL_LIMIT_LENGTH]) {
-		diag_set(ClientError, ER_SQL_EXECUTE, "string or binary string"\
-			 "is too big");
-		return -1;
-	}
-	assert((n & 0x7FFFFFFF) == n);
-	return sql_bind_zeroblob(pStmt, i, n);
-}
-
 int
 sql_bind_uuid(struct sql_stmt *stmt, int i, const struct tt_uuid *uuid)
 {