Re: [Tarantool-patches] [PATCH v5 15/52] sql: rework mem_move()

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

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

On Sun, Apr 11, 2021 at 08:10:50PM +0200, Vladislav Shpilevoy wrote:
> I appreciate the work you did here!
> 
> On 09.04.2021 19:37, Mergen Imeev via Tarantool-patches wrote:
> > This patch reworks mem_move(). This function moves all content of source
> > MEM to destination MEM. Source mem is set to NULL.
> > 
> > Part of #5818
> > ---
> >  src/box/sql/mem.c     | 57 +++++++++----------------------------------
> >  src/box/sql/mem.h     |  8 ++++--
> >  src/box/sql/vdbe.c    | 23 +----------------
> >  src/box/sql/vdbeapi.c |  2 +-
> >  4 files changed, 19 insertions(+), 71 deletions(-)
> > 
> > diff --git a/src/box/sql/mem.c b/src/box/sql/mem.c
> > index f75661e04..d56fe56c6 100644
> > --- a/src/box/sql/mem.c
> > +++ b/src/box/sql/mem.c
> > @@ -315,6 +315,17 @@ mem_copy_as_ephemeral(struct Mem *to, const struct Mem *from)
> >  	return;
> >  }
> >  
> > +int
> 
> It can be 'void'. The function never fails.
> 
Fixed.

> > +mem_move(struct Mem *to, struct Mem *from)
> > +{
> > +	mem_destroy(to);
> > +	memcpy(to, from, sizeof(*to));
> > +	from->flags = MEM_Null;
> > +	from->szMalloc = 0;
> > +	from->zMalloc = NULL;
> > +	return 0;
> > +}



Diff:

diff --git a/src/box/sql/mem.c b/src/box/sql/mem.c
index f583dc7c0..2991f902d 100644
--- a/src/box/sql/mem.c
+++ b/src/box/sql/mem.c
@@ -170,7 +170,7 @@ mem_copy_as_ephemeral(struct Mem *to, const struct Mem *from)
 	return;
 }
 
-int
+void
 mem_move(struct Mem *to, struct Mem *from)
 {
 	mem_destroy(to);
@@ -178,7 +178,6 @@ mem_move(struct Mem *to, struct Mem *from)
 	from->flags = MEM_Null;
 	from->szMalloc = 0;
 	from->zMalloc = NULL;
-	return 0;
 }
 
 static inline bool
diff --git a/src/box/sql/mem.h b/src/box/sql/mem.h
index 496fef1e3..beb9826a1 100644
--- a/src/box/sql/mem.h
+++ b/src/box/sql/mem.h
@@ -319,7 +319,7 @@ mem_copy_as_ephemeral(struct Mem *to, const struct Mem *from);
 /**
  * Move all content of source MEM to destination MEM. Source MEM is set to NULL.
  */
-int
+void
 mem_move(struct Mem *to, struct Mem *from);
 
 /**


New patch:


commit e54a891eebb0ae9af9cde630628a5cdb03e00698
Author: Mergen Imeev <imeevma@gmail.com>
Date:   Fri Mar 5 15:30:23 2021 +0300

    sql: rework mem_move()
    
    This patch reworks mem_move(). This function moves all content of source
    MEM to destination MEM. Source mem is set to NULL.
    
    Part of #5818

diff --git a/src/box/sql/mem.c b/src/box/sql/mem.c
index befedf04c..2991f902d 100644
--- a/src/box/sql/mem.c
+++ b/src/box/sql/mem.c
@@ -170,6 +170,16 @@ mem_copy_as_ephemeral(struct Mem *to, const struct Mem *from)
 	return;
 }
 
+void
+mem_move(struct Mem *to, struct Mem *from)
+{
+	mem_destroy(to);
+	memcpy(to, from, sizeof(*to));
+	from->flags = MEM_Null;
+	from->szMalloc = 0;
+	from->zMalloc = NULL;
+}
+
 static inline bool
 mem_has_msgpack_subtype(struct Mem *mem)
 {
@@ -1849,52 +1859,6 @@ vdbe_mem_alloc_blob_region(struct Mem *vdbe_mem, uint32_t size)
 	return 0;
 }
 
-/*
- * Transfer the contents of pFrom to pTo. Any existing value in pTo is
- * freed. If pFrom contains ephemeral data, a copy is made.
- *
- * pFrom contains an SQL NULL when this routine returns.
- */
-void
-sqlVdbeMemMove(Mem * pTo, Mem * pFrom)
-{
-	assert(pFrom->db == 0 || pTo->db == 0 || pFrom->db == pTo->db);
-
-	mem_destroy(pTo);
-	memcpy(pTo, pFrom, sizeof(Mem));
-	pFrom->flags = MEM_Null;
-	pFrom->szMalloc = 0;
-}
-
-/*
- * Change pMem so that its MEM_Str or MEM_Blob value is stored in
- * MEM.zMalloc, where it can be safely written.
- *
- * Return 0 on success or -1 if malloc fails.
- */
-int
-sqlVdbeMemMakeWriteable(Mem * pMem)
-{
-	if ((pMem->flags & (MEM_Str | MEM_Blob)) != 0) {
-		if (ExpandBlob(pMem))
-			return -1;
-		if (pMem->szMalloc == 0 || pMem->z != pMem->zMalloc) {
-			if (sqlVdbeMemGrow(pMem, pMem->n + 2, 1)) {
-				return -1;
-			}
-			pMem->z[pMem->n] = 0;
-			pMem->z[pMem->n + 1] = 0;
-			pMem->flags |= MEM_Term;
-		}
-	}
-	pMem->flags &= ~MEM_Ephem;
-#ifdef SQL_DEBUG
-	pMem->pScopyFrom = 0;
-#endif
-
-	return 0;
-}
-
 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 e30e5466e..beb9826a1 100644
--- a/src/box/sql/mem.h
+++ b/src/box/sql/mem.h
@@ -316,6 +316,12 @@ mem_copy(struct Mem *to, const struct Mem *from);
 void
 mem_copy_as_ephemeral(struct Mem *to, const struct Mem *from);
 
+/**
+ * Move all content of source MEM to destination MEM. Source MEM is set to NULL.
+ */
+void
+mem_move(struct Mem *to, struct Mem *from);
+
 /**
  * Simple type to str convertor. It is used to simplify
  * error reporting.
@@ -563,8 +569,6 @@ mem_is_type_compatible(struct Mem *mem, enum field_type type);
 
 int
 vdbe_mem_alloc_blob_region(struct Mem *vdbe_mem, uint32_t size);
-void sqlVdbeMemMove(Mem *, Mem *);
-int sqlVdbeMemMakeWriteable(Mem *);
 
 /**
  * Memory cell mem contains the context of an aggregate function.
diff --git a/src/box/sql/vdbe.c b/src/box/sql/vdbe.c
index 50d9dd78c..b3b20a374 100644
--- a/src/box/sql/vdbe.c
+++ b/src/box/sql/vdbe.c
@@ -197,21 +197,6 @@ vdbeTakeBranch(int iSrcLine, u8 I, u8 M)
 }
 #endif
 
-/*
- * An ephemeral string value (signified by the MEM_Ephem flag) contains
- * a pointer to a dynamically allocated string where some other entity
- * is responsible for deallocating that string.  Because the register
- * does not control the string, it might be deleted without the register
- * knowing it.
- *
- * This routine converts an ephemeral string into a dynamically allocated
- * string that the register itself controls.  In other words, it
- * converts an MEM_Ephem string into a string with P.z==P.zMalloc.
- */
-#define Deephemeralize(P)					\
-	if (((P)->flags&MEM_Ephem)!=0				\
-	    && sqlVdbeMemMakeWriteable(P)) { goto no_mem;}
-
 /* Return true if the cursor was opened using the OP_OpenSorter opcode. */
 #define isSorter(x) ((x)->eCurType==CURTYPE_SORTER)
 
@@ -981,13 +966,7 @@ case OP_Move: {
 		assert(pIn1<=&aMem[(p->nMem+1 - p->nCursor)]);
 		assert(memIsValid(pIn1));
 		memAboutToChange(p, pOut);
-		sqlVdbeMemMove(pOut, pIn1);
-#ifdef SQL_DEBUG
-		if (pOut->pScopyFrom>=&aMem[p1] && pOut->pScopyFrom<pOut) {
-			pOut->pScopyFrom += pOp->p2 - p1;
-		}
-#endif
-		Deephemeralize(pOut);
+		mem_move(pOut, pIn1);
 		REGISTER_TRACE(p, p2++, pOut);
 		pIn1++;
 		pOut++;
diff --git a/src/box/sql/vdbeapi.c b/src/box/sql/vdbeapi.c
index 7951996ea..8e69e3c38 100644
--- a/src/box/sql/vdbeapi.c
+++ b/src/box/sql/vdbeapi.c
@@ -980,7 +980,7 @@ sqlTransferBindings(sql_stmt * pFromStmt, sql_stmt * pToStmt)
 	assert(pTo->db == pFrom->db);
 	assert(pTo->nVar == pFrom->nVar);
 	for (i = 0; i < pFrom->nVar; i++) {
-		sqlVdbeMemMove(&pTo->aVar[i], &pFrom->aVar[i]);
+		mem_move(&pTo->aVar[i], &pFrom->aVar[i]);
 	}
 	return 0;
 }