Re: [PATCH] Redudant initilization - Mailing list pgsql-hackers

Hello.

At Sat, 28 Mar 2020 19:04:00 -0300, Ranier Vilela <ranier.vf@gmail.com> wrote in
> Hi,
> This patch fixes some redundant initilization, that are safe to remove.

> diff --git a/src/backend/access/gist/gistxlog.c b/src/backend/access/gist/gistxlog.c
> index d3f3a7b803..ffaa2b1ab4 100644
> --- a/src/backend/access/gist/gistxlog.c
> +++ b/src/backend/access/gist/gistxlog.c
> @@ -396,7 +396,7 @@ gistRedoPageReuse(XLogReaderState *record)
>       if (InHotStandby)
>       {
>               FullTransactionId latestRemovedFullXid = xlrec->latestRemovedFullXid;
> -             FullTransactionId nextFullXid = ReadNextFullTransactionId();
> +             FullTransactionId nextFullXid;

I'd prefer to preserve this and remove the latter.

> diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
> index 9d9e915979..795cf349eb 100644
> --- a/src/backend/catalog/heap.c
> +++ b/src/backend/catalog/heap.c
> @@ -3396,7 +3396,7 @@ List *
>  heap_truncate_find_FKs(List *relationIds)
>  {
>       List       *result = NIL;
> -     List       *oids = list_copy(relationIds);
> +     List       *oids;

This was just a waste of memory, the fix looks fine.

> diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
> index c5b771c531..37fbeef841 100644
> --- a/src/backend/storage/smgr/md.c
> +++ b/src/backend/storage/smgr/md.c
> @@ -730,9 +730,11 @@ mdwrite(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
>  BlockNumber
>  mdnblocks(SMgrRelation reln, ForkNumber forknum)
>  {
> -     MdfdVec    *v = mdopenfork(reln, forknum, EXTENSION_FAIL);
> +     MdfdVec    *v;
>       BlockNumber nblocks;
> -     BlockNumber segno = 0;
> +     BlockNumber segno;
> +
> +    mdopenfork(reln, forknum, EXTENSION_FAIL);
> 
>       /* mdopen has opened the first segment */
>       Assert(reln->md_num_open_segs[forknum] > 0);

It doesn't seems *to me* an issue.

> diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
> index 8bb00abb6b..7a6a2ecbe9 100644
> --- a/src/backend/utils/adt/json.c
> +++ b/src/backend/utils/adt/json.c
> @@ -990,7 +990,7 @@ catenate_stringinfo_string(StringInfo buffer, const char *addon)
>  Datum
>  json_build_object(PG_FUNCTION_ARGS)
>  {
> -     int                     nargs = PG_NARGS();
> +     int                     nargs;

This part looks fine.

>       int                     i;
>       const char *sep = "";
>       StringInfo      result;
> @@ -998,6 +998,8 @@ json_build_object(PG_FUNCTION_ARGS)
>       bool       *nulls;
>       Oid                *types;
> 
> +    PG_NARGS();
> +
>       /* fetch argument values to build the object */
>       nargs = extract_variadic_args(fcinfo, 0, false, &args, &types, &nulls);

PG_NARGS() doesn't have a side-effect so no need to call independently.

> diff --git a/src/backend/utils/mmgr/mcxt.c b/src/backend/utils/mmgr/mcxt.c
> index 9e24fec72d..fb0e833b2d 100644
> --- a/src/backend/utils/mmgr/mcxt.c
> +++ b/src/backend/utils/mmgr/mcxt.c
> @@ -475,7 +475,7 @@ MemoryContextMemAllocated(MemoryContext context, bool recurse)
> 
>       if (recurse)
>       {
> -             MemoryContext child = context->firstchild;
> +             MemoryContext child;
> 
>               for (child = context->firstchild;
>                        child != NULL;

This looks fine.