Re: error context for vacuum to include block number

It occured to me that there's an issue with sharing vacrelstats between
scan/vacuum, since blkno and stage are set by the heap/index vacuum routines,
but not reset on their return to heap scan. Not sure if we should reset them,
or go back to using a separate struct, like it was here:
https://www.postgresql.org/message-id/20200120054159.GT26045%40telsasoft.com

On Sun, Jan 26, 2020 at 11:38:13PM -0600, Justin Pryzby wrote:
> From 592a77554f99b5ff9035c55bf19a79a1443ae59e Mon Sep 17 00:00:00 2001
> From: Justin Pryzby <pryzbyj(at)telsasoft(dot)com>
> Date: Thu, 12 Dec 2019 20:54:37 -0600
> Subject: [PATCH v14 2/3] vacuum errcontext to show block being processed
>
> As requested here.
> https://www.postgresql.org/message-id/20190807235154.erbmr4o4bo6vgnjv%40alap3.anarazel.de
> ---
> src/backend/access/heap/vacuumlazy.c | 85 +++++++++++++++++++++++++++++++++++-
> 1 file changed, 84 insertions(+), 1 deletion(-)
>
> diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c
> index 114428b..a62dc79 100644
> --- a/src/backend/access/heap/vacuumlazy.c
> +++ b/src/backend/access/heap/vacuumlazy.c
> @@ -290,8 +290,14 @@ typedef struct LVRelStats
> int num_index_scans;
> TransactionId latestRemovedXid;
> bool lock_waiter_detected;
> -} LVRelStats;
>
> + /* Used by the error callback */
> + char *relname;
> + char *relnamespace;
> + BlockNumber blkno;
> + char *indname;
> + int stage; /* 0: scan heap; 1: vacuum heap; 2: vacuum index */
> +} LVRelStats;
>
> /* A few variables that don't seem worth passing around as parameters */
> static int elevel = -1;
> @@ -360,6 +366,7 @@ static void end_parallel_vacuum(Relation *Irel, IndexBulkDeleteResult **stats,
> LVParallelState *lps, int nindexes);
> static LVSharedIndStats *get_indstats(LVShared *lvshared, int n);
> static bool skip_parallel_vacuum_index(Relation indrel, LVShared *lvshared);
> +static void vacuum_error_callback(void *arg);
>
>
> /*
> @@ -721,6 +728,7 @@ lazy_scan_heap(Relation onerel, VacuumParams *params,
> PROGRESS_VACUUM_MAX_DEAD_TUPLES
> };
> int64 initprog_val[3];
> + ErrorContextCallback errcallback;
>
> pg_rusage_init(&ru0);
>
> @@ -867,6 +875,17 @@ lazy_scan_heap(Relation onerel, VacuumParams *params,
> else
> skipping_blocks = false;
>
> + /* Setup error traceback support for ereport() */
> + vacrelstats.relnamespace = get_namespace_name(RelationGetNamespace(onerel));
> + vacrelstats.relname = relname;
> + vacrelstats.blkno = InvalidBlockNumber; /* Not known yet */
> + vacrelstats.stage = 0;
> +
> + errcallback.callback = vacuum_error_callback;
> + errcallback.arg = (void *) &vacrelstats;
> + errcallback.previous = error_context_stack;
> + error_context_stack = &errcallback;
> +
> for (blkno = 0; blkno < nblocks; blkno++)
> {
> Buffer buf;
> @@ -888,6 +907,8 @@ lazy_scan_heap(Relation onerel, VacuumParams *params,
> #define FORCE_CHECK_PAGE() \
> (blkno == nblocks - 1 && should_attempt_truncation(params))
>
> + vacrelstats.blkno = blkno;
> +
> pgstat_progress_update_param(PROGRESS_VACUUM_HEAP_BLKS_SCANNED, blkno);
>
> if (blkno == next_unskippable_block)
> @@ -984,12 +1005,18 @@ lazy_scan_heap(Relation onerel, VacuumParams *params,
> vmbuffer = InvalidBuffer;
> }
>
> + /* Pop the error context stack */
> + error_context_stack = errcallback.previous;
> +
> /* Work on all the indexes, then the heap */
> lazy_vacuum_all_indexes(onerel, Irel, indstats,
> lps, nindexes);
> /* Remove tuples from heap */
> lazy_vacuum_heap(onerel);
>
> + /* Replace error context while continuing heap scan */
> + error_context_stack = &errcallback;
> +
> /*
> * Forget the now-vacuumed tuples, and press on, but be careful
> * not to reset latestRemovedXid since we want that value to be
> @@ -1593,6 +1620,9 @@ lazy_scan_heap(Relation onerel, VacuumParams *params,
> RecordPageWithFreeSpace(onerel, blkno, freespace);
> }
>
> + /* Pop the error context stack */
> + error_context_stack = errcallback.previous;
> +
> /* report that everything is scanned and vacuumed */
> pgstat_progress_update_param(PROGRESS_VACUUM_HEAP_BLKS_SCANNED, blkno);
>
> @@ -1768,11 +1798,24 @@ lazy_vacuum_heap(Relation onerel)
> int npages;
> PGRUsage ru0;
> Buffer vmbuffer = InvalidBuffer;
> + ErrorContextCallback errcallback;
>
> /* Report that we are now vacuuming the heap */
> pgstat_progress_update_param(PROGRESS_VACUUM_PHASE,
> PROGRESS_VACUUM_PHASE_VACUUM_HEAP);
>
> + /*
> + * Setup error traceback support for ereport()
> + * ->relnamespace and ->relname are already set
> + */
> + vacrelstats.blkno = InvalidBlockNumber; /* Not known yet */
> + vacrelstats.stage = 1;
> +
> + errcallback.callback = vacuum_error_callback;
> + errcallback.arg = (void *) &vacrelstats;
> + errcallback.previous = error_context_stack;
> + error_context_stack = &errcallback;
> +
> pg_rusage_init(&ru0);
> npages = 0;
>
> @@ -1787,6 +1830,7 @@ lazy_vacuum_heap(Relation onerel)
> vacuum_delay_point();
>
> tblk = ItemPointerGetBlockNumber(&vacrelstats.dead_tuples->itemptrs[tupindex]);
> + vacrelstats.blkno = tblk;
> buf = ReadBufferExtended(onerel, MAIN_FORKNUM, tblk, RBM_NORMAL,
> vac_strategy);
> if (!ConditionalLockBufferForCleanup(buf))
> @@ -1807,6 +1851,9 @@ lazy_vacuum_heap(Relation onerel)
> npages++;
> }
>
> + /* Pop the error context stack */
> + error_context_stack = errcallback.previous;
> +
> if (BufferIsValid(vmbuffer))
> {
> ReleaseBuffer(vmbuffer);
> @@ -2314,6 +2361,8 @@ lazy_vacuum_index(Relation indrel, IndexBulkDeleteResult **stats,
> IndexVacuumInfo ivinfo;
> const char *msg;
> PGRUsage ru0;
> + ErrorContextCallback errcallback;
> + LVRelStats errcbarg; /* Used for error callback, only */
>
> pg_rusage_init(&ru0);
>
> @@ -2325,10 +2374,24 @@ lazy_vacuum_index(Relation indrel, IndexBulkDeleteResult **stats,
> ivinfo.num_heap_tuples = reltuples;
> ivinfo.strategy = vac_strategy;
>
> + /* Setup error traceback support for ereport() */
> + errcbarg.relnamespace = get_namespace_name(RelationGetNamespace(indrel));
> + errcbarg.indname = RelationGetRelationName(indrel);
> + errcbarg.relname = vacrelstats.relname;
> + errcbarg.stage = 2;
> +
> + errcallback.callback = vacuum_error_callback;
> + errcallback.arg = (void *) &errcbarg;
> + errcallback.previous = error_context_stack;
> + error_context_stack = &errcallback;
> +
> /* Do bulk deletion */
> *stats = index_bulk_delete(&ivinfo, *stats,
> lazy_tid_reaped, (void *) dead_tuples);
>
> + /* Pop the error context stack */
> + error_context_stack = errcallback.previous;
> +
> if (IsParallelWorker())
> msg = gettext_noop("scanned index \"%s\" to remove %d row versions by parallel vacuum worker");
> else
> @@ -3371,3 +3434,23 @@ parallel_vacuum_main(dsm_segment *seg, shm_toc *toc)
> table_close(onerel, ShareUpdateExclusiveLock);
> pfree(stats);
> }
> +
> +/*
> + * Error context callback for errors occurring during vacuum.
> + */
> +static void
> +vacuum_error_callback(void *arg)
> +{
> + LVRelStats *cbarg = arg;
> +
> + if (cbarg->stage == 0)
> + errcontext(_("while scanning block %u of relation \"%s.%s\""),
> + cbarg->blkno, cbarg->relnamespace, cbarg->relname);
> + else if (cbarg->stage == 1)
> + errcontext(_("while vacuuming block %u of relation \"%s.%s\""),
> + cbarg->blkno, cbarg->relnamespace, cbarg->relname);
> + else if (cbarg->stage == 2)
> + errcontext(_("while vacuuming index \"%s\" on table \"%s.%s\""),
> + cbarg->indname, cbarg->relnamespace, cbarg->relname);
> +
> +}
> --
> 2.7.4
>