From 54a3b83f47e29181a061dea9d92f82c602bbdd2e Mon Sep 17 00:00:00 2001 From: Nik Samokhvalov Date: Thu, 8 Jan 2026 13:50:53 -0800 Subject: [PATCH] Add IO wait events for COPY file/program operations Add two new IO wait events: - COPY_DATA_READ: COPY FROM blocking on file or program read - COPY_DATA_WRITE: COPY TO blocking on file or program write This enables diagnosing: - Storage I/O bottlenecks during bulk loads (COPY FROM '/path/to/file') - Slow exports to files (COPY TO '/path/to/file') - Pipe buffer congestion in ETL pipelines (COPY FROM/TO PROGRAM) COPY FROM/TO STDIN/STDOUT already have coverage via Client/ClientRead and Client/ClientWrite at the protocol layer. These events are distinct from the existing COPY_FILE_READ/WRITE events, which instrument file-to-file copy operations in basebackup code. Example usage: -- Session 1: COPY large_table TO '/slow/nfs/mount/out.csv'; -- Session 2: SELECT wait_event, wait_event_type FROM pg_stat_activity WHERE pid = ; -- Shows: COPY_DATA_WRITE / IO --- src/backend/commands/copyfromparse.c | 2 ++ src/backend/commands/copyto.c | 2 ++ src/backend/utils/activity/wait_event_names.txt | 2 ++ 3 files changed, 6 insertions(+) diff --git a/src/backend/commands/copyfromparse.c b/src/backend/commands/copyfromparse.c index 5868a7fa11f..af1df0c1f14 100644 --- a/src/backend/commands/copyfromparse.c +++ b/src/backend/commands/copyfromparse.c @@ -249,7 +249,9 @@ CopyGetData(CopyFromState cstate, void *databuf, int minread, int maxread) switch (cstate->copy_src) { case COPY_FILE: + pgstat_report_wait_start(WAIT_EVENT_COPY_DATA_READ); bytesread = fread(databuf, 1, maxread, cstate->copy_file); + pgstat_report_wait_end(); if (ferror(cstate->copy_file)) ereport(ERROR, (errcode_for_file_access(), diff --git a/src/backend/commands/copyto.c b/src/backend/commands/copyto.c index 4ab4a3893d5..7d146e95b2d 100644 --- a/src/backend/commands/copyto.c +++ b/src/backend/commands/copyto.c @@ -454,6 +454,7 @@ CopySendEndOfRow(CopyToState cstate) switch (cstate->copy_dest) { case COPY_FILE: + pgstat_report_wait_start(WAIT_EVENT_COPY_DATA_WRITE); if (fwrite(fe_msgbuf->data, fe_msgbuf->len, 1, cstate->copy_file) != 1 || ferror(cstate->copy_file)) @@ -486,6 +487,7 @@ CopySendEndOfRow(CopyToState cstate) (errcode_for_file_access(), errmsg("could not write to COPY file: %m"))); } + pgstat_report_wait_end(); break; case COPY_FRONTEND: /* Dump the accumulated row as one CopyData message */ diff --git a/src/backend/utils/activity/wait_event_names.txt b/src/backend/utils/activity/wait_event_names.txt index 3299de23bb3..a7e4d5182a9 100644 --- a/src/backend/utils/activity/wait_event_names.txt +++ b/src/backend/utils/activity/wait_event_names.txt @@ -210,6 +210,8 @@ CONTROL_FILE_SYNC "Waiting for the pg_control file to reach CONTROL_FILE_SYNC_UPDATE "Waiting for an update to the pg_control file to reach durable storage." CONTROL_FILE_WRITE "Waiting for a write to the pg_control file." CONTROL_FILE_WRITE_UPDATE "Waiting for a write to update the pg_control file." +COPY_DATA_READ "Waiting for a read from a file or program during COPY FROM." +COPY_DATA_WRITE "Waiting for a write to a file or program during COPY TO." COPY_FILE_COPY "Waiting for a file copy operation." COPY_FILE_READ "Waiting for a read during a file copy operation." COPY_FILE_WRITE "Waiting for a write during a file copy operation." -- 2.50.1 (Apple Git-155)