Hello,
We (Neon) have noticed that pgbench can be quite slow to populate data
in regard to higher latency connections. Higher scale factors exacerbate
this problem. Some employees work on a different continent than the
databases they might be benchmarking. By moving pgbench to use COPY for
populating all tables, we can reduce some of the time pgbench takes for
this particular step.
I wanted to come with benchmarks, but unfortunately I won't have them
until next month. I can follow-up in a future email.
--
Tristan Partin
Neon (https://neon.tech)
From 498f5c7fddceafed3f831963dfca12256746390c Mon Sep 17 00:00:00 2001
From: Tristan Partin <tris...@neon.tech>
Date: Tue, 23 May 2023 09:21:55 -0500
Subject: [PATCH postgres v1 1/2] Move constant into format string
If we are always going to write a 0, just put the 0 in the format
string.
---
src/bin/pgbench/pgbench.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/src/bin/pgbench/pgbench.c b/src/bin/pgbench/pgbench.c
index 70ed034e70..0fbb9a2616 100644
--- a/src/bin/pgbench/pgbench.c
+++ b/src/bin/pgbench/pgbench.c
@@ -4939,8 +4939,8 @@ initGenerateDataClientSide(PGconn *con)
/* "filler" column defaults to blank padded empty string */
printfPQExpBuffer(&sql,
- INT64_FORMAT "\t" INT64_FORMAT "\t%d\t\n",
- j, k / naccounts + 1, 0);
+ INT64_FORMAT "\t" INT64_FORMAT "\t0\t\n",
+ j, k / naccounts + 1);
if (PQputline(con, sql.data))
pg_fatal("PQputline failed");
--
--
Tristan Partin
Neon (https://neon.tech)
From 6a326d6e3197142ee03140679ebedc978ee1485c Mon Sep 17 00:00:00 2001
From: Tristan Partin <tris...@neon.tech>
Date: Tue, 23 May 2023 11:48:16 -0500
Subject: [PATCH postgres v1 2/2] Use COPY instead of INSERT for populating all
tables
COPY is a better interface for bulk loading and/or high latency
connections. Previously COPY was only used for the pgbench_accounts
table because the amount of data was so much larger than the other
tables. However, as already said there are also gains to be had in the
high latency case, such as loading data across continents.
---
src/bin/pgbench/pgbench.c | 152 ++++++++++++++++++++++----------------
1 file changed, 88 insertions(+), 64 deletions(-)
diff --git a/src/bin/pgbench/pgbench.c b/src/bin/pgbench/pgbench.c
index 0fbb9a2616..6c7f143e86 100644
--- a/src/bin/pgbench/pgbench.c
+++ b/src/bin/pgbench/pgbench.c
@@ -4861,17 +4861,46 @@ initTruncateTables(PGconn *con)
"pgbench_tellers");
}
-/*
- * Fill the standard tables with some data generated and sent from the client
- */
+typedef void initRow(PGconn *con, PQExpBufferData *sql, int64 curr);
+
static void
-initGenerateDataClientSide(PGconn *con)
+initBranch(PGconn *con, PQExpBufferData *sql, int64 curr)
{
- PQExpBufferData sql;
+ /* "filler" column defaults to NULL */
+ printfPQExpBuffer(sql,
+ INT64_FORMAT "\t0\t\n",
+ curr + 1);
+}
+
+static void
+initTeller(PGconn *con, PQExpBufferData *sql, int64 curr)
+{
+ /* "filler" column defaults to NULL */
+ printfPQExpBuffer(sql,
+ INT64_FORMAT "\t" INT64_FORMAT "\t0\t\n",
+ curr + 1, curr / ntellers + 1);
+}
+
+static void
+initAccount(PGconn *con, PQExpBufferData *sql, int64 curr)
+{
+ /* "filler" column defaults to blank padded empty string */
+ printfPQExpBuffer(sql,
+ INT64_FORMAT "\t" INT64_FORMAT "\t0\t\n",
+ curr + 1, curr / naccounts + 1);
+}
+
+static void
+initPopulateTable(PGconn *con, const char *table, int64 base, initRow *init_row)
+{
+ int n;
+ int64 k;
PGresult *res;
- int i;
- int64 k;
- char *copy_statement;
+ PQExpBufferData sql;
+ bool printed = false;
+ char copy_statement[256];
+ const char *copy_statement_fmt;
+ const int64 total = base * scale;
/* used to track elapsed time and estimate of the remaining time */
pg_time_usec_t start;
@@ -4880,50 +4909,19 @@ initGenerateDataClientSide(PGconn *con)
/* Stay on the same line if reporting to a terminal */
char eol = isatty(fileno(stderr)) ? '\r' : '\n';
- fprintf(stderr, "generating data (client-side)...\n");
-
- /*
- * we do all of this in one transaction to enable the backend's
- * data-loading optimizations
- */
- executeStatement(con, "begin");
-
- /* truncate away any old data */
- initTruncateTables(con);
-
initPQExpBuffer(&sql);
- /*
- * fill branches, tellers, accounts in that order in case foreign keys
- * already exist
- */
- for (i = 0; i < nbranches * scale; i++)
- {
- /* "filler" column defaults to NULL */
- printfPQExpBuffer(&sql,
- "insert into pgbench_branches(bid,bbalance) values(%d,0)",
- i + 1);
- executeStatement(con, sql.data);
- }
-
- for (i = 0; i < ntellers * scale; i++)
- {
- /* "filler" column defaults to NULL */
- printfPQExpBuffer(&sql,
- "insert into pgbench_tellers(tid,bid,tbalance) values (%d,%d,0)",
- i + 1, i / ntellers + 1);
- executeStatement(con, sql.data);
- }
-
- /*
- * accounts is big enough to be worth using COPY and tracking runtime
- */
-
/* use COPY with FREEZE on v14 and later without partitioning */
if (partitions == 0 && PQserverVersion(con) >= 140000)
- copy_statement = "copy pgbench_accounts from stdin with (freeze on)";
+ copy_statement_fmt = "copy %s from stdin with (freeze on)";
else
- copy_statement = "copy pgbench_accounts from stdin";
+ copy_statement_fmt = "copy %s from stdin";
+
+ n = pg_snprintf(copy_statement, sizeof(copy_statement), copy_statement_fmt, table);
+ if (n >= sizeof(copy_statement))
+ pg_fatal("invalid buffer size: must be at least %d characters long", n);
+ else if (n == -1)
+ pg_fatal("invalid format string");
res = PQexec(con, copy_statement);
@@ -4933,14 +4931,11 @@ initGenerateDataClientSide(PGconn *con)
start = pg_time_now();
- for (k = 0; k < (int64) naccounts * scale; k++)
+ for (k = 0; k < total; k++)
{
- int64 j = k + 1;
+ const int64 j = k + 1;
- /* "filler" column defaults to blank padded empty string */
- printfPQExpBuffer(&sql,
- INT64_FORMAT "\t" INT64_FORMAT "\t0\t\n",
- j, k / naccounts + 1);
+ init_row(con, &sql, k);
if (PQputline(con, sql.data))
pg_fatal("PQputline failed");
@@ -4954,25 +4949,28 @@ initGenerateDataClientSide(PGconn *con)
if ((!use_quiet) && (j % 100000 == 0))
{
double elapsed_sec = PG_TIME_GET_DOUBLE(pg_time_now() - start);
- double remaining_sec = ((double) scale * naccounts - j) * elapsed_sec / j;
+ double remaining_sec = ((double) total - j) * elapsed_sec / j;
- fprintf(stderr, INT64_FORMAT " of " INT64_FORMAT " tuples (%d%%) done (elapsed %.2f s, remaining %.2f s)%c",
- j, (int64) naccounts * scale,
- (int) (((int64) j * 100) / (naccounts * (int64) scale)),
- elapsed_sec, remaining_sec, eol);
+ printed = true;
+ fprintf(stderr, INT64_FORMAT " of " INT64_FORMAT " tuples (%d%%) of %s done (elapsed %.2f s, remaining %.2f s)%c",
+ j, total,
+ (int) ((j * 100) / total),
+ table, elapsed_sec, remaining_sec, eol);
}
/* let's not call the timing for each row, but only each 100 rows */
else if (use_quiet && (j % 100 == 0))
{
double elapsed_sec = PG_TIME_GET_DOUBLE(pg_time_now() - start);
- double remaining_sec = ((double) scale * naccounts - j) * elapsed_sec / j;
+ double remaining_sec = ((double) total - j) * elapsed_sec / j;
/* have we reached the next interval (or end)? */
- if ((j == scale * naccounts) || (elapsed_sec >= log_interval * LOG_STEP_SECONDS))
+ if ((j == total) || (elapsed_sec >= log_interval * LOG_STEP_SECONDS))
{
- fprintf(stderr, INT64_FORMAT " of " INT64_FORMAT " tuples (%d%%) done (elapsed %.2f s, remaining %.2f s)%c",
- j, (int64) naccounts * scale,
- (int) (((int64) j * 100) / (naccounts * (int64) scale)), elapsed_sec, remaining_sec, eol);
+ printed = true;
+ fprintf(stderr, INT64_FORMAT " of " INT64_FORMAT " tuples (%d%%) of %s done (elapsed %.2f s, remaining %.2f s)%c",
+ j, total,
+ (int) ((j * 100) / total),
+ table, elapsed_sec, remaining_sec, eol);
/* skip to the next interval */
log_interval = (int) ceil(elapsed_sec / LOG_STEP_SECONDS);
@@ -4980,7 +4978,7 @@ initGenerateDataClientSide(PGconn *con)
}
}
- if (eol != '\n')
+ if (printed && eol != '\n')
fputc('\n', stderr); /* Need to move to next line */
if (PQputline(con, "\\.\n"))
@@ -4989,6 +4987,32 @@ initGenerateDataClientSide(PGconn *con)
pg_fatal("PQendcopy failed");
termPQExpBuffer(&sql);
+}
+
+/*
+ * Fill the standard tables with some data generated and sent from the client
+ */
+static void
+initGenerateDataClientSide(PGconn *con)
+{
+ fprintf(stderr, "generating data (client-side)...\n");
+
+ /*
+ * we do all of this in one transaction to enable the backend's
+ * data-loading optimizations
+ */
+ executeStatement(con, "begin");
+
+ /* truncate away any old data */
+ initTruncateTables(con);
+
+ /*
+ * fill branches, tellers, accounts in that order in case foreign keys
+ * already exist
+ */
+ initPopulateTable(con, "pgbench_branches", nbranches, initBranch);
+ initPopulateTable(con, "pgbench_tellers", ntellers, initTeller);
+ initPopulateTable(con, "pgbench_accounts", naccounts, initAccount);
executeStatement(con, "commit");
}
--
--
Tristan Partin
Neon (https://neon.tech)
