git.postgresql.org Git - postgresql.git/commitdiff

git projects / postgresql.git / commitdiff

Cache the results of format_type() queries in pg_dump.

2021年8月31日 17:53:33 +0000 (13:53 -0400)

2021年8月31日 17:53:49 +0000 (13:53 -0400)

There's long been a "TODO: there might be some value in caching
the results" annotation on pg_dump's getFormattedTypeName function;
but we hadn't gotten around to checking what it was costing us to
repetitively look up type names. It turns out that when dumping the
current regression database, about 10% of the total number of queries
issued are duplicative format_type() queries. However, Hubert Depesz
Lubaczewski reported a not-unusual case where these account for over
half of the queries issued by pg_dump. Individually these queries
aren't expensive, but when network lag is a factor, they add up to a
problem. We can very easily add some caching to getFormattedTypeName
to solve it.

Since this is such a simple fix and can have a visible performance
benefit, back-patch to all supported branches.

Discussion: https://postgr.es/m/20210826084430.GA26282@depesz.com

src/bin/pg_dump/pg_dump.c patch | blob | blame | history

src/bin/pg_dump/pg_dump.h patch | blob | blame | history

diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c

index 6adbd20778d3f9e87662fbac5798f39943415495..6259e68aa4bc9b7cba9f95d5e4835922ce7436eb 100644 (file)

--- a/src/bin/pg_dump/pg_dump.c

+++ b/src/bin/pg_dump/pg_dump.c

@@ -5232,6 +5232,7 @@ getTypes(Archive *fout, int *numTypes)

tyinfo[i].dobj.name = pg_strdup(PQgetvalue(res, i, i_typname));

tyinfo[i].dobj.namespace =

findNamespace(atooid(PQgetvalue(res, i, i_typnamespace)));

+ tyinfo[i].ftypname = NULL; /* may get filled later */

tyinfo[i].rolname = pg_strdup(PQgetvalue(res, i, i_rolname));

tyinfo[i].typacl = pg_strdup(PQgetvalue(res, i, i_typacl));

tyinfo[i].rtypacl = pg_strdup(PQgetvalue(res, i, i_rtypacl));

@@ -18892,12 +18893,11 @@ findDumpableDependencies(ArchiveHandle *AH, const DumpableObject *dobj,

* This does not guarantee to schema-qualify the output, so it should not

* be used to create the target object name for CREATE or ALTER commands.

- *

- * TODO: there might be some value in caching the results.

static char *

getFormattedTypeName(Archive *fout, Oid oid, OidOptions opts)

{

+ TypeInfo *typeInfo;

char *result;

PQExpBuffer query;

PGresult *res;

@@ -18910,6 +18910,11 @@ getFormattedTypeName(Archive *fout, Oid oid, OidOptions opts)

return pg_strdup("NONE");

}

+ /* see if we have the result cached in the type's TypeInfo record */

+ typeInfo = findTypeByOid(oid);

+ if (typeInfo && typeInfo->ftypname)

+ return pg_strdup(typeInfo->ftypname);

query = createPQExpBuffer();

appendPQExpBuffer(query, "SELECT pg_catalog.format_type('%u'::pg_catalog.oid, NULL)",

oid);

@@ -18922,6 +18927,10 @@ getFormattedTypeName(Archive *fout, Oid oid, OidOptions opts)

PQclear(res);

destroyPQExpBuffer(query);

+ /* cache a copy for later requests */

+ if (typeInfo)

+ typeInfo->ftypname = pg_strdup(result);

return result;

}

diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h

index f5e170e0dbc26da1d500c53fc98ac1697f3472b0..29af845ece6894f9fe677f0f7f50e4646ff8e99f 100644 (file)

--- a/src/bin/pg_dump/pg_dump.h

+++ b/src/bin/pg_dump/pg_dump.h

@@ -166,9 +166,11 @@ typedef struct _typeInfo

DumpableObject dobj;

- * Note: dobj.name is the pg_type.typname entry. format_type() might

- * produce something different than typname

+ * Note: dobj.name is the raw pg_type.typname entry. ftypname is the

+ * result of format_type(), which will be quoted if needed, and might be

+ * schema-qualified too.

+ char *ftypname;

char *rolname; /* name of owner, or empty string */

char *typacl;

char *rtypacl;

This is the main PostgreSQL git repository.

RSS Atom