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Rewrite pg_dump's comment-dumping code to pull over all the comments

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in one query, rather than making a separate query for each object that
could have a comment.  This costs relatively little space (a few tens of
K typically) and saves substantial time in databases with many objects.
I find it reduces the runtime of 'pg_dump -s regression' by about a
third.
REL8_0_STABLE
Tom Lane 22 years ago
parent c8aaa5ceec
commit 05649b88c7
1 changed files with 215 additions and 93 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 308
      src/bin/pg_dump/pg_dump.c

308
src/bin/pg_dump/pg_dump.c
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@ -12,7 +12,7 @@
* by PostgreSQL
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/bin/pg_dump/pg_dump.c,v 1.367 2004/03/03 21:28:54 tgl Exp $
* $PostgreSQL: pgsql/src/bin/pg_dump/pg_dump.c,v 1.368 2004/03/20 20:09:45 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -67,6 +67,15 @@ extern int optind,
opterr;
typedef struct
{
const char *descr; /* comment for an object */
Oid classoid; /* object class (catalog OID) */
Oid objoid; /* object OID */
int objsubid; /* subobject (table column #) */
} CommentItem;
/* global decls */
bool g_verbose; /* User wants verbose narration of our
* activities. */
@ -105,6 +114,9 @@ static void dumpTableData(Archive *fout, TableDataInfo *tdinfo);
static void dumpComment(Archive *fout, const char *target,
const char *namespace, const char *owner,
CatalogId catalogId, int subid, DumpId dumpId);
static int findComments(Archive *fout, Oid classoid, Oid objoid,
CommentItem **items);
static int collectComments(Archive *fout, CommentItem **items);
static void dumpDumpableObject(Archive *fout, DumpableObject *dobj);
static void dumpNamespace(Archive *fout, NamespaceInfo *nspinfo);
static void dumpType(Archive *fout, TypeInfo *tinfo);
@ -3880,58 +3892,33 @@ dumpComment(Archive *fout, const char *target,
const char *namespace, const char *owner,
CatalogId catalogId, int subid, DumpId dumpId)
{
PGresult *res;
PQExpBuffer query;
int i_description;
CommentItem *comments;
int ncomments;
/* Comments are SCHEMA not data */
if (dataOnly)
return;
/*
* Note we do NOT change source schema here; preserve the caller's
* setting, instead.
*/
/* Search for comments associated with catalogId, using table */
ncomments = findComments(fout, catalogId.tableoid, catalogId.oid,
&comments);
/* Build query to find comment */
query = createPQExpBuffer();
if (fout->remoteVersion >= 70300)
{
appendPQExpBuffer(query,
"SELECT description FROM pg_catalog.pg_description "
"WHERE classoid = '%u'::pg_catalog.oid and "
"objoid = '%u'::pg_catalog.oid and objsubid = %d",
catalogId.tableoid, catalogId.oid, subid);
}
else if (fout->remoteVersion >= 70200)
{
appendPQExpBuffer(query,
"SELECT description FROM pg_description "
"WHERE classoid = '%u'::oid and "
"objoid = '%u'::oid and objsubid = %d",
catalogId.tableoid, catalogId.oid, subid);
}
else
/* Is there one matching the subid? */
while (ncomments > 0)
{
/* Note: this will fail to find attribute comments in pre-7.2... */
appendPQExpBuffer(query, "SELECT description FROM pg_description WHERE objoid = '%u'::oid", catalogId.oid);
if (comments->objsubid == subid)
break;
comments++;
ncomments--;
}
/* Execute query */
res = PQexec(g_conn, query->data);
check_sql_result(res, g_conn, query->data, PGRES_TUPLES_OK);
/* If a comment exists, build COMMENT ON statement */
if (PQntuples(res) == 1)
if (ncomments > 0)
{
i_description = PQfnumber(res, "description");
resetPQExpBuffer(query);
PQExpBuffer query = createPQExpBuffer();
appendPQExpBuffer(query, "COMMENT ON %s IS ", target);
appendStringLiteral(query, PQgetvalue(res, 0, i_description), false);
appendStringLiteral(query, comments->descr, false);
appendPQExpBuffer(query, ";\n");
ArchiveEntry(fout, nilCatalogId, createDumpId(),
@ -3939,82 +3926,47 @@ dumpComment(Archive *fout, const char *target,
"COMMENT", query->data, "", NULL,
&(dumpId), 1,
NULL, NULL);
}
PQclear(res);
destroyPQExpBuffer(query);
destroyPQExpBuffer(query);
}
}
/*
* dumpTableComment --
*
* As above, but dump comments for both the specified table (or view)
* and its columns. For speed, we want to do this with only one query.
* and its columns.
*/
static void
dumpTableComment(Archive *fout, TableInfo *tbinfo,
const char *reltypename)
{
PGresult *res;
CommentItem *comments;
int ncomments;
PQExpBuffer query;
PQExpBuffer target;
int i_description;
int i_objsubid;
int ntups;
int i;
/* Comments are SCHEMA not data */
if (dataOnly)
return;
/*
* Note we do NOT change source schema here; preserve the caller's
* setting, instead.
*/
/* Search for comments associated with relation, using table */
ncomments = findComments(fout,
tbinfo->dobj.catId.tableoid,
tbinfo->dobj.catId.oid,
&comments);
/* Build query to find comments */
/* If comments exist, build COMMENT ON statements */
if (ncomments <= 0)
return;
query = createPQExpBuffer();
target = createPQExpBuffer();
if (fout->remoteVersion >= 70300)
{
appendPQExpBuffer(query, "SELECT description, objsubid FROM pg_catalog.pg_description "
"WHERE classoid = '%u'::pg_catalog.oid and "
"objoid = '%u'::pg_catalog.oid "
"ORDER BY objoid, classoid, objsubid",
tbinfo->dobj.catId.tableoid, tbinfo->dobj.catId.oid);
}
else if (fout->remoteVersion >= 70200)
{
appendPQExpBuffer(query, "SELECT description, objsubid FROM pg_description "
"WHERE classoid = '%u'::oid and "
"objoid = '%u'::oid "
"ORDER BY objoid, classoid, objsubid",
tbinfo->dobj.catId.tableoid, tbinfo->dobj.catId.oid);
}
else
{
/* Note: this will fail to find attribute comments in pre-7.2... */
appendPQExpBuffer(query, "SELECT description, 0 as objsubid FROM pg_description WHERE objoid = '%u'::oid",
tbinfo->dobj.catId.oid);
}
/* Execute query */
res = PQexec(g_conn, query->data);
check_sql_result(res, g_conn, query->data, PGRES_TUPLES_OK);
i_description = PQfnumber(res, "description");
i_objsubid = PQfnumber(res, "objsubid");
/* If comments exist, build COMMENT ON statements */
ntups = PQntuples(res);
for (i = 0; i < ntups; i++)
while (ncomments > 0)
{
const char *descr = PQgetvalue(res, i, i_description);
int objsubid = atoi(PQgetvalue(res, i, i_objsubid));
const char *descr = comments->descr;
int objsubid = comments->objsubid;
if (objsubid == 0)
{
@ -4054,13 +4006,183 @@ dumpTableComment(Archive *fout, TableInfo *tbinfo,
&(tbinfo->dobj.dumpId), 1,
NULL, NULL);
}
comments++;
ncomments--;
}
PQclear(res);
destroyPQExpBuffer(query);
destroyPQExpBuffer(target);
}
/*
* findComments --
*
* Find the comment(s), if any, associated with the given object. All the
* objsubid values associated with the given classoid/objoid are found with
* one search.
*/
static int
findComments(Archive *fout, Oid classoid, Oid objoid,
CommentItem **items)
{
/* static storage for table of comments */
static CommentItem *comments = NULL;
static int ncomments = -1;
CommentItem *middle = NULL;
CommentItem *low;
CommentItem *high;
int nmatch;
/* Get comments if we didn't already */
if (ncomments < 0)
ncomments = collectComments(fout, &comments);
/*
* Pre-7.2, pg_description does not contain classoid, so collectComments
* just stores a zero. If there's a collision on object OID, well, you
* get duplicate comments.
*/
if (fout->remoteVersion < 70200)
classoid = 0;
/*
* Do binary search to find some item matching the object.
*/
low = &comments[0];
high = &comments[ncomments-1];
while (low <= high)
{
middle = low + (high - low) / 2;
if (classoid < middle->classoid)
high = middle - 1;
else if (classoid > middle->classoid)
low = middle + 1;
else if (objoid < middle->objoid)
high = middle - 1;
else if (objoid > middle->objoid)
low = middle + 1;
else
break; /* found a match */
}
if (low > high) /* no matches */
{
*items = NULL;
return 0;
}
/*
* Now determine how many items match the object. The search loop
* invariant still holds: only items between low and high inclusive
* could match.
*/
nmatch = 1;
while (middle > low)
{
if (classoid != middle[-1].classoid ||
objoid != middle[-1].objoid)
break;
middle--;
nmatch++;
}
*items = middle;
middle += nmatch;
while (middle <= high)
{
if (classoid != middle->classoid ||
objoid != middle->objoid)
break;
middle++;
nmatch++;
}
return nmatch;
}
/*
* collectComments --
*
* Construct a table of all comments available for database objects.
* We used to do per-object queries for the comments, but it's much faster
* to pull them all over at once, and on most databases the memory cost
* isn't high.
*
* The table is sorted by classoid/objid/objsubid for speed in lookup.
*/
static int
collectComments(Archive *fout, CommentItem **items)
{
PGresult *res;
PQExpBuffer query;
int i_description;
int i_classoid;
int i_objoid;
int i_objsubid;
int ntups;
int i;
CommentItem *comments;
/*
* Note we do NOT change source schema here; preserve the caller's
* setting, instead.
*/
query = createPQExpBuffer();
if (fout->remoteVersion >= 70300)
{
appendPQExpBuffer(query, "SELECT description, classoid, objoid, objsubid "
"FROM pg_catalog.pg_description "
"ORDER BY classoid, objoid, objsubid");
}
else if (fout->remoteVersion >= 70200)
{
appendPQExpBuffer(query, "SELECT description, classoid, objoid, objsubid "
"FROM pg_description "
"ORDER BY classoid, objoid, objsubid");
}
else
{
/* Note: this will fail to find attribute comments in pre-7.2... */
appendPQExpBuffer(query, "SELECT description, 0 as classoid, objoid, 0 as objsubid "
"FROM pg_description "
"ORDER BY objoid");
}
res = PQexec(g_conn, query->data);
check_sql_result(res, g_conn, query->data, PGRES_TUPLES_OK);
/* Construct lookup table containing OIDs in numeric form */
i_description = PQfnumber(res, "description");
i_classoid = PQfnumber(res, "classoid");
i_objoid = PQfnumber(res, "objoid");
i_objsubid = PQfnumber(res, "objsubid");
ntups = PQntuples(res);
comments = (CommentItem *) malloc(ntups * sizeof(CommentItem));
for (i = 0; i < ntups; i++)
{
comments[i].descr = PQgetvalue(res, i, i_description);
comments[i].classoid = atooid(PQgetvalue(res, i, i_classoid));
comments[i].objoid = atooid(PQgetvalue(res, i, i_objoid));
comments[i].objsubid = atoi(PQgetvalue(res, i, i_objsubid));
}
/* Do NOT free the PGresult since we are keeping pointers into it */
destroyPQExpBuffer(query);
*items = comments;
return ntups;
}
/*
* dumpDumpableObject
*

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