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Rearrange dblink's dblink_build_sql_insert() and related routines to open and

lock the target relation just once per SQL function call.  The original coding
obtained and released lock several times per call.  Aside from saving a
not-insignificant number of cycles, this eliminates possible race conditions
if someone tries to modify the relation's schema concurrently.  Also
centralize locking and permission-checking logic.

Problem noted while investigating a trouble report from Robert Voinea --- his
problem is still to be fixed, though.
This commit is contained in:
Tom Lane 2010-06-14 20:49:46 +00:00
parent 644c2778d6
commit fa66d0e2da

View File

@ -8,7 +8,7 @@
* Darko Prenosil <Darko.Prenosil@finteh.hr>
* Shridhar Daithankar <shridhar_daithankar@persistent.co.in>
*
* $PostgreSQL: pgsql/contrib/dblink/dblink.c,v 1.69.2.5 2010/06/09 00:59:35 itagaki Exp $
* $PostgreSQL: pgsql/contrib/dblink/dblink.c,v 1.69.2.6 2010/06/14 20:49:46 tgl Exp $
* Copyright (c) 2001-2008, PostgreSQL Global Development Group
* ALL RIGHTS RESERVED;
*
@ -83,19 +83,19 @@ static remoteConn *getConnectionByName(const char *name);
static HTAB *createConnHash(void);
static void createNewConnection(const char *name, remoteConn * rconn);
static void deleteConnection(const char *name);
static char **get_pkey_attnames(Oid relid, int16 *numatts);
static char **get_pkey_attnames(Relation rel, int16 *numatts);
static char **get_text_array_contents(ArrayType *array, int *numitems);
static char *get_sql_insert(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pkattvals, char **tgt_pkattvals);
static char *get_sql_delete(Oid relid, int2vector *pkattnums, int16 pknumatts, char **tgt_pkattvals);
static char *get_sql_update(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pkattvals, char **tgt_pkattvals);
static char *get_sql_insert(Relation rel, int2vector *pkattnums, int16 pknumatts, char **src_pkattvals, char **tgt_pkattvals);
static char *get_sql_delete(Relation rel, int2vector *pkattnums, int16 pknumatts, char **tgt_pkattvals);
static char *get_sql_update(Relation rel, int2vector *pkattnums, int16 pknumatts, char **src_pkattvals, char **tgt_pkattvals);
static char *quote_literal_cstr(char *rawstr);
static char *quote_ident_cstr(char *rawstr);
static int16 get_attnum_pk_pos(int2vector *pkattnums, int16 pknumatts, int16 key);
static HeapTuple get_tuple_of_interest(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pkattvals);
static Oid get_relid_from_relname(text *relname_text);
static char *generate_relation_name(Oid relid);
static HeapTuple get_tuple_of_interest(Relation rel, int2vector *pkattnums, int16 pknumatts, char **src_pkattvals);
static Relation get_rel_from_relname(text *relname_text, LOCKMODE lockmode, AclMode aclmode);
static char *generate_relation_name(Relation rel);
static void dblink_security_check(PGconn *conn, remoteConn *rconn);
static int get_nondropped_natts(Oid relid);
static int get_nondropped_natts(Relation rel);
/* Global */
static remoteConn *pconn = NULL;
@ -1252,7 +1252,6 @@ Datum
dblink_get_pkey(PG_FUNCTION_ARGS)
{
int16 numatts;
Oid relid;
char **results;
FuncCallContext *funcctx;
int32 call_cntr;
@ -1263,7 +1262,8 @@ dblink_get_pkey(PG_FUNCTION_ARGS)
/* stuff done only on the first call of the function */
if (SRF_IS_FIRSTCALL())
{
TupleDesc tupdesc = NULL;
Relation rel;
TupleDesc tupdesc;
/* create a function context for cross-call persistence */
funcctx = SRF_FIRSTCALL_INIT();
@ -1273,13 +1273,13 @@ dblink_get_pkey(PG_FUNCTION_ARGS)
*/
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
/* convert relname to rel Oid */
relid = get_relid_from_relname(PG_GETARG_TEXT_P(0));
if (!OidIsValid(relid))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_TABLE),
errmsg("relation \"%s\" does not exist",
GET_STR(PG_GETARG_TEXT_P(0)))));
/* open target relation */
rel = get_rel_from_relname(PG_GETARG_TEXT_P(0), AccessShareLock, ACL_SELECT);
/* get the array of attnums */
results = get_pkey_attnames(rel, &numatts);
relation_close(rel, AccessShareLock);
/*
* need a tuple descriptor representing one INT and one TEXT column
@ -1297,9 +1297,6 @@ dblink_get_pkey(PG_FUNCTION_ARGS)
attinmeta = TupleDescGetAttInMetadata(tupdesc);
funcctx->attinmeta = attinmeta;
/* get an array of attnums */
results = get_pkey_attnames(relid, &numatts);
if ((results != NULL) && (numatts > 0))
{
funcctx->max_calls = numatts;
@ -1386,7 +1383,7 @@ dblink_build_sql_insert(PG_FUNCTION_ARGS)
int32 pknumatts_tmp = PG_GETARG_INT32(2);
ArrayType *src_pkattvals_arry = PG_GETARG_ARRAYTYPE_P(3);
ArrayType *tgt_pkattvals_arry = PG_GETARG_ARRAYTYPE_P(4);
Oid relid;
Relation rel;
int16 pknumatts = 0;
char **src_pkattvals;
char **tgt_pkattvals;
@ -1396,14 +1393,9 @@ dblink_build_sql_insert(PG_FUNCTION_ARGS)
int nondropped_natts;
/*
* Convert relname to rel OID.
* Open target relation.
*/
relid = get_relid_from_relname(relname_text);
if (!OidIsValid(relid))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_TABLE),
errmsg("relation \"%s\" does not exist",
GET_STR(relname_text))));
rel = get_rel_from_relname(relname_text, AccessShareLock, ACL_SELECT);
/*
* There should be at least one key attribute
@ -1425,7 +1417,7 @@ dblink_build_sql_insert(PG_FUNCTION_ARGS)
* ensure we don't ask for more pk attributes than we have
* non-dropped columns
*/
nondropped_natts = get_nondropped_natts(relid);
nondropped_natts = get_nondropped_natts(rel);
if (pknumatts > nondropped_natts)
ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR),
errmsg("number of primary key fields exceeds number of specified relation attributes")));
@ -1463,7 +1455,12 @@ dblink_build_sql_insert(PG_FUNCTION_ARGS)
/*
* Prep work is finally done. Go get the SQL string.
*/
sql = get_sql_insert(relid, pkattnums, pknumatts, src_pkattvals, tgt_pkattvals);
sql = get_sql_insert(rel, pkattnums, pknumatts, src_pkattvals, tgt_pkattvals);
/*
* Now we can close the relation.
*/
relation_close(rel, AccessShareLock);
/*
* And send it
@ -1496,21 +1493,16 @@ dblink_build_sql_delete(PG_FUNCTION_ARGS)
int32 pknumatts_tmp = PG_GETARG_INT32(2);
ArrayType *tgt_pkattvals_arry = PG_GETARG_ARRAYTYPE_P(3);
int nondropped_natts;
Oid relid;
Relation rel;
int16 pknumatts = 0;
char **tgt_pkattvals;
int tgt_nitems;
char *sql;
/*
* Convert relname to rel OID.
* Open target relation.
*/
relid = get_relid_from_relname(relname_text);
if (!OidIsValid(relid))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_TABLE),
errmsg("relation \"%s\" does not exist",
GET_STR(relname_text))));
rel = get_rel_from_relname(relname_text, AccessShareLock, ACL_SELECT);
/*
* There should be at least one key attribute
@ -1532,7 +1524,7 @@ dblink_build_sql_delete(PG_FUNCTION_ARGS)
* ensure we don't ask for more pk attributes than we have
* non-dropped columns
*/
nondropped_natts = get_nondropped_natts(relid);
nondropped_natts = get_nondropped_natts(rel);
if (pknumatts > nondropped_natts)
ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR),
errmsg("number of primary key fields exceeds number of specified relation attributes")));
@ -1555,7 +1547,12 @@ dblink_build_sql_delete(PG_FUNCTION_ARGS)
/*
* Prep work is finally done. Go get the SQL string.
*/
sql = get_sql_delete(relid, pkattnums, pknumatts, tgt_pkattvals);
sql = get_sql_delete(rel, pkattnums, pknumatts, tgt_pkattvals);
/*
* Now we can close the relation.
*/
relation_close(rel, AccessShareLock);
/*
* And send it
@ -1593,7 +1590,7 @@ dblink_build_sql_update(PG_FUNCTION_ARGS)
ArrayType *src_pkattvals_arry = PG_GETARG_ARRAYTYPE_P(3);
ArrayType *tgt_pkattvals_arry = PG_GETARG_ARRAYTYPE_P(4);
int nondropped_natts;
Oid relid;
Relation rel;
int16 pknumatts = 0;
char **src_pkattvals;
char **tgt_pkattvals;
@ -1602,14 +1599,9 @@ dblink_build_sql_update(PG_FUNCTION_ARGS)
char *sql;
/*
* Convert relname to rel OID.
* Open target relation.
*/
relid = get_relid_from_relname(relname_text);
if (!OidIsValid(relid))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_TABLE),
errmsg("relation \"%s\" does not exist",
GET_STR(relname_text))));
rel = get_rel_from_relname(relname_text, AccessShareLock, ACL_SELECT);
/*
* There should be one source array key values for each key attnum
@ -1631,7 +1623,7 @@ dblink_build_sql_update(PG_FUNCTION_ARGS)
* ensure we don't ask for more pk attributes than we have
* non-dropped columns
*/
nondropped_natts = get_nondropped_natts(relid);
nondropped_natts = get_nondropped_natts(rel);
if (pknumatts > nondropped_natts)
ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR),
errmsg("number of primary key fields exceeds number of specified relation attributes")));
@ -1669,7 +1661,12 @@ dblink_build_sql_update(PG_FUNCTION_ARGS)
/*
* Prep work is finally done. Go get the SQL string.
*/
sql = get_sql_update(relid, pkattnums, pknumatts, src_pkattvals, tgt_pkattvals);
sql = get_sql_update(rel, pkattnums, pknumatts, src_pkattvals, tgt_pkattvals);
/*
* Now we can close the relation.
*/
relation_close(rel, AccessShareLock);
/*
* And send it
@ -1706,7 +1703,7 @@ dblink_current_query(PG_FUNCTION_ARGS)
* Return NULL, and set numatts = 0, if no primary key exists.
*/
static char **
get_pkey_attnames(Oid relid, int16 *numatts)
get_pkey_attnames(Relation rel, int16 *numatts)
{
Relation indexRelation;
ScanKeyData skey;
@ -1714,22 +1711,11 @@ get_pkey_attnames(Oid relid, int16 *numatts)
HeapTuple indexTuple;
int i;
char **result = NULL;
Relation rel;
TupleDesc tupdesc;
AclResult aclresult;
/* initialize numatts to 0 in case no primary key exists */
*numatts = 0;
/* open relation using relid, check permissions, get tupdesc */
rel = relation_open(relid, AccessShareLock);
aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
ACL_SELECT);
if (aclresult != ACLCHECK_OK)
aclcheck_error(aclresult, ACL_KIND_CLASS,
RelationGetRelationName(rel));
tupdesc = rel->rd_att;
/* Prepare to scan pg_index for entries having indrelid = this rel. */
@ -1737,7 +1723,7 @@ get_pkey_attnames(Oid relid, int16 *numatts)
ScanKeyInit(&skey,
Anum_pg_index_indrelid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(relid));
ObjectIdGetDatum(RelationGetRelid(rel)));
scan = systable_beginscan(indexRelation, IndexIndrelidIndexId, true,
SnapshotNow, 1, &skey);
@ -1763,7 +1749,6 @@ get_pkey_attnames(Oid relid, int16 *numatts)
systable_endscan(scan);
heap_close(indexRelation, AccessShareLock);
relation_close(rel, AccessShareLock);
return result;
}
@ -1830,9 +1815,8 @@ get_text_array_contents(ArrayType *array, int *numitems)
}
static char *
get_sql_insert(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pkattvals, char **tgt_pkattvals)
get_sql_insert(Relation rel, int2vector *pkattnums, int16 pknumatts, char **src_pkattvals, char **tgt_pkattvals)
{
Relation rel;
char *relname;
HeapTuple tuple;
TupleDesc tupdesc;
@ -1846,16 +1830,12 @@ get_sql_insert(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pka
initStringInfo(&buf);
/* get relation name including any needed schema prefix and quoting */
relname = generate_relation_name(relid);
relname = generate_relation_name(rel);
/*
* Open relation using relid
*/
rel = relation_open(relid, AccessShareLock);
tupdesc = rel->rd_att;
natts = tupdesc->natts;
tuple = get_tuple_of_interest(relid, pkattnums, pknumatts, src_pkattvals);
tuple = get_tuple_of_interest(rel, pkattnums, pknumatts, src_pkattvals);
if (!tuple)
ereport(ERROR,
(errcode(ERRCODE_CARDINALITY_VIOLATION),
@ -1912,14 +1892,12 @@ get_sql_insert(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pka
}
appendStringInfo(&buf, ")");
relation_close(rel, AccessShareLock);
return (buf.data);
}
static char *
get_sql_delete(Oid relid, int2vector *pkattnums, int16 pknumatts, char **tgt_pkattvals)
get_sql_delete(Relation rel, int2vector *pkattnums, int16 pknumatts, char **tgt_pkattvals)
{
Relation rel;
char *relname;
TupleDesc tupdesc;
int natts;
@ -1929,12 +1907,8 @@ get_sql_delete(Oid relid, int2vector *pkattnums, int16 pknumatts, char **tgt_pka
initStringInfo(&buf);
/* get relation name including any needed schema prefix and quoting */
relname = generate_relation_name(relid);
relname = generate_relation_name(rel);
/*
* Open relation using relid
*/
rel = relation_open(relid, AccessShareLock);
tupdesc = rel->rd_att;
natts = tupdesc->natts;
@ -1960,14 +1934,12 @@ get_sql_delete(Oid relid, int2vector *pkattnums, int16 pknumatts, char **tgt_pka
appendStringInfo(&buf, " IS NULL");
}
relation_close(rel, AccessShareLock);
return (buf.data);
}
static char *
get_sql_update(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pkattvals, char **tgt_pkattvals)
get_sql_update(Relation rel, int2vector *pkattnums, int16 pknumatts, char **src_pkattvals, char **tgt_pkattvals)
{
Relation rel;
char *relname;
HeapTuple tuple;
TupleDesc tupdesc;
@ -1981,16 +1953,12 @@ get_sql_update(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pka
initStringInfo(&buf);
/* get relation name including any needed schema prefix and quoting */
relname = generate_relation_name(relid);
relname = generate_relation_name(rel);
/*
* Open relation using relid
*/
rel = relation_open(relid, AccessShareLock);
tupdesc = rel->rd_att;
natts = tupdesc->natts;
tuple = get_tuple_of_interest(relid, pkattnums, pknumatts, src_pkattvals);
tuple = get_tuple_of_interest(rel, pkattnums, pknumatts, src_pkattvals);
if (!tuple)
ereport(ERROR,
(errcode(ERRCODE_CARDINALITY_VIOLATION),
@ -2056,7 +2024,6 @@ get_sql_update(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pka
appendStringInfo(&buf, " IS NULL");
}
relation_close(rel, AccessShareLock);
return (buf.data);
}
@ -2112,9 +2079,8 @@ get_attnum_pk_pos(int2vector *pkattnums, int16 pknumatts, int16 key)
}
static HeapTuple
get_tuple_of_interest(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pkattvals)
get_tuple_of_interest(Relation rel, int2vector *pkattnums, int16 pknumatts, char **src_pkattvals)
{
Relation rel;
char *relname;
TupleDesc tupdesc;
StringInfoData buf;
@ -2125,14 +2091,9 @@ get_tuple_of_interest(Oid relid, int2vector *pkattnums, int16 pknumatts, char **
initStringInfo(&buf);
/* get relation name including any needed schema prefix and quoting */
relname = generate_relation_name(relid);
relname = generate_relation_name(rel);
/*
* Open relation using relid
*/
rel = relation_open(relid, AccessShareLock);
tupdesc = CreateTupleDescCopy(rel->rd_att);
relation_close(rel, AccessShareLock);
tupdesc = rel->rd_att;
/*
* Connect to SPI manager
@ -2203,52 +2164,49 @@ get_tuple_of_interest(Oid relid, int2vector *pkattnums, int16 pknumatts, char **
return NULL;
}
static Oid
get_relid_from_relname(text *relname_text)
/*
* Open the relation named by relname_text, acquire specified type of lock,
* verify we have specified permissions.
* Caller must close rel when done with it.
*/
static Relation
get_rel_from_relname(text *relname_text, LOCKMODE lockmode, AclMode aclmode)
{
RangeVar *relvar;
Relation rel;
Oid relid;
AclResult aclresult;
relvar = makeRangeVarFromNameList(textToQualifiedNameList(relname_text));
rel = heap_openrv(relvar, AccessShareLock);
relid = RelationGetRelid(rel);
relation_close(rel, AccessShareLock);
rel = heap_openrv(relvar, lockmode);
return relid;
aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
aclmode);
if (aclresult != ACLCHECK_OK)
aclcheck_error(aclresult, ACL_KIND_CLASS,
RelationGetRelationName(rel));
return rel;
}
/*
* generate_relation_name - copied from ruleutils.c
* Compute the name to display for a relation specified by OID
* Compute the name to display for a relation
*
* The result includes all necessary quoting and schema-prefixing.
*/
static char *
generate_relation_name(Oid relid)
generate_relation_name(Relation rel)
{
HeapTuple tp;
Form_pg_class reltup;
char *nspname;
char *result;
tp = SearchSysCache(RELOID,
ObjectIdGetDatum(relid),
0, 0, 0);
if (!HeapTupleIsValid(tp))
elog(ERROR, "cache lookup failed for relation %u", relid);
reltup = (Form_pg_class) GETSTRUCT(tp);
/* Qualify the name if not visible in search path */
if (RelationIsVisible(relid))
if (RelationIsVisible(RelationGetRelid(rel)))
nspname = NULL;
else
nspname = get_namespace_name(reltup->relnamespace);
nspname = get_namespace_name(rel->rd_rel->relnamespace);
result = quote_qualified_identifier(nspname, NameStr(reltup->relname));
ReleaseSysCache(tp);
result = quote_qualified_identifier(nspname, RelationGetRelationName(rel));
return result;
}
@ -2357,15 +2315,13 @@ dblink_security_check(PGconn *conn, remoteConn *rconn)
}
static int
get_nondropped_natts(Oid relid)
get_nondropped_natts(Relation rel)
{
int nondropped_natts = 0;
TupleDesc tupdesc;
Relation rel;
int natts;
int i;
rel = relation_open(relid, AccessShareLock);
tupdesc = rel->rd_att;
natts = tupdesc->natts;
@ -2376,7 +2332,6 @@ get_nondropped_natts(Oid relid)
nondropped_natts++;
}
relation_close(rel, AccessShareLock);
return nondropped_natts;
}