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MXS-2409 Check that prepared statement exists

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If the PREPARE is malformed, the extracted statement is null.
This commit is contained in:
Esa Korhonen
2019-03-26 12:30:42 +02:00
parent a78f0fbe25
commit ee88180c54
2 changed files with 38 additions and 32 deletions
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9
Documentation/Routers/SchemaRouter.md
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@ -222,10 +222,11 @@ undefined. To work around this limitation, the query must be executed in separat
query will be routed to the first available server. This possibly returns an query will be routed to the first available server. This possibly returns an
error about database rights instead of a missing database. error about database rights instead of a missing database.
* The preparation of a prepared statement is routed to all servers. The * Prepared statement support is limited. PREPARE, EXECUTE and DEALLOCATE are routed to the
execution of a prepared statement is routed to the first available server or to correct backend if the statement is known and only requires one backend server. EXECUTE
the server pointed by a routing hint attached to the query. In practice this IMMEADIATE is not supported and is routed to the first available backend and may give
means that prepared statements aren't supported by the SchemaRouter. wrong results. Similarly, preparing a statement from a variable (e.g. `PREPARE stmt FROM
@a`) is not supported and may be routed wrong.
* `SHOW DATABASES` is handled by the router instead of routed to a server. The router only * `SHOW DATABASES` is handled by the router instead of routed to a server. The router only
answers correctly to the basic version of the query. Any modifiers such as `LIKE` are answers correctly to the basic version of the query. Any modifiers such as `LIKE` are

61
server/modules/routing/schemarouter/schemaroutersession.cc
View File

@ -1675,52 +1675,57 @@ SERVER* SchemaRouterSession::get_ps_target(GWBUF* buffer, uint32_t qtype, qc_que
if (qc_query_is_type(qtype, QUERY_TYPE_PREPARE_NAMED_STMT)) if (qc_query_is_type(qtype, QUERY_TYPE_PREPARE_NAMED_STMT))
{ {
// If pStmt is null, the PREPARE was malformed. In that case it can be routed to any backend to get
// a proper error response. Also returns null if preparing from a variable. This is a limitation.
GWBUF* pStmt = qc_get_preparable_stmt(buffer); GWBUF* pStmt = qc_get_preparable_stmt(buffer);
int n_tables = 0; if (pStmt)
char** tables = qc_get_table_names(pStmt, &n_tables, true);
char* stmt = qc_get_prepare_name(buffer);
for (int i = 0; i < n_tables; i++)
{ {
SERVER* target = m_shard.get_location(tables[i]); int n_tables = 0;
char** tables = qc_get_table_names(pStmt, &n_tables, true);
char* stmt = qc_get_prepare_name(buffer);
if (target) for (int i = 0; i < n_tables; i++)
{ {
SERVER* target = m_shard.get_location(tables[i]);
if (rval && target != rval) if (target)
{ {
MXS_ERROR("Statement targets tables on servers '%s' and '%s'. " if (rval && target != rval)
"Cross server queries are not supported.", {
rval->name, MXS_ERROR("Statement targets tables on servers '%s' and '%s'. "
target->name); "Cross server queries are not supported.",
} rval->name, target->name);
else if (rval == NULL) }
{ else if (rval == NULL)
rval = target; {
rval = target;
}
} }
MXS_FREE(tables[i]);
} }
MXS_FREE(tables[i]);
}
if (rval) if (rval)
{ {
MXS_INFO("PREPARING NAMED %s ON SERVER %s", stmt, rval->name); MXS_INFO("PREPARING NAMED %s ON SERVER %s", stmt, rval->name);
m_shard.add_statement(stmt, rval); m_shard.add_statement(stmt, rval);
}
MXS_FREE(tables);
MXS_FREE(stmt);
} }
MXS_FREE(tables);
MXS_FREE(stmt);
} }
else if (op == QUERY_OP_EXECUTE) else if (op == QUERY_OP_EXECUTE)
{ {
char* stmt = qc_get_prepare_name(buffer); char* stmt = qc_get_prepare_name(buffer);
rval = m_shard.get_statement(stmt); SERVER* ps_target = m_shard.get_statement(stmt);
MXS_INFO("Executing named statement %s on server %s", stmt, rval->name); if (ps_target)
{
rval = ps_target;
MXS_INFO("Executing named statement %s on server %s", stmt, rval->name);
}
MXS_FREE(stmt); MXS_FREE(stmt);
} }
else if (qc_query_is_type(qtype, QUERY_TYPE_DEALLOC_PREPARE)) else if (qc_query_is_type(qtype, QUERY_TYPE_DEALLOC_PREPARE))
{ {
char* stmt = qc_get_prepare_name(buffer); char* stmt = qc_get_prepare_name(buffer);
if ((rval = m_shard.get_statement(stmt))) if ((rval = m_shard.get_statement(stmt)))
{ {
MXS_INFO("Closing named statement %s on server %s", stmt, rval->name); MXS_INFO("Closing named statement %s on server %s", stmt, rval->name);