Fix query cache invalidation bug.

When a DML is executed in an explicit transaction, the table oid
buffer is wiped out by pool_reset_memqcache_buffer() and query cache
is not invalidated at the commit time because there's no DML oid
exists to invalidate query cache any more. To fix this, add new bool
parameter to pool_reset_memqcache_buffer() to specify whether to reset
table oid buffer or not. When a DML is executed in an explicit
transaction, call pool_reset_memqcache_buffer(false) to preserve the
table oid buffer.

Issue reported at https://github.com/pgpool/pgpool2/issues/19.

diff --git a/src/query_cache/pool_memqcache.c b/src/query_cache/pool_memqcache.c
index 7ab71bebf1c6ba8da89da2500bae852083f47a90..1f99e853a0a7fd5b451c55448a37eb23ed38c547 100644 (file)
--- a/src/query_cache/pool_memqcache.c
+++ b/src/query_cache/pool_memqcache.c
@@ -75,9 +75,10 @@ static int pool_get_dml_table_oid(int **oid);
 static int pool_get_dropdb_table_oids(int **oids, int dboid);
 static void pool_discard_dml_table_oid(void);
 static void pool_invalidate_query_cache(int num_table_oids, int *table_oid, bool unlink, int dboid);
+
 static int pool_get_database_oid(void);
 static void pool_add_table_oid_map(POOL_CACHEKEY *cachkey, int num_table_oids, int *table_oids);
-static void pool_reset_memqcache_buffer(void);
+static void pool_reset_memqcache_buffer(bool reset_dml_oids);
 static POOL_CACHEID *pool_add_item_shmem_cache(POOL_QUERY_HASH *query_hash, char *data, int size);
 static POOL_CACHEID *pool_find_item_on_shmem_cache(POOL_QUERY_HASH *query_hash);
 static char *pool_get_item_shmem_cache(POOL_QUERY_HASH *query_hash, int *size, int *sts);
@@ -1634,9 +1635,10 @@ static void pool_invalidate_query_cache(int num_table_oids, int *table_oid, bool
 }
 
 /*
- * Reset SELECT data buffers
+ * Reset SELECT data buffers.  If reset_dml_oids is true, call
+ * pool_discard_dml_table_oid() to reset table oids used in DML statements.
  */
-static void pool_reset_memqcache_buffer(void)
+static void pool_reset_memqcache_buffer(bool reset_dml_oids)
 {
        POOL_SESSION_CONTEXT * session_context;
 
@@ -1676,7 +1678,10 @@ static void pool_reset_memqcache_buffer(void)
                        session_context->query_context->temp_cache = NULL;
                }
        }
-       pool_discard_dml_table_oid();
+
+       if (reset_dml_oids)
+               pool_discard_dml_table_oid();
+
        pool_tmp_stats_reset_num_selects();
 }
 
@@ -3167,7 +3172,7 @@ void pool_handle_query_cache(POOL_CONNECTION_POOL *backend, char *query, Node *n
                        pool_stats_count_up_num_selects(1);
 
                        /* Reset temp buffer */
-                       pool_reset_memqcache_buffer();
+                       pool_reset_memqcache_buffer(true);
                }
                else
                {
@@ -3219,7 +3224,7 @@ void pool_handle_query_cache(POOL_CONNECTION_POOL *backend, char *query, Node *n
        else if (is_rollback_query(node))       /* Rollback? */
        {
                /* Discard buffered data */
-               pool_reset_memqcache_buffer();
+               pool_reset_memqcache_buffer(true);
        }
        else if (is_commit_query(node))         /* Commit? */
        {
@@ -3271,7 +3276,7 @@ void pool_handle_query_cache(POOL_CONNECTION_POOL *backend, char *query, Node *n
                /* Count up number of SELECT stats */
                pool_stats_count_up_num_selects(pool_tmp_stats_get_num_selects());
 
-               pool_reset_memqcache_buffer();
+               pool_reset_memqcache_buffer(true);
        }
        else            /* Non cache safe queries */
        {
@@ -3282,7 +3287,7 @@ void pool_handle_query_cache(POOL_CONNECTION_POOL *backend, char *query, Node *n
                        {
                                /* Count up SELECT stats */
                                pool_stats_count_up_num_selects(1);
-                               pool_reset_memqcache_buffer();
+                               pool_reset_memqcache_buffer(true);
                        }
                        else
                        {
@@ -3305,7 +3310,7 @@ void pool_handle_query_cache(POOL_CONNECTION_POOL *backend, char *query, Node *n
                                pool_invalidate_query_cache(num_oids, oids, true, dboid);
                                pool_discard_oid_maps_by_db(dboid);
                                pool_shmem_unlock();
-                               pool_reset_memqcache_buffer();
+                               pool_reset_memqcache_buffer(true);
 
                                pfree(oids);
                                ereport(DEBUG2,
@@ -3334,7 +3339,7 @@ void pool_handle_query_cache(POOL_CONNECTION_POOL *backend, char *query, Node *n
                                        pool_invalidate_query_cache(num_oids, oids, true, 0);
                                        pool_shmem_unlock();
                                        POOL_SETMASK(&oldmask);
-                                       pool_reset_memqcache_buffer();
+                                       pool_reset_memqcache_buffer(true);
                                }
                                else
                                {
@@ -3345,8 +3350,8 @@ void pool_handle_query_cache(POOL_CONNECTION_POOL *backend, char *query, Node *n
                                         * if DML/DDL modifies the TABLE which SELECT uses.
                                         */
                                        pool_check_and_discard_cache_buffer(num_oids, oids);
-                                       pool_reset_memqcache_buffer();
-                               } 
+                                       pool_reset_memqcache_buffer(false);
+                               }
                        }
                        else if (num_oids == 0)
                        {
@@ -3354,7 +3359,7 @@ void pool_handle_query_cache(POOL_CONNECTION_POOL *backend, char *query, Node *n
                                 * It is also necessary to clear cache buffers in case of
                                 * no oid queries (like BEGIN, CHECKPOINT, VACUUM, etc) too.
                                 */
-                               pool_reset_memqcache_buffer();
+                               pool_reset_memqcache_buffer(true);
                        }
                }
        }