[t:1869], checkin fix with added variable to allow disabling of feature

git-svn-id: file:///svn/mysql/tokudb-engine/src@14521 c7de825b-a66e-492c-adef-691d508d4ae1

storage/tokudb/ha_tokudb.cc

@@ -1379,6 +1379,13 @@ int ha_tokudb::initialize_share(
         init_auto_increment();
     }
 
+    if (may_table_be_empty()) {
+        share->try_table_lock = true;
+    }
+    else {
+        share->try_table_lock = false;
+    }
+
     error = 0;
 exit:
     my_free(newname, MYF(MY_ALLOW_ZERO_PTR));
@@ -2547,6 +2554,47 @@ bool ha_tokudb::check_if_incompatible_data(HA_CREATE_INFO * info, uint table_cha
 //                     "insert into foo select * from bar), then rows 
 //                     will be 0
 //
+//
+// This function returns true if the table MAY be empty.
+// It is NOT meant to be a 100% check for emptiness.
+// This is used for a bulk load optimization.
+//
+bool ha_tokudb::may_table_be_empty() {
+    int error;
+    bool ret_val = false;
+    DBC* tmp_cursor = NULL;
+    DB_TXN* txn = NULL;
+
+    error = db_env->txn_begin(db_env, 0, &txn, 0);
+    if (error) {
+        goto cleanup;
+    }
+
+    error = share->file->cursor(share->file, txn, &tmp_cursor, 0);
+    if (error) {
+        goto cleanup;
+    }
+    error = tmp_cursor->c_getf_next(tmp_cursor, 0, smart_dbt_do_nothing, NULL);
+    if (error == DB_NOTFOUND) {
+        ret_val = true;
+    }
+    else {
+        ret_val = false;
+    }
+    error = 0;
+cleanup:
+    if (tmp_cursor) {
+        tmp_cursor->c_close(tmp_cursor);
+        tmp_cursor = NULL;
+    }
+    if (txn) {
+        int r = txn->commit(txn, 0);
+        assert(r == 0);
+        txn = NULL;
+    }
+    return ret_val;
+}
+
 void ha_tokudb::start_bulk_insert(ha_rows rows) {
     //
     // make sure delay_updating_ai_metadata is true, iff the auto inc column
@@ -2554,6 +2602,14 @@ void ha_tokudb::start_bulk_insert(ha_rows rows) {
     //
     delay_updating_ai_metadata = share->ai_first_col;
     ai_metadata_update_required = false;
+    if (share->try_table_lock) {
+        if (may_table_be_empty() && tokudb_prelock_empty) {
+            acquire_table_lock(transaction, lock_write);
+        }
+        pthread_mutex_lock(&share->mutex);
+        share->try_table_lock = false;
+        pthread_mutex_unlock(&share->mutex);
+    }
 }
 
 //

storage/tokudb/ha_tokudb.h

@@ -70,6 +70,13 @@ typedef struct st_tokudb_share {
     MULTI_COL_PACK_INFO mcp_info[MAX_KEY+1];
     COL_PACK_INFO* cp_info[MAX_KEY+1];
     u_int32_t num_offset_bytes; //number of bytes needed to encode the offset
+    // 
+    // we want the following optimization for bulk loads, if the table is empty, 
+    // attempt to grab a table lock. emptiness check can be expensive, 
+    // so we try it once for a table. After that, we keep this variable around 
+    // to tell us to not try it again. 
+    // 
+    bool try_table_lock; 
 } TOKUDB_SHARE;
 
 #define HA_TOKU_VERSION 2
@@ -277,6 +284,7 @@ class ha_tokudb : public handler {
     void set_query_columns(uint keynr);
     int prelock_range ( const key_range *start_key, const key_range *end_key);
     int create_txn(THD* thd, tokudb_trx_data* trx);
+    bool may_table_be_empty();
 
 
  

storage/tokudb/hatoku_hton.cc

@@ -107,6 +107,7 @@ static ulong tokudb_max_lock;
 static const char tokudb_hton_name[] = "TokuDB";
 static const int tokudb_hton_name_length = sizeof(tokudb_hton_name) - 1;
 static u_int32_t tokudb_checkpointing_period;
+my_bool tokudb_prelock_empty;
 #ifdef TOKUDB_VERSION
  char *tokudb_version = TOKUDB_VERSION;
 #else
@@ -766,6 +767,7 @@ static MYSQL_SYSVAR_STR(version, tokudb_version, PLUGIN_VAR_READONLY, "TokuDB Ve
 static MYSQL_SYSVAR_UINT(init_flags, tokudb_init_flags, PLUGIN_VAR_READONLY, "Sets TokuDB DB_ENV->open flags", NULL, NULL, tokudb_init_flags, 0, ~0, 0);
 
 static MYSQL_SYSVAR_UINT(checkpointing_period, tokudb_checkpointing_period, 0, "TokuDB Checkpointing period", NULL, NULL, 60, 0, ~0L, 0);
+static MYSQL_SYSVAR_BOOL(prelock_empty, tokudb_prelock_empty, 0, "Tokudb Shared Data", NULL, NULL, TRUE);
 #if 0
 
 static MYSQL_SYSVAR_ULONG(cache_parts, tokudb_cache_parts, PLUGIN_VAR_READONLY, "Sets TokuDB set_cache_parts", NULL, NULL, 0, 0, ~0L, 0);
@@ -805,6 +807,7 @@ static struct st_mysql_sys_var *tokudb_system_variables[] = {
     MYSQL_SYSVAR(version),
     MYSQL_SYSVAR(init_flags),
     MYSQL_SYSVAR(checkpointing_period),
+    MYSQL_SYSVAR(prelock_empty),
 #if 0
     MYSQL_SYSVAR(cache_parts),
     MYSQL_SYSVAR(env_flags),

storage/tokudb/hatoku_hton.h

@@ -16,9 +16,6 @@ extern DB *metadata_db;
 extern HASH tokudb_open_tables;
 extern pthread_mutex_t tokudb_mutex;
 extern pthread_mutex_t tokudb_meta_mutex;
-
-
-
-
+extern my_bool tokudb_prelock_empty;
 
 #endif //#ifdef _HATOKU_HTON