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raw | patch | inline | side by side (parent: b60d581)
raw | patch | inline | side by side (parent: b60d581)
author | Sebastian Harl <sh@tokkee.org> | |
Tue, 6 Oct 2015 19:47:34 +0000 (21:47 +0200) | ||
committer | Sebastian Harl <sh@tokkee.org> | |
Tue, 6 Oct 2015 19:47:34 +0000 (21:47 +0200) |
Instead of letting the query implementation write JSON directly, let them emit
objects to a store-writer. This allows for more powerful and centralized
post-processing of the data and avoids code-duplication by moving all logic of
how to write out the data to the core. Also, this had a couple of nice side
effects and allowed for further simplication:
- The TIMESERIES command is now handled by the front-end (based on a FETCH of
the respective metric data); query plugin no longer have to implement this.
- All protocol specific information is now handled by the frontend; query
plugins no longer have to handle this (response-type).
- Further separation of the memory-store and generic store code.
objects to a store-writer. This allows for more powerful and centralized
post-processing of the data and avoids code-duplication by moving all logic of
how to write out the data to the core. Also, this had a couple of nice side
effects and allowed for further simplication:
- The TIMESERIES command is now handled by the front-end (based on a FETCH of
the respective metric data); query plugin no longer have to implement this.
- All protocol specific information is now handled by the frontend; query
plugins no longer have to handle this (response-type).
- Further separation of the memory-store and generic store code.
diff --git a/src/core/plugin.c b/src/core/plugin.c
index 897769926584b201fab1657ecd0885719486cce4..3611be4966b51d296557620e9ed77abda9d7ce48 100644 (file)
--- a/src/core/plugin.c
+++ b/src/core/plugin.c
} /* sdb_plugin_fetch_timeseries */
int
-sdb_plugin_query(sdb_ast_node_t *ast, sdb_strbuf_t *buf, sdb_strbuf_t *errbuf)
+sdb_plugin_query(sdb_ast_node_t *ast,
+ sdb_store_writer_t *w, sdb_object_t *wd, sdb_strbuf_t *errbuf)
{
size_t n = sdb_llist_len(reader_list);
reader_t *reader;
@@ -1449,8 +1450,7 @@ sdb_plugin_query(sdb_ast_node_t *ast, sdb_strbuf_t *buf, sdb_strbuf_t *errbuf)
if ((ast->type != SDB_AST_TYPE_FETCH)
&& (ast->type != SDB_AST_TYPE_LIST)
- && (ast->type != SDB_AST_TYPE_LOOKUP)
- && (ast->type != SDB_AST_TYPE_TIMESERIES)) {
+ && (ast->type != SDB_AST_TYPE_LOOKUP)) {
sdb_log(SDB_LOG_ERR, "core: Cannot execute query of type %s",
SDB_AST_TYPE_TO_STRING(ast));
sdb_strbuf_sprintf(errbuf, "Cannot execute query of type %s",
@@ -1472,7 +1472,8 @@ sdb_plugin_query(sdb_ast_node_t *ast, sdb_strbuf_t *buf, sdb_strbuf_t *errbuf)
q = reader->impl.prepare_query(ast, errbuf, reader->r_user_data);
if (q)
- status = reader->impl.execute_query(q, buf, errbuf, reader->r_user_data);
+ status = reader->impl.execute_query(q, w, SDB_OBJ(wd),
+ errbuf, reader->r_user_data);
else
status = -1;
diff --git a/src/core/store.c b/src/core/store.c
index dfa6ac9692499b45edd5be129ff59242375ebaed..fa72955886bfa04778daa110bc02515b909919b1 100644 (file)
--- a/src/core/store.c
+++ b/src/core/store.c
static int
execute_query(sdb_object_t *q,
- sdb_strbuf_t *buf, sdb_strbuf_t *errbuf,
+ sdb_store_writer_t *w, sdb_object_t *wd, sdb_strbuf_t *errbuf,
sdb_object_t *user_data)
{
return sdb_store_query_execute(SDB_STORE(user_data),
- QUERY(q), buf, errbuf);
+ QUERY(q), w, wd, errbuf);
} /* execute_query */
sdb_store_reader_t sdb_store_reader = {
return 0;
} /* sdb_store_get_attr */
-/* TODO: sdb_store_fetch_timeseries should move into the plugin module */
-
-int
-sdb_store_fetch_timeseries(sdb_store_t *store,
- const char *hostname, const char *metric,
- sdb_timeseries_opts_t *opts, sdb_strbuf_t *buf)
-{
- sdb_avltree_t *metrics;
- host_t *host;
- sdb_metric_t *m;
-
- sdb_timeseries_t *ts;
-
- int status = 0;
-
- if ((! store) || (! hostname) || (! metric) || (! opts) || (! buf))
- return -1;
-
- pthread_rwlock_rdlock(&store->host_lock);
- host = HOST(sdb_avltree_lookup(store->hosts, hostname));
- metrics = get_host_children(host, SDB_METRIC);
- sdb_object_deref(SDB_OBJ(host));
- if (! metrics) {
- sdb_log(SDB_LOG_ERR, "store: Failed to fetch time-series '%s/%s' "
- "- host '%s' not found", hostname, metric, hostname);
- pthread_rwlock_unlock(&store->host_lock);
- return -1;
- }
-
- m = METRIC(sdb_avltree_lookup(metrics, metric));
- if (! m) {
- sdb_log(SDB_LOG_ERR, "store: Failed to fetch time-series '%s/%s' "
- "- metric '%s' not found", hostname, metric, metric);
- pthread_rwlock_unlock(&store->host_lock);
- return -1;
- }
-
- if ((! m->store.type) || (! m->store.id)) {
- sdb_log(SDB_LOG_ERR, "store: Failed to fetch time-series '%s/%s' "
- "- no data-store configured for the stored metric",
- hostname, metric);
- sdb_object_deref(SDB_OBJ(m));
- pthread_rwlock_unlock(&store->host_lock);
- return -1;
- }
-
- {
- char type[strlen(m->store.type) + 1];
- char id[strlen(m->store.id) + 1];
-
- strncpy(type, m->store.type, sizeof(type));
- strncpy(id, m->store.id, sizeof(id));
- pthread_rwlock_unlock(&store->host_lock);
-
- ts = sdb_plugin_fetch_timeseries(type, id, opts);
- if (! ts) {
- sdb_log(SDB_LOG_ERR, "store: Failed to fetch time-series '%s/%s' "
- "- %s fetcher callback returned no data for '%s'",
- hostname, metric, type, id);
- status = -1;
- }
- }
-
- sdb_timeseries_tojson(ts, buf);
- sdb_object_deref(SDB_OBJ(m));
- sdb_timeseries_destroy(ts);
- return status;
-} /* sdb_store_fetch_timeseries */
-
int
sdb_store_scan(sdb_store_t *store, int type,
sdb_store_matcher_t *m, sdb_store_matcher_t *filter,
diff --git a/src/core/store_exec.c b/src/core/store_exec.c
index 6cf3a820bd3a013e770d3f172de2a1728649ff19..d4e308806bac8ece40c9a12a20885df768c2dffe 100644 (file)
--- a/src/core/store_exec.c
+++ b/src/core/store_exec.c
*/
static int
-exec_fetch(sdb_store_t *store, sdb_strbuf_t *buf, sdb_strbuf_t *errbuf,
+exec_fetch(sdb_store_t *store,
+ sdb_store_writer_t *w, sdb_object_t *wd, sdb_strbuf_t *errbuf,
int type, const char *hostname, const char *name,
sdb_store_matcher_t *filter)
{
- uint32_t res_type = htonl(SDB_CONNECTION_FETCH);
-
sdb_store_obj_t *host;
sdb_store_obj_t *obj;
- sdb_store_json_formatter_t *f;
int status = 0;
if ((! name) || ((type == SDB_HOST) && hostname)
}
host = NULL;
- f = sdb_store_json_formatter(buf, type, /* flags = */ 0);
- if (! f) {
- char err[1024];
- sdb_log(SDB_LOG_ERR, "frontend: Failed to create "
- "JSON formatter to handle FETCH command: %s",
- sdb_strerror(errno, err, sizeof(err)));
-
- sdb_strbuf_sprintf(errbuf, "Out of memory");
- sdb_object_deref(SDB_OBJ(obj));
- return -1;
- }
-
- sdb_strbuf_memcpy(buf, &res_type, sizeof(uint32_t));
if (type != SDB_HOST)
- status = sdb_store_emit(obj->parent,
- &sdb_store_json_writer, SDB_OBJ(f));
- if (status || sdb_store_emit_full(obj, filter,
- &sdb_store_json_writer, SDB_OBJ(f))) {
+ status = sdb_store_emit(obj->parent, w, wd);
+ if (status || sdb_store_emit_full(obj, filter, w, wd)) {
sdb_log(SDB_LOG_ERR, "frontend: Failed to serialize "
"%s %s.%s to JSON", SDB_STORE_TYPE_TO_NAME(type),
hostname, name);
sdb_strbuf_sprintf(errbuf, "Out of memory");
- sdb_object_deref(SDB_OBJ(f));
sdb_object_deref(SDB_OBJ(obj));
return -1;
}
sdb_object_deref(SDB_OBJ(obj));
- sdb_store_json_finish(f);
- sdb_object_deref(SDB_OBJ(f));
-
return SDB_CONNECTION_DATA;
} /* exec_fetch */
static int
-exec_list(sdb_store_t *store, sdb_strbuf_t *buf, sdb_strbuf_t *errbuf,
+exec_list(sdb_store_t *store,
+ sdb_store_writer_t *w, sdb_object_t *wd, sdb_strbuf_t *errbuf,
int type, sdb_store_matcher_t *filter)
{
- uint32_t res_type = htonl(SDB_CONNECTION_LIST);
- iter_t iter = { NULL, &sdb_store_json_writer, NULL };
- sdb_store_json_formatter_t *f;
+ iter_t iter = { NULL, w, wd };
- f = sdb_store_json_formatter(buf, type, SDB_WANT_ARRAY);
- if (! f) {
- char err[1024];
- sdb_log(SDB_LOG_ERR, "frontend: Failed to create "
- "JSON formatter to handle LIST command: %s",
- sdb_strerror(errno, err, sizeof(err)));
-
- sdb_strbuf_sprintf(errbuf, "Out of memory");
- return -1;
- }
-
- iter.wd = SDB_OBJ(f);
- sdb_strbuf_memcpy(buf, &res_type, sizeof(uint32_t));
if (sdb_store_scan(store, type, /* m = */ NULL, filter, list_tojson, &iter)) {
sdb_log(SDB_LOG_ERR, "frontend: Failed to serialize "
"store to JSON");
sdb_strbuf_sprintf(errbuf, "Out of memory");
- sdb_object_deref(SDB_OBJ(f));
return -1;
}
- sdb_store_json_finish(f);
- sdb_object_deref(SDB_OBJ(f));
-
return SDB_CONNECTION_DATA;
} /* exec_list */
static int
-exec_lookup(sdb_store_t *store, sdb_strbuf_t *buf, sdb_strbuf_t *errbuf,
+exec_lookup(sdb_store_t *store,
+ sdb_store_writer_t *w, sdb_object_t *wd, sdb_strbuf_t *errbuf,
int type, sdb_store_matcher_t *m, sdb_store_matcher_t *filter)
{
- uint32_t res_type = htonl(SDB_CONNECTION_LOOKUP);
- iter_t iter = { NULL, &sdb_store_json_writer, NULL };
- sdb_store_json_formatter_t *f;
-
- f = sdb_store_json_formatter(buf, type, SDB_WANT_ARRAY);
- if (! f) {
- char err[1024];
- sdb_log(SDB_LOG_ERR, "frontend: Failed to create "
- "JSON formatter to handle LOOKUP command: %s",
- sdb_strerror(errno, err, sizeof(err)));
+ iter_t iter = { NULL, w, wd };
- sdb_strbuf_sprintf(errbuf, "Out of memory");
- return -1;
- }
-
- iter.wd = SDB_OBJ(f);
- sdb_strbuf_memcpy(buf, &res_type, sizeof(uint32_t));
if (sdb_store_scan(store, type, m, filter, lookup_tojson, &iter)) {
sdb_log(SDB_LOG_ERR, "frontend: Failed to lookup %ss",
SDB_STORE_TYPE_TO_NAME(type));
sdb_strbuf_sprintf(errbuf, "Failed to lookup %ss",
SDB_STORE_TYPE_TO_NAME(type));
- sdb_object_deref(SDB_OBJ(f));
return -1;
}
- sdb_store_json_finish(f);
- sdb_object_deref(SDB_OBJ(f));
-
return SDB_CONNECTION_DATA;
} /* exec_lookup */
-static int
-exec_timeseries(sdb_store_t *store, sdb_strbuf_t *buf, sdb_strbuf_t *errbuf,
- const char *hostname, const char *metric,
- sdb_timeseries_opts_t *opts)
-{
- uint32_t res_type = htonl(SDB_CONNECTION_TIMESERIES);
-
- sdb_strbuf_memcpy(buf, &res_type, sizeof(uint32_t));
- if (sdb_store_fetch_timeseries(store, hostname, metric, opts, buf)) {
- sdb_log(SDB_LOG_ERR, "frontend: Failed to fetch time-series");
- sdb_strbuf_sprintf(errbuf, "Failed to fetch time-series");
- return -1;
- }
-
- return SDB_CONNECTION_DATA;
-} /* exec_timeseries */
-
/*
* public API
*/
int
sdb_store_query_execute(sdb_store_t *store, sdb_store_query_t *q,
- sdb_strbuf_t *buf, sdb_strbuf_t *errbuf)
+ sdb_store_writer_t *w, sdb_object_t *wd, sdb_strbuf_t *errbuf)
{
- sdb_timeseries_opts_t ts_opts;
sdb_ast_node_t *ast;
if (! q)
ast = q->ast;
switch (ast->type) {
case SDB_AST_TYPE_FETCH:
- return exec_fetch(store, buf, errbuf, SDB_AST_FETCH(ast)->obj_type,
+ return exec_fetch(store, w, wd, errbuf, SDB_AST_FETCH(ast)->obj_type,
SDB_AST_FETCH(ast)->hostname, SDB_AST_FETCH(ast)->name,
q->filter);
case SDB_AST_TYPE_LIST:
- return exec_list(store, buf, errbuf, SDB_AST_LIST(ast)->obj_type,
+ return exec_list(store, w, wd, errbuf, SDB_AST_LIST(ast)->obj_type,
q->filter);
case SDB_AST_TYPE_LOOKUP:
- return exec_lookup(store, buf, errbuf, SDB_AST_LOOKUP(ast)->obj_type,
+ return exec_lookup(store, w, wd, errbuf, SDB_AST_LOOKUP(ast)->obj_type,
q->matcher, q->filter);
- case SDB_AST_TYPE_TIMESERIES:
- ts_opts.start = SDB_AST_TIMESERIES(ast)->start;
- ts_opts.end = SDB_AST_TIMESERIES(ast)->end;
- return exec_timeseries(store, buf, errbuf,
- SDB_AST_TIMESERIES(ast)->hostname,
- SDB_AST_TIMESERIES(ast)->metric, &ts_opts);
-
default:
sdb_log(SDB_LOG_ERR, "store: Invalid query of type %s",
SDB_AST_TYPE_TO_STRING(ast));
diff --git a/src/frontend/query.c b/src/frontend/query.c
index 56cd4ec86638ef537d8bdc09fabc15e4b90ed0b0..9a157fb892d10888e35a74c84d77d5a18e635599 100644 (file)
--- a/src/frontend/query.c
+++ b/src/frontend/query.c
#include <ctype.h>
#include <string.h>
+/*
+ * metric fetcher:
+ * Implements the callbacks necessary to read a metric object.
+ * TODO: FETCH should allow to ignore child elements (attributes); then, we'd
+ * only need store_host/store_metric.
+ */
+
+typedef struct {
+ char *type;
+ char *id;
+} metric_store_t;
+
+static int
+metric_fetcher_host(sdb_store_host_t __attribute__((unused)) *host,
+ sdb_object_t __attribute__((unused)) *user_data)
+{
+ return 0;
+} /* metric_fetcher_host */
+
+static int
+metric_fetcher_metric(sdb_store_metric_t *metric, sdb_object_t *user_data)
+{
+ metric_store_t *st = SDB_OBJ_WRAPPER(user_data)->data;
+
+ if ((! metric->store.type) || (! metric->store.id))
+ return 0;
+
+ st->type = strdup(metric->store.type);
+ st->id = strdup(metric->store.id);
+ if ((! st->type) || (! st->id))
+ return -1;
+ return 0;
+} /* metric_fetcher_metric */
+
+static int
+metric_fetcher_attr(sdb_store_attribute_t __attribute__((unused)) *attr,
+ sdb_object_t __attribute__((unused)) *user_data)
+{
+ return 0;
+} /* metric_fetcher_attr */
+
+static sdb_store_writer_t metric_fetcher = {
+ metric_fetcher_host, NULL, metric_fetcher_metric, metric_fetcher_attr,
+};
+
/*
* private helper functions
*/
return s ? strlen(s) : 0;
} /* sstrlen */
+static int
+exec_query(sdb_ast_node_t *ast, sdb_strbuf_t *buf, sdb_strbuf_t *errbuf)
+{
+ sdb_store_json_formatter_t *f;
+ int type = 0, flags = 0;
+ uint32_t res_type = 0;
+ int status;
+
+ switch (ast->type) {
+ case SDB_AST_TYPE_FETCH:
+ type = SDB_AST_FETCH(ast)->obj_type;
+ res_type = htonl(SDB_CONNECTION_FETCH);
+ break;
+ case SDB_AST_TYPE_LIST:
+ type = SDB_AST_LIST(ast)->obj_type;
+ flags = SDB_WANT_ARRAY;
+ res_type = htonl(SDB_CONNECTION_LIST);
+ break;
+ case SDB_AST_TYPE_LOOKUP:
+ type = SDB_AST_LOOKUP(ast)->obj_type;
+ flags = SDB_WANT_ARRAY;
+ res_type = htonl(SDB_CONNECTION_LOOKUP);
+ break;
+ default:
+ sdb_strbuf_sprintf(errbuf, "invalid command %s (%#x)",
+ SDB_AST_TYPE_TO_STRING(ast), ast->type);
+ return -1;
+ }
+
+ f = sdb_store_json_formatter(buf, type, flags);
+ sdb_strbuf_memcpy(buf, &res_type, sizeof(res_type));
+ status = sdb_plugin_query(ast, &sdb_store_json_writer, SDB_OBJ(f), errbuf);
+ if (status < 0)
+ sdb_strbuf_clear(buf);
+ sdb_store_json_finish(f);
+ sdb_object_deref(SDB_OBJ(f));
+ return status;
+} /* exec_query */
+
static int
exec_store(sdb_ast_store_t *st, sdb_strbuf_t *buf, sdb_strbuf_t *errbuf)
{
} /* exec_store */
static int
-exec_query(sdb_conn_t *conn, sdb_ast_node_t *ast)
+exec_timeseries(sdb_ast_timeseries_t *ts, sdb_strbuf_t *buf, sdb_strbuf_t *errbuf)
+{
+ metric_store_t st = { NULL, NULL };
+ sdb_object_wrapper_t obj = SDB_OBJECT_WRAPPER_STATIC(&st);
+ sdb_ast_fetch_t fetch = SDB_AST_FETCH_INIT;
+ sdb_timeseries_opts_t opts = { 0, 0 };
+ sdb_timeseries_t *series = NULL;
+ int status;
+
+ if ((! ts) || (! ts->hostname) || (! ts->metric))
+ return -1;
+
+ fetch.obj_type = SDB_METRIC;
+ fetch.hostname = strdup(ts->hostname);
+ fetch.name = strdup(ts->metric);
+ opts.start = ts->start;
+ opts.end = ts->end;
+
+ status = sdb_plugin_query(SDB_AST_NODE(&fetch),
+ &metric_fetcher, SDB_OBJ(&obj), errbuf);
+ if ((status < 0) || (! st.type) || (! st.id)) {
+ sdb_log(SDB_LOG_ERR, "frontend: Failed to fetch time-series '%s/%s' "
+ "- no data-store configured for the stored metric",
+ ts->hostname, ts->metric);
+ status = -1;
+ }
+ if (status >= 0) {
+ series = sdb_plugin_fetch_timeseries(st.type, st.id, &opts);
+ if (! series) {
+ sdb_log(SDB_LOG_ERR, "frontend: Failed to fetch time-series '%s/%s' "
+ "- %s fetcher callback returned no data for '%s'",
+ ts->hostname, ts->metric, st.type, st.id);
+ status = -1;
+ }
+ }
+
+ if (status >= 0) {
+ sdb_timeseries_tojson(series, buf);
+ sdb_timeseries_destroy(series);
+ }
+
+ free(fetch.hostname);
+ free(fetch.name);
+ if (st.type)
+ free(st.type);
+ if (st.id)
+ free(st.id);
+ return status;
+} /* exec_timeseries */
+
+static int
+exec_cmd(sdb_conn_t *conn, sdb_ast_node_t *ast)
{
sdb_strbuf_t *buf;
int status;
sdb_strbuf_sprintf(conn->errbuf, "Out of memory");
return -1;
}
+
if (ast->type == SDB_AST_TYPE_STORE)
status = exec_store(SDB_AST_STORE(ast), buf, conn->errbuf);
+ else if (ast->type == SDB_AST_TYPE_TIMESERIES)
+ status = exec_timeseries(SDB_AST_TIMESERIES(ast), buf, conn->errbuf);
else
- status = sdb_plugin_query(ast, buf, conn->errbuf);
+ status = exec_query(ast, buf, conn->errbuf);
+
if (status < 0) {
char query[conn->cmd_len + 1];
strncpy(query, sdb_strbuf_string(conn->buf), conn->cmd_len);
sdb_strbuf_destroy(buf);
return status < 0 ? status : 0;
-} /* exec_query */
+} /* exec_cmd */
/*
* public API
}
if (ast) {
- status = exec_query(conn, ast);
+ status = exec_cmd(conn, ast);
sdb_object_deref(SDB_OBJ(ast));
}
sdb_llist_destroy(parsetree);
hostname[0] ? strdup(hostname) : NULL,
name[0] ? strdup(name) : NULL,
/* filter = */ NULL);
- status = exec_query(conn, ast);
+ status = exec_cmd(conn, ast);
sdb_object_deref(SDB_OBJ(ast));
return status;
} /* sdb_conn_fetch */
}
ast = sdb_ast_list_create((int)type, /* filter = */ NULL);
- status = exec_query(conn, ast);
+ status = exec_cmd(conn, ast);
sdb_object_deref(SDB_OBJ(ast));
return status;
} /* sdb_conn_list */
}
ast = sdb_ast_lookup_create((int)type, m, /* filter = */ NULL);
- status = exec_query(conn, ast);
+ status = exec_cmd(conn, ast);
if (! ast)
sdb_object_deref(SDB_OBJ(m));
sdb_object_deref(SDB_OBJ(ast));
status = sdb_parser_analyze(ast, conn->errbuf);
if (! status)
- status = exec_query(conn, ast);
+ status = exec_cmd(conn, ast);
sdb_object_deref(SDB_OBJ(ast));
return status;
} /* sdb_conn_store */
index 6b5a9f46268b928c4284e5910afe3117f964d25c..6c4a2e16cfdf674c2884f560ac158ef7836733d3 100644 (file)
* - a negative value else
*/
int
-sdb_plugin_query(sdb_ast_node_t *ast, sdb_strbuf_t *buf, sdb_strbuf_t *errbuf);
+sdb_plugin_query(sdb_ast_node_t *ast,
+ sdb_store_writer_t *w, sdb_object_t *wd, sdb_strbuf_t *errbuf);
/*
* sdb_plugin_store_host, sdb_plugin_store_service, sdb_plugin_store_metric,
index f42d217ebe5dba73541d79a0de74a94d8f2081b7..0cee91362998d55c4f329c031572d5096e68400c 100644 (file)
--- a/src/include/core/store.h
+++ b/src/include/core/store.h
* execute_query:
* Execute a previously prepared query. The callback may expect that only
* queries prepared by its respective prepare callback will be passed to
- * this function.
- *
- * TODO: Instead of letting the executor write directly to a string buffer
- * (which cannot easily be merged with other results), let it hand
- * all objects to a store-writer.
+ * this function. The query result will be passed back via the specified
+ * store writer.
*/
int (*execute_query)(sdb_object_t *q,
- sdb_strbuf_t *buf, sdb_strbuf_t *errbuf,
- sdb_object_t *user_data);
+ sdb_store_writer_t *w, sdb_object_t *wd,
+ sdb_strbuf_t *errbuf, sdb_object_t *user_data);
} sdb_store_reader_t;
/*
*/
int
sdb_store_query_execute(sdb_store_t *store, sdb_store_query_t *m,
- sdb_strbuf_t *buf, sdb_strbuf_t *errbuf);
+ sdb_store_writer_t *w, sdb_object_t *wd, sdb_strbuf_t *errbuf);
/*
* sdb_store_expr_create: