X-Git-Url: https://git.tokkee.org/?p=sysdb.git;a=blobdiff_plain;f=src%2Finclude%2Fcore%2Fstore.h;h=f0fc0c7d779cf4504eb67f316c6846c8f7e99303;hp=c25c278a327f5904ec8252cdee65ac9dc3da15d8;hb=1f99d1a0d8a7e923dede7c938340c26061b8398b;hpb=914549be3bfffdd3ad4b2599ed1e771d857512da

diff --git a/src/include/core/store.h b/src/include/core/store.h
index c25c278..f0fc0c7 100644
--- a/src/include/core/store.h
+++ b/src/include/core/store.h
@@ -1,6 +1,6 @@
 /*
  * SysDB - src/include/core/store.h
- * Copyright (C) 2012 Sebastian 'tokkee' Harl <sh@tokkee.org>
+ * Copyright (C) 2012-2015 Sebastian 'tokkee' Harl <sh@tokkee.org>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -33,6 +33,7 @@
 #include "core/data.h"
 #include "core/time.h"
 #include "core/timeseries.h"
+#include "parser/ast.h"
 #include "utils/strbuf.h"
 
 #include <stdio.h>
@@ -48,70 +49,39 @@ enum {
 	SDB_HOST = 1,
 	SDB_SERVICE,
 	SDB_METRIC,
-	SDB_ATTRIBUTE,
+
+	SDB_ATTRIBUTE = 1 << 4,
+
+	/*
+	 * Queryable fields of a stored object.
+	 */
+	SDB_FIELD_NAME = 1 << 8, /* type: string */
+	SDB_FIELD_LAST_UPDATE,   /* type: datetime */
+	SDB_FIELD_AGE,           /* type: datetime */
+	SDB_FIELD_INTERVAL,      /* type: datetime */
+	SDB_FIELD_BACKEND,       /* type: array of strings */
+	SDB_FIELD_VALUE,         /* attributes only;  type: type of the value */
+	SDB_FIELD_TIMESERIES,    /* metrics only;  type: boolean */
 };
 #define SDB_STORE_TYPE_TO_NAME(t) \
 	(((t) == SDB_HOST) ? "host" \
 		: ((t) == SDB_SERVICE) ? "service" \
 		: ((t) == SDB_METRIC) ? "metric" \
-		: ((t) == SDB_ATTRIBUTE) ? "attribute" : "unknown")
-
-/*
- * sdb_store_obj_t represents the super-class of any object stored in the
- * database. It inherits from sdb_object_t and may safely be cast to a generic
- * object to access its name.
- */
-struct sdb_store_obj;
-typedef struct sdb_store_obj sdb_store_obj_t;
-
-/*
- * Expressions represent arithmetic expressions based on stored objects and
- * their various attributes.
- *
- * An expression object inherits from sdb_object_t and, thus, may safely be
- * cast to a generic object.
- */
-struct sdb_store_expr;
-typedef struct sdb_store_expr sdb_store_expr_t;
-#define SDB_STORE_EXPR(obj) ((sdb_store_expr_t *)(obj))
-
-/*
- * Store matchers may be used to lookup hosts from the store based on their
- * various attributes. Service and attribute matchers are applied to a host's
- * services and attributes and evaluate to true if *any* service or attribute
- * matches.
- *
- * A store matcher object inherits from sdb_object_t and, thus, may safely be
- * cast to a generic object.
- */
-struct sdb_store_matcher;
-typedef struct sdb_store_matcher sdb_store_matcher_t;
-#define SDB_STORE_MATCHER(obj) ((sdb_store_matcher_t *)(obj))
-
-/*
- * A JSON formatter converts stored objects into the JSON format.
- * See http://www.ietf.org/rfc/rfc4627.txt
- */
-struct sdb_store_json_formatter;
-typedef struct sdb_store_json_formatter sdb_store_json_formatter_t;
-
-/*
- * Queryable fields of a stored object.
- */
-enum {
-	SDB_FIELD_NAME = 1,    /* string */
-	SDB_FIELD_LAST_UPDATE, /* datetime */
-	SDB_FIELD_AGE,         /* datetime */
-	SDB_FIELD_INTERVAL,    /* datetime */
-	SDB_FIELD_BACKEND,     /* string */
-};
+		: ((t) == SDB_ATTRIBUTE) ? "attribute" \
+		: ((t) == (SDB_ATTRIBUTE | SDB_HOST)) ? "host attribute" \
+		: ((t) == (SDB_ATTRIBUTE | SDB_SERVICE)) ? "service attribute" \
+		: ((t) == (SDB_ATTRIBUTE | SDB_METRIC)) ? "metric attribute" \
+		: "unknown")
 
 #define SDB_FIELD_TO_NAME(f) \
 	(((f) == SDB_FIELD_NAME) ? "name" \
 		: ((f) == SDB_FIELD_LAST_UPDATE) ? "last-update" \
 		: ((f) == SDB_FIELD_AGE) ? "age" \
 		: ((f) == SDB_FIELD_INTERVAL) ? "interval" \
-		: ((f) == SDB_FIELD_BACKEND) ? "backend" : "unknown")
+		: ((f) == SDB_FIELD_BACKEND) ? "backend" \
+		: ((f) == SDB_FIELD_VALUE) ? "value" \
+		: ((f) == SDB_FIELD_TIMESERIES) ? "timeseries" \
+		: "unknown")
 
 #define SDB_FIELD_TYPE(f) \
 	(((f) == SDB_FIELD_NAME) ? SDB_TYPE_STRING \
@@ -119,508 +89,172 @@ enum {
 		: ((f) == SDB_FIELD_AGE) ? SDB_TYPE_DATETIME \
 		: ((f) == SDB_FIELD_INTERVAL) ? SDB_TYPE_DATETIME \
 		: ((f) == SDB_FIELD_BACKEND) ? (SDB_TYPE_ARRAY | SDB_TYPE_STRING) \
+		: ((f) == SDB_FIELD_VALUE) ? -1 /* unknown */ \
+		: ((f) == SDB_FIELD_TIMESERIES) ? SDB_TYPE_BOOLEAN \
 		: -1)
 
 /*
- * sdb_store_clear:
- * Clear the entire store and remove all stored objects.
- */
-void
-sdb_store_clear(void);
-
-/*
- * sdb_store_host:
- * Add/update a host in the store. If the host, identified by its
- * canonicalized name, already exists, it will be updated according to the
- * specified name and timestamp. Else, a new entry will be created in the
- * store. Any memory required for storing the entry will be allocated an
- * managed by the store itself.
- *
- * Returns:
- *  - 0 on success
- *  - a positive value if the new entry is older than the currently stored
- *    entry (in this case, no update will happen)
- *  - a negative value on error
- */
-int
-sdb_store_host(const char *name, sdb_time_t last_update);
-
-/*
- * sdb_store_has_host:
- * sdb_store_get_host:
- * Query the store for a host by its (canonicalized) name.
- *
- * sdb_store_get_host increments the ref count of the host object. The caller
- * needs to deref it when no longer using it.
+ * sdb_store_host_t represents the meta-data of a stored host object.
  */
-_Bool
-sdb_store_has_host(const char *name);
-
-sdb_store_obj_t *
-sdb_store_get_host(const char *name);
+typedef struct {
+	const char *name;
 
-/*
- * sdb_store_attribute:
- * Add/update a host's attribute in the store. If the attribute, identified by
- * its key, already exists for the specified host, it will be updated to the
- * specified values. If the referenced host does not exist, an error will be
- * reported. Else, a new entry will be created in the store. Any memory
- * required for storing the entry will be allocated and managed by the store
- * itself.
- *
- * Returns:
- *  - 0 on success
- *  - a positive value if the new entry is older than the currently stored
- *    entry (in this case, no update will happen)
- *  - a negative value on error
- */
-int
-sdb_store_attribute(const char *hostname,
-		const char *key, const sdb_data_t *value,
-		sdb_time_t last_update);
+	sdb_time_t last_update;
+	sdb_time_t interval;
+	const char * const *backends;
+	size_t backends_num;
+} sdb_store_host_t;
+#define SDB_STORE_HOST_INIT { NULL, 0, 0, NULL, 0 }
 
 /*
- * sdb_store_service:
- * Add/update a service in the store. If the service, identified by its name,
- * already exists for the specified host, it will be updated according to the
- * specified 'service' object. If the referenced host does not exist, an error
- * will be reported. Else, a new entry will be created in the store. Any
- * memory required for storing the entry will be allocated an managed by the
- * store itself.
- *
- * Returns:
- *  - 0 on success
- *  - a positive value if the new entry is older than the currently stored
- *    entry (in this case, no update will happen)
- *  - a negative value on error
+ * sdb_store_service_t represents the meta-data of a stored service object.
  */
-int
-sdb_store_service(const char *hostname, const char *name,
-		sdb_time_t last_update);
+typedef struct {
+	const char *hostname;
+	const char *name;
 
-/*
- * sdb_store_service_attr:
- * Add/update a service's attribute in the store. If the attribute, identified
- * by its key, already exists for the specified service, it will be updated to
- * the specified value. If the references service (for the specified host)
- * does not exist, an error will be reported. Any memory required for storing
- * the entry will be allocated and managed by the store itself.
- *
- * Returns:
- *  - 0 on success
- *  - a positive value if the new entry is older than the currently stored
- *    entry (in this case, no update will happen)
- *  - a negative value on error
- */
-int
-sdb_store_service_attr(const char *hostname, const char *service,
-		const char *key, const sdb_data_t *value, sdb_time_t last_update);
+	sdb_time_t last_update;
+	sdb_time_t interval;
+	const char * const *backends;
+	size_t backends_num;
+} sdb_store_service_t;
+#define SDB_STORE_SERVICE_INIT { NULL, NULL, 0, 0, NULL, 0 }
 
 /*
- * A metric store describes how to access a metric's data.
+ * sdb_metric_store_t specifies how to access a metric's data.
  */
 typedef struct {
 	const char *type;
 	const char *id;
+	const sdb_timeseries_info_t *info;
+	sdb_time_t last_update;
 } sdb_metric_store_t;
 
 /*
- * sdb_store_metric:
- * Add/update a metric in the store. If the metric, identified by its name,
- * already exists for the specified host, it will be updated according to the
- * specified 'metric' object. If the referenced host does not exist, an error
- * will be reported. Else, a new entry will be created in the store. Any
- * memory required for storing the entry will be allocated an managed by the
- * store itself.
- *
- * If specified, the metric store describes where to access the metric's data.
- *
- * Returns:
- *  - 0 on success
- *  - a positive value if the new entry is older than the currently stored
- *    entry (in this case, no update will happen)
- *  - a negative value on error
- */
-int
-sdb_store_metric(const char *hostname, const char *name,
-		sdb_metric_store_t *store, sdb_time_t last_update);
-
-/*
- * sdb_store_metric_attr:
- * Add/update a metric's attribute in the store. If the attribute, identified
- * by its key, already exists for the specified metric, it will be updated to
- * the specified value. If the references metric (for the specified host)
- * does not exist, an error will be reported. Any memory required for storing
- * the entry will be allocated and managed by the store itself.
- *
- * Returns:
- *  - 0 on success
- *  - a positive value if the new entry is older than the currently stored
- *    entry (in this case, no update will happen)
- *  - a negative value on error
- */
-int
-sdb_store_metric_attr(const char *hostname, const char *metric,
-		const char *key, const sdb_data_t *value, sdb_time_t last_update);
-
-/*
- * sdb_store_fetch_timeseries:
- * Fetch the time-series described by the specified host's metric and
- * serialize it as JSON into the provided string buffer.
- *
- * Returns:
- *  - 0 on success
- *  - a negative value else
- */
-int
-sdb_store_fetch_timeseries(const char *hostname, const char *metric,
-		sdb_timeseries_opts_t *opts, sdb_strbuf_t *buf);
-
-/*
- * sdb_store_get_field:
- * Get the value of a stored object's queryable field. The caller is
- * responsible for freeing any dynamically allocated memory possibly stored in
- * the returned value. If 'res' is NULL, the function will return whether the
- * field exists.
- *
- * Note: Retrieving the backend this way is not currently supported.
- *
- * Returns:
- *  - 0 on success
- *  - a negative value else
+ * sdb_store_metric_t represents the meta-data of a stored metric object.
  */
-int
-sdb_store_get_field(sdb_store_obj_t *obj, int field, sdb_data_t *res);
+typedef struct {
+	const char *hostname;
+	const char *name;
 
-/*
- * sdb_store_get_attr:
- * Get the value of a stored object's attribute. The caller is responsible for
- * freeing any dynamically allocated memory possibly stored in the returned
- * value. If 'res' is NULL, the function will return whether the attribute
- * exists. If specified, only attributes matching the filter will be
- * considered.
- *
- * Returns:
- *  - 0 if the attribute exists
- *  - a negative value else
- */
-int
-sdb_store_get_attr(sdb_store_obj_t *obj, const char *name, sdb_data_t *res,
-		sdb_store_matcher_t *filter);
+	/* All data stores providing this metric. */
+	const sdb_metric_store_t *stores;
+	size_t stores_num;
 
-/*
- * sdb_store_expr_create:
- * Creates an arithmetic expression implementing the specified operator on the
- * specified left and right operand.
- *
- * Returns:
- *  - an expression object on success
- *  - NULL else
- */
-sdb_store_expr_t *
-sdb_store_expr_create(int op, sdb_store_expr_t *left, sdb_store_expr_t *right);
+	sdb_time_t last_update;
+	sdb_time_t interval;
+	const char * const *backends;
+	size_t backends_num;
+} sdb_store_metric_t;
+#define SDB_STORE_METRIC_INIT { NULL, NULL, NULL, 0, 0, 0, NULL, 0 }
 
 /*
- * sdb_store_expr_fieldvalue:
- * Creates an expression which evaluates to the value of the specified
- * queryable field of a stored object.
- *
- * Returns:
- *  - an expression object on success
- *  - NULL else
+ * sdb_store_attribute_t represents a stored attribute.
  */
-sdb_store_expr_t *
-sdb_store_expr_fieldvalue(int field);
+typedef struct {
+	const char *hostname; /* optional */
+	int parent_type;
+	const char *parent;
+	const char *key;
+	sdb_data_t value;
 
-/*
- * sdb_store_expr_attrvalue:
- * Creates an expression which evaluates to the value of the specified
- * attribute of a stored object. Evaluates to a NULL value if the attribute
- * does not exist.
- *
- * Returns:
- *  - an expression object on success
- *  - NULL else
- */
-sdb_store_expr_t *
-sdb_store_expr_attrvalue(const char *name);
+	sdb_time_t last_update;
+	sdb_time_t interval;
+	const char * const *backends;
+	size_t backends_num;
+} sdb_store_attribute_t;
+#define SDB_STORE_ATTRIBUTE_INIT { NULL, 0, NULL, NULL, SDB_DATA_INIT, 0, 0, NULL, 0 }
 
 /*
- * sdb_store_expr_constvalue:
- * Creates an expression which evaluates to the specified constant value.
+ * A JSON formatter converts stored objects into the JSON format.
+ * See http://www.ietf.org/rfc/rfc4627.txt
  *
- * Returns:
- *  - an expression object on success
- *  - NULL else
+ * A JSON formatter object inherits from sdb_object_t and, thus, may safely be
+ * cast to a generic object.
  */
-sdb_store_expr_t *
-sdb_store_expr_constvalue(const sdb_data_t *value);
+struct sdb_store_json_formatter;
+typedef struct sdb_store_json_formatter sdb_store_json_formatter_t;
 
 /*
- * sdb_store_expr_eval:
- * Evaluate an expression for the specified stored object and stores the
- * result in 'res'. The result's value will be allocated dynamically if
- * necessary and, thus, should be free'd by the caller (e.g. using
- * sdb_data_free_datum). The object may be NULL, in which case the expression
- * needs to evaluate to a constant value. If specified, only objects matching
- * the filter will be used during the evaluation.
+ * A store writer describes the interface for plugins implementing a store.
  *
- * Returns:
+ * Any of the call-back functions shall return:
  *  - 0 on success
- *  - a negative value else
- */
-int
-sdb_store_expr_eval(sdb_store_expr_t *expr, sdb_store_obj_t *obj,
-		sdb_data_t *res, sdb_store_matcher_t *filter);
-
-/*
- * sdb_store_isnull_matcher:
- * Creates a matcher matching NULL values.
- */
-sdb_store_matcher_t *
-sdb_store_isnull_matcher(sdb_store_expr_t *expr);
-
-/*
- * sdb_store_isnnull_matcher:
- * Creates a matcher matching non-NULL values.
- */
-sdb_store_matcher_t *
-sdb_store_isnnull_matcher(sdb_store_expr_t *expr);
-
-/*
- * sdb_store_any_matcher:
- * Creates a matcher iterating over objects of the specified type. It matches
- * if *any* of those objects match 'm'.
- */
-sdb_store_matcher_t *
-sdb_store_any_matcher(int type, sdb_store_matcher_t *m);
-
-/*
- * sdb_store_all_matcher:
- * Creates a matcher iterating over objects of the specified type. It matches
- * if *all* of those objects match 'm'.
- */
-sdb_store_matcher_t *
-sdb_store_all_matcher(int type, sdb_store_matcher_t *m);
-
-/*
- * sdb_store_lt_matcher, sdb_store_le_matcher, sdb_store_eq_matcher,
- * sdb_store_ge_matcher, sdb_store_gt_matcher:
- * Create conditional matchers comparing the values of two expressions. The
- * matcher matches if the left expression compres less than, less or equal
- * than, equal to, not equal to, greater or equal than, or greater than the
- * right expression.
- */
-sdb_store_matcher_t *
-sdb_store_lt_matcher(sdb_store_expr_t *left, sdb_store_expr_t *right);
-sdb_store_matcher_t *
-sdb_store_le_matcher(sdb_store_expr_t *left, sdb_store_expr_t *right);
-sdb_store_matcher_t *
-sdb_store_eq_matcher(sdb_store_expr_t *left, sdb_store_expr_t *right);
-sdb_store_matcher_t *
-sdb_store_ne_matcher(sdb_store_expr_t *left, sdb_store_expr_t *right);
-sdb_store_matcher_t *
-sdb_store_ge_matcher(sdb_store_expr_t *left, sdb_store_expr_t *right);
-sdb_store_matcher_t *
-sdb_store_gt_matcher(sdb_store_expr_t *left, sdb_store_expr_t *right);
-
-/*
- * sdb_store_in_matcher:
- * Creates a matcher which matches if the right value evaluates to an array
- * value and the left value is included in that array. See sdb_data_inarray
- * for more details.
- */
-sdb_store_matcher_t *
-sdb_store_in_matcher(sdb_store_expr_t *left, sdb_store_expr_t *right);
-
-/*
- * sdb_store_regex_matcher:
- * Creates a matcher which matches the string value the left expression
- * evaluates to against the regular expression the right expression evaluates
- * to. The right expression may either be a constant value regular expression
- * or string or a dynamic value evaluating to a string. In the latter case,
- * the string is compiled to a regex every time the matcher is executed.
- */
-sdb_store_matcher_t *
-sdb_store_regex_matcher(sdb_store_expr_t *left, sdb_store_expr_t *right);
-
-/*
- * sdb_store_nregex_matcher:
- * Creates a regex matcher just like sdb_store_regex_matcher except that it
- * matches in case the regular expression does not match.
- */
-sdb_store_matcher_t *
-sdb_store_nregex_matcher(sdb_store_expr_t *left, sdb_store_expr_t *right);
-
-/*
- * sdb_store_matcher_op_cb:
- * Callback constructing a matcher operator.
- */
-typedef sdb_store_matcher_t *(*sdb_store_matcher_op_cb)
-	(sdb_store_expr_t *, sdb_store_expr_t *);
-
-/*
- * sdb_store_parse_matcher_op:
- * Parse a matcher operator and return a constructor for the respective
- * matcher.
- *
- * Returns:
- *  - matcher operator constructor on success
- *  - NULL else
- */
-sdb_store_matcher_op_cb
-sdb_store_parse_matcher_op(const char *op);
-
-/*
- * sdb_store_parse_object_type:
- * Parse the type name of a stored object.
- *
- * Returns:
- *  - the object type on success
- *  - a negative value else
- */
-int
-sdb_store_parse_object_type(const char *name);
-
-/*
- * sdb_store_parse_object_type_plural:
- * Parse the type name (plural) of a stored object.
- *
- * Returns:
- *  - the object type on success
- *  - a negative value else
- */
-int
-sdb_store_parse_object_type_plural(const char *name);
-
-/*
- * sdb_store_parse_field_name:
- * Parse the name of a stored object's queryable field.
- *
- * Returns:
- *  - the field id on success
- *  - a negative value else
- */
-int
-sdb_store_parse_field_name(const char *name);
-
-/*
- * sdb_store_dis_matcher:
- * Creates a matcher matching the disjunction (logical OR) of two matchers.
- */
-sdb_store_matcher_t *
-sdb_store_dis_matcher(sdb_store_matcher_t *left, sdb_store_matcher_t *right);
-
-/*
- * sdb_store_con_matcher:
- * Creates a matcher matching the conjunction (logical AND) of two matchers.
- */
-sdb_store_matcher_t *
-sdb_store_con_matcher(sdb_store_matcher_t *left, sdb_store_matcher_t *right);
-
-/*
- * sdb_store_con_matcher::
- * Creates a matcher matching the inverse (logical NOT) of a matcher.
- */
-sdb_store_matcher_t *
-sdb_store_inv_matcher(sdb_store_matcher_t *m);
-
-/*
- * sdb_store_matcher_matches:
- * Check whether the specified matcher matches the specified store object. If
- * specified, the filter will be used to preselect objects for further
- * evaluation. It is applied to any object that's used during the evaluation
- * of the matcher. Only those objects matching the filter will be considered.
- *
- * Note that the filter is applied to all object types (hosts, service,
- * metric, attribute). Thus, any object-specific matchers are mostly unsuited
- * for this purpose and, if used, may result in unexpected behavior.
- *
- * Returns:
- *  - 1 if the object matches
- *  - 0 else
- */
-int
-sdb_store_matcher_matches(sdb_store_matcher_t *m, sdb_store_obj_t *obj,
-		sdb_store_matcher_t *filter);
-
-/*
- * sdb_store_lookup_cb:
- * Lookup callback. It is called for each matching object when looking up data
- * in the store passing on the lookup filter and the specified user-data. The
- * lookup aborts early if the callback returns non-zero.
+ *  - a positive value if the new entry is older than the currently stored
+ *    entry (in this case, no update will happen)
+ *  - a negative value on error
  */
-typedef int (*sdb_store_lookup_cb)(sdb_store_obj_t *obj,
-		sdb_store_matcher_t *filter, void *user_data);
-
-/*
- * sdb_store_scan:
- * Look up objects of the specified type in the store. The specified callback
- * function is called for each object in the store matching 'm'. The function
- * performs a full scan of all objects stored in the database. If specified,
- * the filter will be used to preselect objects for further evaluation. See
- * the description of 'sdb_store_matcher_matches' for details.
- *
- * Returns:
- *  - 0 on success
- *  - a negative value else
+typedef struct {
+	/*
+	 * store_host:
+	 * Add/update a host in the store. If the host, identified by its
+	 * canonicalized name, already exists, it will be updated according to the
+	 * specified name and timestamp. Else, a new entry will be created in the
+	 * store.
+	 */
+	int (*store_host)(sdb_store_host_t *host, sdb_object_t *user_data);
+
+	/*
+	 * store_service:
+	 * Add/update a service in the store. If the service, identified by its
+	 * name, already exists for the specified host, it will be updated
+	 * according to the specified name and timestamp. If the referenced host
+	 * does not exist, an error will be reported. Else, a new entry will be
+	 * created in the store.
+	 */
+	int (*store_service)(sdb_store_service_t *service, sdb_object_t *user_data);
+
+	/*
+	 * store_metric:
+	 * Add/update a metric in the store. If the metric, identified by its
+	 * name, already exists for the specified host, it will be updated
+	 * according to the specified attributes. If the referenced host does not
+	 * exist, an error will be reported. Else, a new entry will be created in
+	 * the store.
+	 */
+	int (*store_metric)(sdb_store_metric_t *metric, sdb_object_t *user_data);
+
+	/*
+	 * store_attribute:
+	 * Add/update a host's attribute in the store. If the attribute,
+	 * identified by its key, already exists for the specified host, it will
+	 * be updated to the specified values. If the referenced host does not
+	 * exist, an error will be reported. Else, a new entry will be created in
+	 * the store.
+	 */
+	int (*store_attribute)(sdb_store_attribute_t *attr, sdb_object_t *user_data);
+} sdb_store_writer_t;
+
+/*
+ * A store reader describes the interface to query a store implementation.
  */
-int
-sdb_store_scan(int type, sdb_store_matcher_t *m, sdb_store_matcher_t *filter,
-		sdb_store_lookup_cb cb, void *user_data);
-
-/*
- * Flags for serialization functions.
- *
- * By default, the full host object will be included in the serialized output.
- * When specifying any of the flags, the respective information will be left
- * out. The SKIP_EMPTY flags may be used to skip host objects entirely.
+typedef struct {
+	/*
+	 * prepare_query:
+	 * Prepare the query described by 'ast' for execution.
+	 */
+	sdb_object_t *(*prepare_query)(sdb_ast_node_t *ast,
+			sdb_strbuf_t *errbuf, sdb_object_t *user_data);
+
+	/*
+	 * 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. The query result will be passed back via the specified
+	 * store writer.
+	 */
+	int (*execute_query)(sdb_object_t *q,
+			sdb_store_writer_t *w, sdb_object_t *wd,
+			sdb_strbuf_t *errbuf, sdb_object_t *user_data);
+} sdb_store_reader_t;
+
+/*
+ * Flags for JSON formatting.
  */
 enum {
-	SDB_WANT_ARRAY              = 1 << 0,
-
-	SDB_SKIP_ATTRIBUTES         = 1 << 0,
-	SDB_SKIP_SERVICES           = 1 << 1,
-	SDB_SKIP_METRICS            = 1 << 2,
-	SDB_SKIP_SERVICE_ATTRIBUTES = 1 << 3,
-
-	SDB_SKIP_ALL                = (1 << 8) - 1,
-
-	/* skip hosts if they do not reference any services/metrics */
-	SDB_SKIP_EMPTY_SERVICES     = 1 << 8,
-	SDB_SKIP_EMPTY_METRICS      = 1 << 9,
+	SDB_WANT_ARRAY = 1 << 0,
 };
 
-/*
- * sdb_store_tojson:
- * Serialize the entire store to JSON and append the result to the specified
- * buffer. If specified, only objects matching the filter will be included in
- * the result (see sdb_store_host_tojson for details).
- *
- * Returns:
- *  - 0 on success
- *  - a negative value on error
- */
-int
-sdb_store_tojson(sdb_strbuf_t *buf, sdb_store_matcher_t *filter, int flags);
-
-/*
- * sdb_store_host_tojson:
- * Serialize a host object to JSON and append the result to the specified
- * buffer. If specified, only objects matching the filter will be included in
- * the result. The filter is applied to each object individually and, thus,
- * should not be of any object-type specific kind. The filter is never applied
- * to the specified host object; the caller is responsible for this and for
- * correctly handling skipped hosts.
- *
- * Returns:
- *  - 0 on success
- *  - a negative value on error
- */
-int
-sdb_store_host_tojson(sdb_store_obj_t *host, sdb_strbuf_t *buf,
-		sdb_store_matcher_t *filter, int flags);
-
 /*
  * sdb_store_json_formatter:
  * Create a JSON formatter for the specified object types writing to the
@@ -629,43 +263,6 @@ sdb_store_host_tojson(sdb_store_obj_t *host, sdb_strbuf_t *buf,
 sdb_store_json_formatter_t *
 sdb_store_json_formatter(sdb_strbuf_t *buf, int type, int flags);
 
-/*
- * sdb_store_json_emit:
- * Serialize a single object to JSON adding it to the string buffer associated
- * with the formatter object. The serialized object will not include
- * attributes or any child objects. Instead, call the function again for each
- * of those objects. All attributes have to be emitted before any other
- * children types. Use sdb_store_json_emit_full() to emit a full (filtered)
- * object.
- *
- * Note that the output might not be valid JSON before calling
- * sdb_store_json_finish().
- *
- * Returns:
- *  - 0 on success
- *  - a negative value else
- */
-int
-sdb_store_json_emit(sdb_store_json_formatter_t *f, sdb_store_obj_t *obj);
-
-/*
- * sdb_store_json_emit_full:
- * Serialize a single object including it's attributes and all children to
- * JSON, adding it to the string buffer associated with the formatter object.
- * The filter, if specified, is applied to each attribute and child object.
- * Only matching objects will be included in the output.
- *
- * Note that the output might not be valid JSON before calling
- * sdb_store_json_finish().
- *
- * Returns:
- *  - 0 on success
- *  - a negative value else
- */
-int
-sdb_store_json_emit_full(sdb_store_json_formatter_t *f, sdb_store_obj_t *obj,
-		sdb_store_matcher_t *filter);
-
 /*
  * sdb_store_json_finish:
  * Finish the JSON output. This function has to be called once after emiting
@@ -674,6 +271,13 @@ sdb_store_json_emit_full(sdb_store_json_formatter_t *f, sdb_store_obj_t *obj,
 int
 sdb_store_json_finish(sdb_store_json_formatter_t *f);
 
+/*
+ * sdb_store_json_writer:
+ * A store writer implementation that generates JSON output. It expects a
+ * store JSON formatter as its user-data argument.
+ */
+extern sdb_store_writer_t sdb_store_json_writer;
+
 #ifdef __cplusplus
 } /* extern "C" */
 #endif