ovsdb-idl: idl compound indexes implementation

This patch adds support for the creation of multicolumn indexes
in the C IDL to enable for efficient search and retrieval of database
rows by key.

Signed-off-by: Esteban Rodriguez Betancourt <estebarb@hpe.com>
Co-authored-by: Lance Richardson <lrichard@redhat.com>
Signed-off-by: Lance Richardson <lrichard@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

lib/ovsdb-idl-provider.h

@@ -1,4 +1,5 @@
 /* Copyright (c) 2009, 2010, 2011, 2012, 2016 Nicira, Inc.
+ * Copyright (C) 2016 Hewlett Packard Enterprise Development LP
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -111,6 +112,7 @@ struct ovsdb_idl_table {
     struct hmap rows;        /* Contains "struct ovsdb_idl_row"s. */
     struct ovsdb_idl *idl;   /* Containing idl. */
     unsigned int change_seqno[OVSDB_IDL_CHANGE_MAX];
+    struct shash indexes;    /* Contains "struct ovsdb_idl_index"s */
     struct ovs_list track_list; /* Tracked rows (ovsdb_idl_row.track_node). */
     struct ovsdb_idl_condition condition;
     bool cond_changed;
@@ -122,6 +124,33 @@ struct ovsdb_idl_class {
     size_t n_tables;
 };
 
+/*
+ * Structure containing the per-column configuration of the index.
+ */
+struct ovsdb_idl_index_column {
+    const struct ovsdb_idl_column *column; /* Column used for index key. */
+    column_comparator *comparer; /* Column comparison function. */
+    int sorting_order; /* Sorting order (ascending or descending). */
+};
+
+/*
+ * Defines a IDL compound index
+ */
+struct ovsdb_idl_index {
+    struct skiplist *skiplist;    /* Skiplist with pointers to rows. */
+    struct ovsdb_idl_index_column *columns; /* Columns configuration */
+    size_t n_columns;             /* Number of columns in index. */
+    size_t alloc_columns;         /* Size allocated memory for columns,
+                                     comparers and sorting order. */
+    bool ins_del;                 /* True if a row in the index is being
+                                     inserted or deleted; if true, the
+                                     search key is augmented with the
+                                     UUID and address in order to discriminate
+                                     between entries with identical keys. */
+    const struct ovsdb_idl_table *table; /* Table that owns this index */
+    const char *index_name;       /* The name of this index. */
+};
+
 struct ovsdb_idl_row *ovsdb_idl_get_row_arc(
     struct ovsdb_idl_row *src,
     const struct ovsdb_idl_table_class *dst_table,