extracted objects

docs/packages/PLJSON_OBJECT_CACHE.md

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+# PLJSON_OBJECT_CACHE
+
+## Package Specification
+
+```sql
+package pljson_object_cache as
+
+  /* E.I.Sarmas (github.com/dsnz)   2020-04-18   object cache to speed up internal operations */
+
+  /* !!! NOTE: this package is used internally by pljson and it's not part of the api !!! */
+
+  /* index by string of "id.path" or "path" */
+  type pljson_element_tab is table of pljson_element index by varchar2(250);
+
+  last_id number := 0;
+  pljson_element_cache pljson_element_tab;
+  cache_reqs number := 0;
+  cache_hits number := 0;
+  cache_invalid_reqs number := 0;
+
+  type vset is table of varchar2(1) index by varchar2(250);
+  names_set vset;
+
+  procedure set_names_set(names pljson_varray);
+  function in_names_set(a_name varchar2) return boolean;
+
+  procedure reset;
+  procedure flush;
+  procedure print_stats;
+  function next_id return number;
+  function object_key(elem pljson_element, piece varchar2) return varchar2;
+  function get(key varchar2) return pljson_element;
+  procedure set(key varchar2, val pljson_element);
+end;```
+
+## Package Body
+
+```sql
+package body pljson_object_cache as
+
+  /* E.I.Sarmas (github.com/dsnz)   2020-04-18   object cache to speed up internal operations */
+
+  /* !!! NOTE: this package is used internally by pljson and it's not part of the api !!! */
+
+  procedure set_names_set(names pljson_varray) is
+  begin
+    if names.COUNT = 0 then
+      return;
+    end if;
+    for i in names.FIRST .. names.LAST loop
+      names_set(names(i)) := '1';
+    end loop;
+  end;
+
+  function in_names_set(a_name varchar2) return boolean is
+  begin
+    if names_set.exists(a_name) then
+      return true;
+    else
+      return false;
+    end if;
+  end;
+
+  procedure reset is
+  begin
+    last_id := 0;
+    flush;
+  end;
+
+  procedure flush is
+  begin
+    pljson_element_cache.delete;
+    cache_reqs := 0;
+    cache_hits := 0;
+    cache_invalid_reqs := 0;
+  end;
+
+  procedure print_stats is
+  begin
+    dbms_output.put_line('reqs = ' || cache_reqs);
+    dbms_output.put_line('hits = ' || cache_hits);
+    dbms_output.put_line('invalid reqs = ' || cache_invalid_reqs);
+    dbms_output.put_line('cache count = ' || pljson_element_cache.count);
+    dbms_output.put_line('id count = ' || last_id);
+  end;
+
+  function next_id return number is
+  begin
+    last_id := last_id + 1;
+    return last_id;
+  end;
+
+  function object_key(elem pljson_element, piece varchar2) return varchar2 is
+    key varchar2(250);
+  begin
+    if elem.object_id is null or elem.object_id = 0 then
+      cache_invalid_reqs := cache_invalid_reqs + 1;
+      return null;
+    end if;
+    key := to_char(elem.object_id)||'.'||piece;
+    return key;
+  end;
+
+  function get(key varchar2) return pljson_element is
+    cache_key varchar2(32767);
+  begin
+    cache_key := key;
+    if cache_key is null then
+      cache_key := '$';
+    end if;
+    cache_reqs := cache_reqs + 1;
+    if pljson_element_cache.exists(cache_key) then
+      cache_hits := cache_hits + 1;
+      return pljson_element_cache(cache_key);
+    else
+      return null;
+    end if;
+  end;
+
+  procedure set(key varchar2, val pljson_element) is
+    cache_key varchar2(32767);
+  begin
+    cache_key := key;
+    if cache_key is null then
+      cache_key := '$';
+    end if;
+    --dbms_output.put_line('caching: ' || cache_key);
+    pljson_element_cache(cache_key) := val;
+  end;
+
+  /*
+  -- experimental, ignore
+  -- to use with 'get_json_element'
+
+  function get_piece(elem pljson, piece varchar2) return pljson_element is
+    key varchar2(250);
+    val pljson_element;
+  begin
+    key := object_cache.object_key(elem, piece);
+    if key is null then
+      return elem.get(piece);
+    end if;
+    val := object_cache.get(key);
+    if val is not null then
+      return val;
+    else
+      val := elem.get(piece);
+      object_cache.set(key, val);
+      return val;
+    end if;
+  end;
+
+  function get_piece(elem pljson_list, piece varchar2) return pljson_element is
+    key varchar2(250);
+    val pljson_element;
+  begin
+    key := object_cache.object_key(elem, piece);
+    if key is null then
+      return elem.get(piece);
+    end if;
+    val := object_cache.get(key);
+    if val is not null then
+      return val;
+    else
+      val := elem.get(piece);
+      object_cache.set(key, val);
+      return val;
+    end if;
+  end;
+  */
+end;```