PolarDB：Gunakan pemindaian indeks global dalam operasi DML

Penggunaan

• Buat tabel terpartisi dan indeks global:

  CREATE TABLE gi_ora
  (
      a int,
      b int,
      c int GENERATED ALWAYS AS (b * 2),
      d int DEFAULT 0,
      e int,
      f text,
      g text
  ) PARTITION BY RANGE (a)
  (
      partition p0 values less than (50),
      partition p1 values less than (100),
      partition p2 values less than (200),
      partition p3 values less than (300),
      partition p4 values less than (400),
      partition p5 values less than (500),
      partition p6 values less than (600),
      partition p7 values less than (700),
      partition p8 values less than (800)
  );
  
  INSERT INTO gi_ora(a,b,d,e,f,g) SELECT i,i,i, (random()*1000)::int,(random()*30000000)::int::text,(random()*30000000)::int::text FROM generate_series(1,799) i ;
  
  CREATE INDEX ON gi_ora(b) global;
  ANALYZE gi_ora;

• Gunakan pemindaian indeks global untuk melakukan operasi DELETE pada data yang ditentukan:

  EXPLAIN (costs off, verbose on)  DELETE FROM gi_ora WHERE b = 198;

  Keluaran serupa akan ditampilkan:

                                   QUERY PLAN
  ----------------------------------------------------------------------------
   DELETE ON global_index_dml.gi_ora
     ->  GLOBAL INDEX SCAN USING gi_ora_global_idx ON global_index_dml.gi_ora
           Output: gi_ora.tableoid, gi_ora.ctid
           Index Cond: (gi_ora.b = 198)
  (4 rows)

• Gunakan pemindaian indeks global untuk melakukan operasi UPDATE pada data yang ditentukan:

  EXPLAIN (costs off, verbose on)  UPDATE gi_ora SET a = a - 10 WHERE b = 198;

  Keluaran serupa akan ditampilkan:

                                   QUERY PLAN
  ----------------------------------------------------------------------------
   UPDATE ON global_index_dml.gi_ora
     ->  GLOBAL INDEX SCAN USING gi_ora_global_idx ON global_index_dml.gi_ora
           Output: (gi_ora.a - 10), gi_ora.tableoid, gi_ora.ctid
           Index Cond: (gi_ora.b = 198)
  (4 rows)