On Wed, Mar 9, 2016 at 1:10 PM, Alexander Farber <alexander.far...@gmail.com > wrote:
> Hello fellow PostgreSQL users, > > what is please the most efficient way to delete a slice from the start of > a longer array (after I have copied it to another array)? > > Do I really have to copy a large slice of the array to itself, like in the > last line here: > > pile_array := pile_array || swap_array; > > /* here I copy away swap_len elements */ > new_hand := pile_array[1:swap_len]; > > /* here I don't know how to efficiently remove already copied > elements */ > pile_array := pile_array[(swap_len + 1):ARRAY_LENGTH(pile_array, > 1)]; > > or is there a better way? > This looks like something for card hands? What you are doing seems correct to me. > > Thank you > Alex > > P.S. The listing of the entire stored function in question: > > CREATE OR REPLACE FUNCTION words_swap_game( > IN in_uid integer, > IN in_gid integer, > IN in_swap varchar(7)) > RETURNS void AS > $func$ > DECLARE > i integer; > j integer; > swap_len integer; > hand_len integer; > pile_len integer; > swap_array varchar[]; > pile_array varchar[]; > old_hand varchar[]; > new_hand varchar[]; > hand_ignore boolean[]; > BEGIN > swap_array := STRING_TO_ARRAY(in_swap, NULL); > swap_len := ARRAY_LENGTH(swap_array, 1); > > SELECT hand1, pile, ARRAY_LENGTH(hand1, 1), ARRAY_LENGTH(pile, 1) > INTO old_hand, pile_array, hand_len, pile_len > FROM words_games > WHERE gid = in_gid > AND player1 = in_uid > /* and it is first player's turn */ > AND (played1 IS NULL OR played1 < played2); > > IF NOT FOUND THEN > SELECT hand2, pile, ARRAY_LENGTH(hand2, 1), > ARRAY_LENGTH(pile, 1) > INTO old_hand, pile_array, hand_len, pile_len > FROM words_games > WHERE gid = in_gid > AND player2 = in_uid > /* and it is second player's turn */ > AND (played2 IS NULL OR played2 < played1); > END IF; > > pile_array := pile_array || swap_array; > -- pile_array := words_shuffle(pile_array); > new_hand := pile_array[1:swap_len]; > pile_array := pile_array[(swap_len + 1):pile_len]; /* XXX is it > good? */ > > hand_ignore := ARRAY_FILL(FALSE, ARRAY[hand_len]); > > <<hand_loop>> > FOR i IN 1..hand_len LOOP > FOR j IN 1..swap_len LOOP > IF hand_ignore[j] = FALSE AND > old_hand[i] = swap_array[j] THEN > hand_ignore[j] := TRUE; > CONTINUE hand_loop; > END IF; > END LOOP; > > new_hand := new_hand || old_hand[i]; > END LOOP; > /* > UPDATE words_games > SET hand1 = new_hand, > pile = pile_array, > played1 = CURRENT_TIMESTAMP > WHERE gid = in_gid > AND player1 = in_uid > -- and it is first player's turn > AND (played1 IS NULL OR played1 < played2); > > IF NOT FOUND THEN > UPDATE words_games > SET hand2 = new_hand, > pile = pile_array, > played2 = CURRENT_TIMESTAMP > WHERE gid = in_gid > AND player2 = in_uid > -- and it is second player's turn > AND (played2 IS NULL OR played2 < played1); > END IF; > */ > > END > $func$ LANGUAGE plpgsql; > > > > -- Best Wishes, Chris Travers Efficito: Hosted Accounting and ERP. Robust and Flexible. No vendor lock-in. http://www.efficito.com/learn_more
