Обсуждение: Query unable to utilize index without typecast to fixed length character

Hello,

We have encountered an unexpected quirk with our DB and we are unsure if this is expected behaviour or an issue.

PG version PostgreSQL 14.3 on aarch64-unknown-linux-gnu, compiled by aarch64-unknown-linux-gnu-gcc (GCC) 7.4.0, 64-bit

schema of table in question and related indexes

CREATE TABLE public.marketplace_sale (
    log_index integer NOT NULL,
    created_at timestamp with time zone DEFAULT now() NOT NULL,
    updated_at timestamp with time zone DEFAULT now() NOT NULL,
    block_timestamp timestamp with time zone NOT NULL,
    block bigint NOT NULL,
    contract_address character(42) NOT NULL,
    buyer_address character(42) NOT NULL,
    seller_address character(42) NOT NULL,
    transaction_hash character(66) NOT NULL,
    quantity numeric NOT NULL,
    token_id numeric NOT NULL,
    seller_amount_wei numeric,
    marketplace_fees_wei numeric DEFAULT 0,
    royalty_fees_wei numeric DEFAULT 0,
    data_source text NOT NULL,
    marketplace text,
    original_data jsonb,
    source_discriminator text,
    total_amount_wei numeric NOT NULL,
    unique_hash bytea GENERATED ALWAYS AS (sha512((((((((((transaction_hash)::text || (block)::text) || (log_index)::text) || (contract_address)::text) || (token_id)::text) || (buyer_address)::text) || (seller_address)::text) || (quantity)::text))::bytea)) STORED NOT NULL,
    CONSTRAINT buyer_address_lower CHECK (((buyer_address)::text = lower((buyer_address)::text))),
    CONSTRAINT buyer_address_prefix CHECK (starts_with((buyer_address)::text, '0x'::text)),
    CONSTRAINT contract_address_lower CHECK (((contract_address)::text = lower((contract_address)::text))),
    CONSTRAINT contract_address_prefix CHECK (starts_with((contract_address)::text, '0x'::text)),
    CONSTRAINT seller_address_lower CHECK (((seller_address)::text = lower((seller_address)::text))),
    CONSTRAINT seller_address_prefix CHECK (starts_with((seller_address)::text, '0x'::text)),
    CONSTRAINT transaction_hash_lower CHECK (((transaction_hash)::text = lower((transaction_hash)::text))),
    CONSTRAINT transaction_hash_prefix CHECK (starts_with((transaction_hash)::text, '0x'::text))
);

ALTER TABLE ONLY public.marketplace_sale
    ADD CONSTRAINT marketplace_sale_pkey PRIMARY KEY (unique_hash);

CREATE INDEX sales_contract_blocktimestamp_idx ON public.marketplace_sale USING btree (contract_address, block_timestamp);

CREATE INDEX sales_contract_date_idx ON public.marketplace_sale USING btree (contract_address, token_id, block_timestamp);

When running this query

EXPLAIN(verbose, costs, buffers) with token_pairs(contract_address, token_id)  as (
  values ('0xed5af388653567af2f388e6224dc7c4b3241c544', '1375'::numeric ), ('0xed5af388653567af2f388e6224dc7c4b3241c544', '4'::numeric )
)
select sales.* from token_pairs, LATERAL (
select
  contract_address, token_id,
  block_timestamp, total_amount_wei, buyer_address,
  seller_address, block, quantity, transaction_hash
  from marketplace_sale
where                        
(marketplace_sale.contract_address, marketplace_sale.token_id) = (token_pairs.contract_address, token_pairs.token_id)
order by contract_address desc, token_id desc, block_timestamp desc
limit 1                      
) sales;

we get the query plan

                                                                                                                                                   QUERY PLAN                                                                                                                                                  
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Nested Loop  (cost=0.69..332764.78 rows=2 width=231)
   Output: marketplace_sale.contract_address, marketplace_sale.token_id, marketplace_sale.block_timestamp, marketplace_sale.total_amount_wei, marketplace_sale.buyer_address, marketplace_sale.seller_address, marketplace_sale.block, marketplace_sale.quantity, marketplace_sale.transaction_hash
   ->  Values Scan on "*VALUES*"  (cost=0.00..0.03 rows=2 width=64)
         Output: "*VALUES*".column1, "*VALUES*".column2
   ->  Limit  (cost=0.69..166382.36 rows=1 width=231)
         Output: marketplace_sale.contract_address, marketplace_sale.token_id, marketplace_sale.block_timestamp, marketplace_sale.total_amount_wei, marketplace_sale.buyer_address, marketplace_sale.seller_address, marketplace_sale.block, marketplace_sale.quantity, marketplace_sale.transaction_hash
         ->  Index Scan Backward using sales_contract_date_idx on public.marketplace_sale  (cost=0.69..3660397.27 rows=22 width=231)
               Output: marketplace_sale.contract_address, marketplace_sale.token_id, marketplace_sale.block_timestamp, marketplace_sale.total_amount_wei, marketplace_sale.buyer_address, marketplace_sale.seller_address, marketplace_sale.block, marketplace_sale.quantity, marketplace_sale.transaction_hash
               Index Cond: (marketplace_sale.token_id = "*VALUES*".column2)
               Filter: ((marketplace_sale.contract_address)::text = "*VALUES*".column1)
 Query Identifier: 8815736494208428864
 Planning:
   Buffers: shared hit=4
(13 rows)

As you can see it is unable to fully utilize the (contract_address, token_id, block_timestamp) index and can only use the token_id column as the index condition.

However if we explicitly cast the contract values in the values list to varchar or character(42)

Like so

EXPLAIN(verbose, costs, buffers) with token_pairs(contract_address, token_id)  as (
  values ('0xed5af388653567af2f388e6224dc7c4b3241c544'::varchar, '1375'::numeric ), ('0xed5af388653567af2f388e6224dc7c4b3241c544'::varchar, '4'::numeric )
)
select sales.* from token_pairs, LATERAL (
select
  contract_address, token_id,
  block_timestamp, total_amount_wei, buyer_address,
  seller_address, block, quantity, transaction_hash
  from marketplace_sale
where                        
(marketplace_sale.contract_address, marketplace_sale.token_id) = (token_pairs.contract_address, token_pairs.token_id)
order by contract_address desc, token_id desc, block_timestamp desc
limit 1                      
) sales;

It can now use the index

                                                                                                                                                   QUERY PLAN                                                                                                                                                  
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Nested Loop  (cost=0.69..17.49 rows=2 width=231)
   Output: marketplace_sale.contract_address, marketplace_sale.token_id, marketplace_sale.block_timestamp, marketplace_sale.total_amount_wei, marketplace_sale.buyer_address, marketplace_sale.seller_address, marketplace_sale.block, marketplace_sale.quantity, marketplace_sale.transaction_hash
   ->  Values Scan on "*VALUES*"  (cost=0.00..0.03 rows=2 width=64)
         Output: "*VALUES*".column1, "*VALUES*".column2
   ->  Limit  (cost=0.69..8.71 rows=1 width=231)
         Output: marketplace_sale.contract_address, marketplace_sale.token_id, marketplace_sale.block_timestamp, marketplace_sale.total_amount_wei, marketplace_sale.buyer_address, marketplace_sale.seller_address, marketplace_sale.block, marketplace_sale.quantity, marketplace_sale.transaction_hash
         ->  Index Scan Backward using sales_contract_date_idx on public.marketplace_sale  (cost=0.69..8.71 rows=1 width=231)
               Output: marketplace_sale.contract_address, marketplace_sale.token_id, marketplace_sale.block_timestamp, marketplace_sale.total_amount_wei, marketplace_sale.buyer_address, marketplace_sale.seller_address, marketplace_sale.block, marketplace_sale.quantity, marketplace_sale.transaction_hash
               Index Cond: ((marketplace_sale.contract_address = ("*VALUES*".column1)::bpchar) AND (marketplace_sale.token_id = "*VALUES*".column2))
 Query Identifier: -5527103051535383406
 Planning:
   Buffers: shared hit=4
(12 rows)

We were expecting behaviour similar to 

explain (verbose, costs, buffers) select * from marketplace_sale where
contract_address = '0xed5af388653567af2f388e6224dc7c4b3241c544'
and token_id = '1375'
order by contract_address desc, token_id desc, block_timestamp desc
limit 1;
                                                                                                                                                        QUERY PLAN                                                                                                                                                        
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=0.69..6.04 rows=1 width=1610)
   Output: log_index, created_at, updated_at, block_timestamp, block, contract_address, buyer_address, seller_address, transaction_hash, quantity, token_id, seller_amount_wei, marketplace_fees_wei, royalty_fees_wei, data_source, marketplace, original_data, source_discriminator, total_amount_wei, unique_hash
   ->  Index Scan Backward using sales_contract_date_idx on public.marketplace_sale  (cost=0.69..16.74 rows=3 width=1610)
         Output: log_index, created_at, updated_at, block_timestamp, block, contract_address, buyer_address, seller_address, transaction_hash, quantity, token_id, seller_amount_wei, marketplace_fees_wei, royalty_fees_wei, data_source, marketplace, original_data, source_discriminator, total_amount_wei, unique_hash
         Index Cond: ((marketplace_sale.contract_address = '0xed5af388653567af2f388e6224dc7c4b3241c544'::bpchar) AND (marketplace_sale.token_id = '1375'::numeric))
 Query Identifier: -2069211501626469745
 Planning:
   Buffers: shared hit=2
(8 rows)

Any insight into why this happens would be greatly appreciated