Count the customers
Your first case is a warm-up. The shop database holds one row per customer. Count them.
task
How many customers does the shop have?
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- [ ] What pg_class says about a table
- [ ] Column layout in pg_attribute
- [ ] The index behind a primary key
- [ ] Count your table's forks
- [ ] Statistics on a boolean function
- [ ] Extended statistics on virtual generated columns
- [ ] Clear one extended statistics object
- [ ] Clear statistics of a missing table
- [ ] pg_stats knows the table oid
- [ ] Boss: one row about a table
Heap Pages
Mvcc
Vacuum
- [ ] Line pointers across DELETE and VACUUM
- [ ] The visibility map after VACUUM
- [ ] relfrozenxid advances
- [ ] VACUUM FULL gives the space back
- [ ] A fresh file after REPACK
- [ ] A read sets all-visible without VACUUM
- [ ] REPACK (CONCURRENTLY)
- [ ] REPACK USING INDEX orders the heap
- [ ] A partitioned table needs an index name
- [ ] Which table would autovacuum pick
- [ ] Dead-item memory in VACUUM VERBOSE
- [ ] Boss: one VACUUM cycle
Hot
Toast
Btree
- [ ] BRIN ranges
- [ ] Physical correlation
- [ ] GIN pending list
- [ ] Index-only scans and Heap Fetches
- [ ] Skip scan on a B-tree
- [ ] B-tree meta page
- [ ] Walk the root page
- [ ] A lookup reads few pages
- [ ] Random inserts leave leaf pages loose
- [ ] IS NOT DISTINCT FROM reaches the index
- [ ] Boss: count a group from the index
Buffers
Wal
Planner
- [ ] Read-stream counters in EXPLAIN (IO)
- [ ] Read the Memoize estimate
- [ ] Generic or custom plan
- [ ] IS NULL on any NOT NULL column of the inner side
- [ ] Turn eager aggregation off
- [ ] IS NOT DISTINCT FROM reaches the index
- [ ] An impossible predicate
- [ ] COALESCE stops at the first NOT NULL argument
- [ ] Incremental sort under Append
- [ ] Memoize under an anti join
- [ ] Read generated plan advice
- [ ] Force a nested loop with advice
- [ ] Pin a plan without touching the query
- [ ] Generic and custom plan counters
Statistics
Locks
Amcheck
What Changed In 19
- [ ] SUPPORT clause for aggregates
- [ ] URL-safe tokens
- [ ] Promote a NOT ENFORCED check
- [ ] CHECKPOINT takes options
- [ ] DO SELECT without RETURNING
- [ ] Skip a two-line header
- [ ] JSON has no header
- [ ] HEADER n is for reading only
- [ ] COPY TO from a partitioned table
- [ ] Keep the row, null the bad value
- [ ] IS NOT DISTINCT FROM NULL on a NOT NULL column
- [ ] Aggregate before the join
- [ ] Choose the grantor
- [ ] A scalar subquery over a grouping expression
- [ ] GROUPING() inside a subquery
- [ ] GiST on inet needs no extension
- [ ] IS JSON on a domain
- [ ] JIT is off by default
- [ ] JSON_ARRAY(query) on an empty set
- [ ] jsonpath string methods
- [ ] CR and LF in database, role and tablespace names
- [ ] NOT IN becomes an anti join
- [ ] A nullable column keeps the SubPlan
- [ ] Validate oid8 input
- [ ] psql \pset display_true
- [ ] psql prompt %S
- [ ] random() over dates
- [ ] regdatabase
- [ ] REPACK (CONCURRENTLY)
- [ ] REPACK USING INDEX orders the heap
- [ ] A partitioned table needs an index name
- [ ] A foreign key to a table defined later
- [ ] standard_conforming_strings cannot be turned off
- [ ] SET list = NULL
- [ ] Skip scan
- [ ] New and renamed stemmers
- [ ] CREATE SUBSCRIPTION ... SERVER
- [ ] No overlapping shifts, enforced
- [ ] Rows per heap page
- [ ] bytea to uuid
- [ ] The length must be 16 bytes
- [ ] Virtual generated columns
- [ ] Change a virtual column without a rewrite
- [ ] The CHECK still guards the new formula
- [ ] WAIT FOR LSN
- [ ] IGNORE NULLS is not for every window function
- [ ] Boss: repair a table with two 19 features
Club Drills
- [ ] Classify facilities by upkeep
- [ ] Format member names
- [ ] Facilities with many slots booked
- [ ] Members per surname initial
- [ ] Add a facility
- [ ] Facilities with Wall in the name
- [ ] Bookings per month
- [ ] Recommendations made by each member
- [ ] Members who have recommended someone
- [ ] Slots booked per facility
Club Counting
Upsert Drills
editor
results
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