Two places
The Double: a fraud ring uses one card in two places at the same minute. Find the lender and their chain.
task
Find cards with taps at two different stations within 2 minutes of each other.
Play
lessons
Intro
Expressions
Null
Joins
Set Operations
Dates
Aggregates
Subqueries
Window Functions
Changing Data
Ctes Recursion
Explain
Analytics
Schema Design
Types
Sequences Identity Uuid
Transactions
Views
Functions Triggers
Indexes
Partitioning
Jsonb
Ranges
Full Text Search
Copy
Rls Roles
Catalogs
- [ ] 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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