C Kan Quotes

Det kan du stole på. Liker du detektivfortellinger? Det gjør jeg. Jeg leser alle sammen, og har navnetrekkene til Dorothy Sayers og Agatha Christie og Dickson Carr og H.C. Bailey.

så lad det være den største forbryder, han er dog et menneske som jeg; også han har været uskyldig! Hvem veed, hvor mange haarde kampe han kjæmpede, før han gjorde det første skridt til sin ulykke; lidt efter lidt gled han dybere, - pludselig bliver ingen en forbryder: det ere lidenskaber, opdragelse og en forunderlig sammenkjædning af omstændigheder, som danner vores livs malerie, - vi maa afskye forbryderens handlinger, men kan menneskeligheden dadles om den beklager ham? Hvem veed hvorledes vi havde handlet, om vi vare fødte i hans stilling, med hans lidenskaber og begreber?

Net zoals Hitler de Brand van de Reichstag in de schoenen schoof van Marinus Vander Lubbe en zo een grote schoonmaak begon te houden in Duitsland, schuift Erdogan de coup geheel gratuit in de schoenen van Gülen om voortdurend mensen (het zijn er al meer dan 9.000!) te laten oppakken. Zijn zuiveringsactie, waadrbij de scheiding der machten niet langer wordt gerespecteerd, loopt geheel parallel met die van Hitler. Maar omdat Turkije lid is van de Navo kan Erdogan straks een spil slaan tussen Rusland en Amerika, genoeg voor een derde wereldoorlog. Natuurlijk wordt het prutsleger van Erdogan dan onder de zoden gelopen door het Russische leger, maar dan zal hij de hulp inroepen van zijn Navo-bondgenoot Amerika. Erdogan is met zijn dubbele agenda zowat de grootste bedreiging voor de wereldvrede en de Belgische Turken die nu achter hem staan kunnen straks gevaarlijke collaborateurs worden. Dus heren politici als het waar is dat 'gouverner c'est prévoir', begin dan maar nu met het terugsturen van al die domme Turkse oproepkraaiers in ons land naar het land van hun aanbeden Erdogan.

Nogle lægemidler kan være nyttige nogle gange for nogle patienter, især i den akutte fase, hvor en patient kan være så plaget af panik eller vrangforestillinger, at det kan være nyttigt at dæmpe følelserne med noget beroligende. Men medmindre lægerne bliver meget bedre til at bruge psykofarmaka - hvilket vil sige at bruge dem meget lidt, i lave doser og altid med en plan for udtrapning - så ville vore borgere være langt bedre stillet, hvis vi fjernede alle psykofarmaka fra markedet.

Subtile forskelle kan være vigtige. Hvis hendes psykiater havde sagt: " Du er en person, der for tiden har symptomer, som vi normalt kalder skizofreni", ville det have indikeret, at personen stadig var der og var så meget andet end sine symptomer, og at sygdommen ikke nødvendigvis ville vare resten af livet, hvilket desværre ofte er psykiaternes opfattelse.

Der er flere grunde - men få gode- til, hvorfor mange psykiatriske patienter har flere diagnoser. For det første er de diagnostiske kriterier meget brede og meget uspecifikke for de problemer, patienterne har. For det andet er der en masse overlapning mellem de forskellige diagnostiske kategorier og en tilbøjelighed til, at tilstanden kan ændre sig med tiden til noget andet. Dette kaldes ofte komorbiditet, selvom problemet ikke er, at patienten har flere 'sygdomme', men at sygdommene er så vagt definerede, at det er ligesom, hvis en biolog ser en skygge på lang afstand og siger: 'Det er en elefant og en gnu og muligvis et næsehorn'. For det tredje bliver medicinbivirkninger ofte fejlfortolket som nye sygdomme. Ordinering af ét lægemiddel kan derfor ofte føre til ordinering af andre typer lægemidler på en kaskadelignende måde. [...] Læger er nødt til at indse, at det er umuligt at vurdere, om en patient virkelig har disse yderligere 'sygdomme', så længe patienten er under indflydelse af hjerneaktivitet kemikalier. Skadevirkningerne kan komme og gå, hvilket er en vigtig grund til, at folk tror, det ikke kan være lægemidlet. På denne måde kan ikke blot den rutinemæssige behandling, men også forsøg på at nedtrappe et lægemiddel - som ofte fremkalder disse bivirkninger - føre til flere diagnoser, flere stoffer og mere skade.

Jeg har et problem med at acceptere, at alder er en risikofaktor for noget som helst. Vi kan jo ikke sænke vores risiko ved at ændre vores dåbsattest, så det er ikke nogen modificerbar risikofaktor, men en uundgåelig konsekvens af at blive ved med at overleve. Hvis nogen insisterer på at kalde alder en risikofaktor, vil jeg insistere på, at fødslen er en risikofaktor, der med 100% sikkerhed fører til døden på et eller andet tidspunkt.

På lang sigt overstiger de skadelige virkninger af psykofarmaka de gavnlige. Sådan er det ikke for psykoterapi. En god psykoterapeut kan undertiden opnå bemærkelsesværdige resultater, der kan holde resten af livet uden bivirkninger

Medicinen kan løse problemer for skolerne, men ikke for børnene, der blot agerer på en måde, der generer de voksne, hvilket i høj grad er netop de 'symptomer', der definerer børne-ADHD.

Ideen om, at det er tilladt at medicinere inkompetente menneske mod deres vilje, ender i den slags omgivelser med at blive begrundelsen for at medicinere alle, der ikke er enige. Det kan ikke forsvares ud fra et etisk perspektiv, da det -helt objektivt- som regel ikke er i personens bedste interesse. Desuden drejer det sig om patientens autonomi, hvilket ikke er en alt-eller intet-tilstand. Folk kan være inkompetente i nogle henseende og ikke i andre

Alles wat mogelijk is, vraagt erom te bestaan en zou bij gevolg ook bestaan, als niet iets anders dat er ook om vraagt te bestaan en dat niet tegelijk met het eerste kan bestaan, dat tegenhield. - Gottfried Wilhelm Leibniz

Marco Polo descrive un ponte, pietra per pietra. – Ma qual è la pietra che sostiene il ponte? – chiede Kublai Kan. – Il ponte non è sostenuto da questa o da quella pietra, – risponde Marco, – ma dalla linea dell’arco che esse formano. Kublai Kan rimase silenzioso, riflettendo. Poi soggiunse: – Perché mi parli delle pietre? È solo dell’arco che mi importa. Polo risponde: – Senza pietre non c’è arco.

In Cassandra, however, sorting is by design because you must determine how to compare data for a column family at the time of its creation. The comparator of the column family dictates how the rows are ordered on reads. Additionally, columns are ordered by their column names, also by a comparator.

The maximum size of a column key is 64 KB, in contrast to 2 GB for a column value.

Because one row can hold as many as 2 billion variable columns.

Wide row It is common to use wide rows for ordering, grouping and efficient filtering. Besides, you can use skinny rows. All you have to consider is the number of columns the row contains. It is worth noting that for a column family storing skinny rows, the column key is repeatedly stored in each column. Although it wastes some storage space, it is not a problem on inexpensive commodity hard disks.

Given a sufficiently long period of time without further changes, all the updates can be expected to propagate throughout the cluster and the replicas on all the nodes will be consistent eventually. In real life, an update takes only a fraction of a second to become eventually consistent. In other words, it is a trade-off between consistency and latency.

Bloom filter Bloom filter is a sample subset of the primary index with very fast nondeterministic algorithms to check whether an element is a member of a set. It is used to boost the performance.

On the flip side, the following figure shows the components and their sequence of executions that form a read path: Cassandra read path

Column Column is the smallest data model element and storage unit in Cassandra. Though it also exists in a relational database, it is a different thing in Cassandra. As shown in the following figure, a column is a name-value pair with a timestamp and an optional Time-To-Live (TTL) value:

Since the write operation is log-based and memory-based, it does not involve any read operation, and therefore the write operation can be extremely fast.

If a failure happens, the commitlog can be used to replay the sequence of the write operations to merge the data that persists in the SSTables.

Read operation is also very efficient by looking up the data in the memory store and the indexed SSTables, which are then merged to return the data.

The replication factor per data center is set to three here. With two data centers, there are six replicas in total.

For write operations, Cassandra supports tunable consistency by various write consistency levels. The write consistency level is the number of replicas that acknowledge a successful write. It is tunable on a spectrum of write consistency levels, as shown in the following figure: Cassandra write consistency levels

Another repair mechanism is called anti-entropy which is a replica synchronization mechanism to ensure up-to-date data on all nodes and is run by the administrators manually.

Conversely, Cassandra is designed to work in a massive-scale, distributed environment in which ACID compliance is difficult to achieve, and replication is a must.

A query is always the starting point of designing a Cassandra data model. As an analogy, a query is a question and the data model is the answer.

A snitch determines which data centers and racks to go for in order to make Cassandra aware of the network topology for routing the requests efficiently.

A value of the timeuuid data type is a Type 1 UUID which includes the time of its generation and is sorted by timestamp. It is therefore ideal for use in applications requiring conflict-free timestamps. A valid timeuuid uses the time in 100 intervals since 00:00:00.00 UTC (60 bits), a clock sequence number for prevention of duplicates (14 bits), and the IEEE 801 MAC address (48 bits) to generate a unique identifier, for example, 74754ac0-e13f-11e3-a8a3-a92bc9056ee6.

In a distributed system backed by Cassandra, we should minimize unnecessary network traffic as much as possible. In other words, the lesser the number of nodes the query needs to work with, the better the performance of the data model. We must cater to the cluster topology as well as the physical storage of the data model.

The data that is being updated is then written to a memory structure, known as memtable.

When the memtable is full, the data inside the memtable is flushed to a disk storage structure, SSTable.

The writes are automatically partitioned by the row key and replicated to the other nodes holding the same partition.

The ability to scale horizontally and incrementally is a Cassandra key design feature.

The following figure depicts the components and their sequence of executions that form a write path: Cassandra write path

No sequence In a relational database, sequences are usually used to generate unique values for a surrogate key. Cassandra has no sequences because it is extremely difficult to implement in a peer-to-peer distributed system. There are however workarounds, which are as follows: Using part of the data to generate a unique key Using a UUID In most cases, the best practice is to select the second workaround.

Hinted handoff aims at reducing the time to restore a failed node when rejoining the cluster. It ensures absolute write availability by sacrificing a bit of read consistency. If a replica is down at the time a write occurs, another healthy replica stores a hint. Even worse, if all the relevant replicas are down, the coordinator stores the hint locally. The hint basically contains the location of the failed replica, the affected row key, and the actual data that is being written. When a node responsible for the token range is up again, the hint will be handed off to resume the write. As such, the update cannot be read before a complete handoff, leading to inconsistent reads.

implies that there can be short intervals of inconsistency among the replicated nodes during which the data gets updated among these nodes. In other words, the replicas are updated asynchronously.

Cassandra is a column-family store and provides great schemaless flexibility to application developers.

Cassandra borrows the commitlog mechanism from Google BigTable to ensure data durability.

It also checks all the remaining replicas in the background. If a replica is found to be inconsistent, the coordinator will issue an update to bring back the consistency. This mechanism is called read repair.

Features of Cassandra In order to keep this chapter short, the following bullet list covers the great features provided by Cassandra: Written in Java and hence providing native Java support Blend of Google BigTable and Amazon Dynamo Flexible schemaless column-family data model Support for structured and unstructured data Decentralized, distributed peer-to-peer architecture Multi-data center and rack-aware data replication Location transparent Cloud enabled Fault-tolerant with no single point of failure An automatic and transparent failover Elastic, massively, and linearly scalable Online node addition or removal High Performance Built-in data compression Built-in caching layer Write-optimized Tunable consistency providing choices from very strong consistency to different levels of eventual consistency Provision of Cassandra Query Language (CQL), a SQL-like language imitating INSERT, UPDATE, DELETE, SELECT syntax of SQL Open source and community-driven

If no time zone is specified, the time zone of the Cassandra coordinator node handing the write request is used. Therefore the best practice is to specify the time zone with the timestamp rather than relying on the time zone configured on the Cassandra nodes to avoid any ambiguities.

The Map data structure gives efficient key lookup, and the sorted nature provides efficient scans. RowKey is a unique key and can hold a value. The inner SortedMap data structure allows a variable number of ColumnKey values. This is the trick that Cassandra uses to be schemaless and to allow the data model to evolve organically over time. It should be noted that each column has a client-supplied timestamp associated, but it can be ignored during data modeling. Cassandra uses the timestamp internally to resolve transaction conflicts.

Instead, it encourages and performs best when the data model is denormalized.

Cassandra has no sequences because it is extremely difficult to implement in a peer-to-peer distributed system.

The most important difference is that a relational database models data by relationships whereas Cassandra models data by query.

When a read request comes in to a node, the data to be returned is merged from all the related SSTables and any unflushed memtables. Timestamps are used to determine which one is up-to-date. The merged value is also stored in a write-through row cache to improve the future read performance.

Dynamo introduces a mechanism called Eventual Consistency to support consistency. Temporary inconsistency might occur in the cluster at a point in time, but eventually all the nodes will receive the latest consistent updates.

The node location can be determined by the rack and data center with reference to the node's IP address.

Cassandra uses a very efficient algorithm, called Phi Accrual Failure Detection Algorithm, to detect the failure of a node. The idea of the algorithm is that the failure detection is not represented by a Boolean value stating whether a node is up or down. Instead, the algorithm outputs a value on the continuous suspicion level between dead and alive, on how confident it is that the node has failed.

The commitlog is purged after the flush.

Different names in columns are possible in different rows. That is why Cassandra is both row oriented and column oriented. It should be remarked that there is no timestamp for rows.

Cassandra is now 5 years old. It is an active open source project in the Apache Software Foundation and therefore it is known as Apache Cassandra as well. Cassandra can manage huge volume of structured, semi-structured, and unstructured data in a large distributed cluster across multiple data centers. It provides linear scalability, high performance, fault tolerance, and supports a very flexible data model.

Brott kan föda romantik.

Hoe zijn vrienden hem noemden kan ik je niet vertellen, want die had hij niet.