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Tag Archives: Databases

Reactive Database Access – Part 3 – Using jOOQ with Scala, Futures and Actors

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We’re very happy to continue our a guest post series on the jOOQ blog by Manuel Bernhardt. In this blog series, Manuel will explain the motivation behind so-called reactive technologies and after introducing the concepts of Futures and Actors use them in order to access a relational database in combination with jOOQ. Manuel Bernhardt is an independent software consultant with ...

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Using the JDBC Insert Features in Oracle

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Introduction In this article I will show an example of how to use the JDBC bulk insert features supported by Oracle — and which are specific to Oracle. For more details on why one might like to resort to using bulk inserts in general, e.g., performance considerations when certain circumstances warrant, see the JCG article, “JDBC Batch Insert Example ” ...

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Safe Database Migration Pattern Without Downtime

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I’ve been doing a continuous delivery talk for a while now and during my talk I describe a pattern of how to safely migrating one database to another database without downtime. Since many people contacted me and asked for more details about it, I will describe it here in more details as promised. You can use this pattern to migrate ...

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Does PostgreSQL Have an ORA-01795-like Limit?

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The Oracle database requires that no more than 1000 entries be used in a SQL IN portion of a WHERE clause and will throw an ORA-01795 error if that number is exceeded. If a value needs to be compared to more than 1000 values, approaches other than use of IN must be applied. I wondered if this limitation applies to ...

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A beginner’s guide to read and write skew phenomena

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Introduction In my article about ACID and database transactions, I introduced the three phenomena described by the SQL standard: dirty read non-repeatable read phantom read While these are good to differentiate the four isolation levels (Read Uncommitted, Read Committed, Repeatable Read and Serializable), in reality, there are more phenomena to take into consideration as well. The 1995 paper (A Critique ...

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How to Quickly Enumerate Indexes in Oracle 11gR2

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Do you want to know real quick what kind of indexes there are on any given table in your Oracle schema? Nothing simpler than that. Just run the following query: SELECT i.index_name, listagg(c.column_name, ', ') WITHIN GROUP (ORDER BY c.column_position) AS columns FROM all_indexes i JOIN all_ind_columns c ON i.index_name = c.index_name WHERE i.table_name = 'FILM_ACTOR' GROUP BY i.index_name The ...

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Single Quotes in Oracle Database Index Column Specification

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In my previous post, I mentioned that a downside of using double quotes to explicitly specify case in Oracle identifiers is the potential for being confused with the use of single quotes for string literals. Although I don’t personally think this is sufficient reason to avoid use of double quotes for identifiers in Oracle, it is worth being aware of ...

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Downsides of Mixed Identifiers When Porting Between Oracle and PostgreSQL Databases

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Both the Oracle database and the PostgreSQL database use the presence or absence of double quotes to indicate case sensitive or case insensitive identifiers. Each of these databases allows identifiers to be named without quotes (generally case insensitive) or with double quotes (case sensitive). This blog post discusses some of the potential negative consequences of mixing quoted (or delimited) identifiers ...

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Benchmarking Aurora vs MySQL: Is Amazon’s New DB Really 5x Faster?

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Amazon Aurora: The next generation of hosted database services put to the test In this post we’re taking a closer look at Amazon Aurora to see how it fares against MySQL and if it delivers on the promise of a 5x performance boost. Recently reaching general availability, Aurora is Amazon’s home grown MySQL compatible database. Currently available on three AWS regions ...

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