181–190 of 231 posts
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> I was advocating for it for decades, but everyone dismisses it with “you don’t know better than rdbms”. That’s almost a religion. Which is simply not true. Query optimization is done heuristically, for the simple reason that you usually need to run the query to get the information required for "perfect" optimization. If the RDBMS really knew better, it wouldn't offer query hints.
Postgres doesn't offer query hints. ;)
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4. lots of small building blocks of static machine code precompiled/shipped with DB software binary, later iterated & looped through based on the query plan the optimizer came up with. Oracle does this with their columnar/vector/SIMD processing In-Memory Database option (it's not like LLVM as it doesn't compile/link/rearrange the existing binary building blocks, just jumps & loops through the existing ones in the req…
That’s a really cool idea! Is there any writeups or articles about this in more detail?
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the b5000 was one of the first non -virtual stack machines, but its instruction set isn't any more of a virtual machine than the 8088's or the pdp-10's. there were a number of interpreted stack languages in the 50s, though not nearly as many as there would be later
When one does digital archeology is it quite common to see Assembly referred to as bytecode, when the CPUs are actually interpreters written in microcode. Another example, all the Xerox PARC workstations, which loaded the respective interpreter (Smalltalk, Interlisp, Mesa, Mesa/Cedar) into the CPU as first step during the boot process.
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I love how the example SQL query uses abbreviated columns that sound like runes: select -- count(*) a.mandt, b.rldnr, a.bukrs, a.gjahr, a.belnr, b.docln, a.buzei -- * from BSEG as a innerjoin ACDOCA as b on b.rclnt = a.mandt and b.rbukrs = a.bukrs and b.gjahr = a.gjahr and b.belnr = a.belnr where a.mandt = '715' and b.rldnr = '0L' and b.docln = '000001' and a.buzei = '001' and a.gjahr = '2018' --and a.gjahr = '2017'…
yeah, these accounting table field names have not changed since around 30 years, which is not necessarily a bad thing... for a human readable view of this you can look e.g. here https://docsfortec.com/sap/S4/tables/ACDOCA
Did they start out with German table names and decide to give new tables English names at some point?
I think most people associate bytecode VMs / interpreters with general-purpose programming languages, but it's a surprisingly useful concept in other contexts. Sometimes bytecode VMs appear in unexpected places! A few that I'm aware of: - eBPF, an extension mechanism in the Linux kernel - DWARF expression language, with interpreters in debuggers like GDB and LLDB - The RAR file format includes a bytecode encoding for…
Any sufficiently complicated C or Fortran program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp.
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VMs really can be. They have a long history in code portability. In the old days it really wasn't uncommon to use an approach centered around some interpretable byte code running in a vm, where the reusable vm was all that needed porting to different architectures and operating systems. This all happened well before Java. It was really big in gaming, Zork, Sierra games, LucasArts games, and even a few more "action" g…
Don't know about Flashback, but Another World famously was VM based.
I think most people associate bytecode VMs / interpreters with general-purpose programming languages, but it's a surprisingly useful concept in other contexts. Sometimes bytecode VMs appear in unexpected places! A few that I'm aware of: - eBPF, an extension mechanism in the Linux kernel - DWARF expression language, with interpreters in debuggers like GDB and LLDB - The RAR file format includes a bytecode encoding for…
The original TeX Fonts stored their metrics in TFM (short for TeX font metrics) files, which contains a bytecode interpreter for calculating ligatures and kerning between characters. I learned about that when I tried reading the files myself. From what I can tell, modern fonts using OpenType just have tables to accomplish something similar now, in the form of the GSUB and GPOS tables? Documentation for the TFM format…
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Typically you get XML for showplan because it can represent the tree structure better.
You get XML for estimated execution plans if you use SET SHOWPLAN_XML ON. You get the actual execution plan XML along with your results if you use SET STATISTICS XML. You can see cached execution plans in the sys.dm_exec_query_plan dynamic management view. The estimated/actual execution plan feature in SQL Server Management Studio was changed to use XML in SQL Server 2005. The SQL Server team are only adding new info…
I second your longing for something more detailed than explain query plan in Sqlite though.
In fact I complained about it here and some sqlite developer pointed me to these resources:
https://news.ycombinator.com/item?id=30405275
I've never actually tried yet. Queries are still too fast to do all that:)
SQLite's design docs were the first time I had seen a database use a virtual machine instead of walking a tree. I later noticed VMs in libraries, embedded DSLs, and other applications outside of large general-purpose programming languages. That really drove home for me that VMs could be anywhere and were often a useful step in handling a user's expressions.
[1] https://stratos.seas.harvard.edu/files/MonetDebull2012.pdf
[2] https://www.researchgate.net/publication/220538804_Database_...
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I don’t doubt the author, but what is it that makes rendering a tree of objects to a table a difficult problem? Is that not what browsers do when they render a table element?
Quote from the article: "A tree-of-objects representation is more difficult to publish in a human-readable form. The objects that comprise the tree tend to all be very different, and thus it is tricky to come up with a consistent and simple table representation with which to display the objects. Any any such table representation that you do come up with would almost certainly have more than six columns, probably many…