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    <title>DEV Community: Oleh Nahornyi</title>
    <description>The latest articles on DEV Community by Oleh Nahornyi (@olehnahornyi).</description>
    <link>https://dev.to/olehnahornyi</link>
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      <title>DEV Community: Oleh Nahornyi</title>
      <link>https://dev.to/olehnahornyi</link>
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    <item>
      <title>Keyword Era is Over: Build Search Visibility with Fast Linked Data Entities for GEO</title>
      <dc:creator>Oleh Nahornyi</dc:creator>
      <pubDate>Wed, 10 Dec 2025 08:18:18 +0000</pubDate>
      <link>https://dev.to/olehnahornyi/keyword-era-is-over-build-search-visibility-with-fast-linked-data-entities-for-geo-1n94</link>
      <guid>https://dev.to/olehnahornyi/keyword-era-is-over-build-search-visibility-with-fast-linked-data-entities-for-geo-1n94</guid>
      <description>&lt;p&gt;Search engines are racing away from keyword hunting toward discovering complete knowledge entities. Up to 99% of an average page’s code is service noise: pleasant for humans, useless for a bot. We’ve long “seasoned” texts with keywords like spices, but that kitchen is closed—generative engines want the dish itself, a coherent data object that fits directly into their knowledge base.&lt;/p&gt;

&lt;p&gt;For an AI crawler the knowledge graph behind a page matters most: who owns or sells the product, what exactly it is, where it is used, what value it brings. And there is one brutal rule: if your page renders longer than 300 milliseconds, your chance of being read is close to zero—almost like hoping to win EuroMillions.&lt;/p&gt;

&lt;p&gt;&lt;a href="https://github.com/oleg578/pure-renderer-ld" rel="noopener noreferrer"&gt;Pure-renderer-ld&lt;/a&gt; is built for this reality. It turns a page into a compact static document and describes it as an entity using LinkedData (&lt;a href="https://schema.org/" rel="noopener noreferrer"&gt;Schema.org&lt;/a&gt;). Everything superfluous dissolves; meaning and relationships stay. The final version is served in under 300 ms—those few milliseconds decide whether the page is indexed or ignored. Speed here is not performance vanity; it is the cost of admission to a world where bots skim millions of URLs per second.&lt;/p&gt;

&lt;p&gt;Pre-release tests say more than theory. We took leading Shopify and Odoo pages. One page shrank from 3172.9 KB to 13.8 KB (‑99.6%, about 230× lighter). A catalog dropped from 5569.2 KB to 149.8 KB, roughly 37× faster to deliver. Another page slid to 65.0 KB (‑86.5%), and yet another to 95.6 KB (‑89.1%). Even a synthetic “fakeshop” behaved: 12.4 KB became 4.2 KB. Behind the numbers is a clear sensation—bots receive static HTML with no JavaScript or CSS overhead, and they receive it almost instantly.&lt;/p&gt;

&lt;p&gt;Visibility is where the payoff appears. The service reads meta tags and generates a LinkedData script (JSON-LD from schema.org). Each page emerges as a finished entity with properties and links that generative systems understand. A bot no longer guesses what matters; it sees a map of relations and drops it into its own graph. Sub‑300 ms static delivery lowers the risk of timeouts, and rich structured data makes snippets more persuasive. Clicks rise not through keyword stuffing but because the search engine trusts the meaning of the page and shows it plainly.&lt;/p&gt;

&lt;p&gt;The method also calms the production line. A single approach to cleaning and describing content lets teams scale catalogs, blogs, and marketplaces without endless manual tweaking. CDN traffic shrinks, render load falls, A/B cycles speed up, and the team stops arguing about “where to cram two more keywords,” returning to the product’s essence.&lt;/p&gt;

&lt;p&gt;The workflow is straightforward, though the engineering is not. The service cleans HTML, removes the div-soup, extracts the entity of a product, article, or card, describes it via Linked Data, “bakes” the page into a static response, and serves it to bots. The result is predictable quality and stable behavior: always light, always structured, always explainable to AI.&lt;/p&gt;

&lt;p&gt;If you want search engines to perceive your product the way they expect to, try pure-renderer-ld. It turns every page into a valuable data entity—fast, transparent, and free of excess code—and gives your business the rare luxury of speaking to search in the language of meaning instead of a dialect of random attributes.&lt;/p&gt;

&lt;p&gt;The service is ready to run as a proxy or alongside a caching layer and comes with logging and utilization monitoring out of the box.&lt;/p&gt;

&lt;p&gt;&lt;a href="https://github.com/oleg578/pure-renderer-ld" rel="noopener noreferrer"&gt;https://github.com/oleg578/pure-renderer-ld&lt;/a&gt;&lt;/p&gt;

</description>
      <category>seo</category>
    </item>
    <item>
      <title>Three ways to fetch SQL data in Go</title>
      <dc:creator>Oleh Nahornyi</dc:creator>
      <pubDate>Wed, 02 Oct 2024 08:46:03 +0000</pubDate>
      <link>https://dev.to/olehnahornyi/three-ways-to-fetch-sql-data-in-go-44pe</link>
      <guid>https://dev.to/olehnahornyi/three-ways-to-fetch-sql-data-in-go-44pe</guid>
      <description>&lt;h2&gt;
  
  
  Introduction
&lt;/h2&gt;

&lt;p&gt;In this article, we explore three different approaches to fetching data from SQL databases in Golang: the standard method using JSON marshaling, a dynamic approach using maps, and an optimized method that avoids unnecessary overhead.&lt;/p&gt;

&lt;p&gt;In my practice, there were very frequent cases where I had to retrieve data from a database with an unknown structure beforehand. This often happens in the e-commerce industry.&lt;/p&gt;

&lt;p&gt;We will consider 3 methods of retrieving data, along with their advantages and disadvantages.&lt;/p&gt;

&lt;p&gt;You can get all the code of the examples from the repository &lt;br&gt;
&lt;a href="https://github.com/oleg578/dbf" rel="noopener noreferrer"&gt;https://github.com/oleg578/dbf&lt;/a&gt;&lt;/p&gt;

&lt;p&gt;You can read the improved article here:&lt;br&gt;
&lt;a href="https://nahornyioleh.be/fetch-sql-data-in-go/" rel="noopener noreferrer"&gt;https://nahornyioleh.be/fetch-sql-data-in-go/&lt;/a&gt;&lt;/p&gt;
&lt;h2&gt;
  
  
  Data preparing
&lt;/h2&gt;

&lt;p&gt;We will use the database MariaDB, because I just like this database. It has never failed me in 10 years of practice with a load of up to 500 million transactions per day with a data volume of up to 4 terabytes in e-commerce. And it’s really faster than MySQL.&lt;/p&gt;

&lt;p&gt;Code for create MariaDB docker instance and seed test data are in &lt;a href="https://github.com/oleg578/dbf/tree/main/db" rel="noopener noreferrer"&gt;https://github.com/oleg578/dbf/tree/main/db&lt;/a&gt;&lt;/p&gt;

&lt;p&gt;All examples are tested on Ubuntu 24.04.1 LTS (Noble Numbat) with 11th Gen Intel Core i5–1135G7 and 16GiB RAM.&lt;/p&gt;
&lt;h2&gt;
  
  
  Standard way
&lt;/h2&gt;

&lt;p&gt;The standard way is trivial — we fetch rows from database into array and then Marshal it into JSON struct&lt;br&gt;
&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="n"&gt;rs&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;errRs&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;con&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;QueryContext&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;ctx&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;q&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;numbRows&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;

&lt;span class="o"&gt;...&lt;/span&gt;

 &lt;span class="k"&gt;for&lt;/span&gt; &lt;span class="n"&gt;rs&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Next&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
  &lt;span class="k"&gt;var&lt;/span&gt; &lt;span class="n"&gt;dmy&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="n"&gt;Dummy&lt;/span&gt;&lt;span class="p"&gt;{}&lt;/span&gt;
  &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;rs&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Scan&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;
   &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;dmy&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ID&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
   &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;dmy&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Product&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
   &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;dmy&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Description&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
   &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;dmy&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Price&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
   &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;dmy&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Qty&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
   &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;dmy&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Date&lt;/span&gt;&lt;span class="p"&gt;);&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
   &lt;span class="nb"&gt;panic&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;err&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
  &lt;span class="p"&gt;}&lt;/span&gt;
  &lt;span class="n"&gt;result&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="nb"&gt;append&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;result&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;dmy&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
 &lt;span class="p"&gt;}&lt;/span&gt;
 &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;rs&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Err&lt;/span&gt;&lt;span class="p"&gt;();&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
  &lt;span class="nb"&gt;panic&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;err&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
 &lt;span class="p"&gt;}&lt;/span&gt;
 &lt;span class="n"&gt;msg&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;errRTJ&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;json&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Marshal&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;result&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
 &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;errRTJ&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
  &lt;span class="nb"&gt;panic&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;errRTJ&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
 &lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="o"&gt;...&lt;/span&gt;

&lt;span class="n"&gt;_&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;errOut&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;os&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Stdout&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Write&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;msg&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
&lt;span class="o"&gt;...&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;


&lt;p&gt;What about speed?&lt;br&gt;
Test result:&lt;/p&gt;

&lt;p&gt;&lt;code&gt;% ./db2json_struct 10000000 1&amp;gt;/dev/null                                                                                           &lt;br&gt;
Elapsed time: 12631 ms, HeapAlloc = 5400.725 MB, Sys = 7099.447 MB&lt;br&gt;
10000000 records read&lt;/code&gt;&lt;/p&gt;

&lt;p&gt;Let’s just remember this as a starting point.&lt;/p&gt;
&lt;h2&gt;
  
  
  Using map way
&lt;/h2&gt;

&lt;p&gt;Next we consider fetching unknown list of columns — like “SELECT * FROM …”.&lt;br&gt;
The sequence of actions is simple.&lt;br&gt;
Each record will be represent as map[string]interface{}, then&lt;br&gt;
&lt;/p&gt;
&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="c"&gt;// create result slice&lt;/span&gt;
&lt;span class="c"&gt;// numbRows is number of rows in result&lt;/span&gt;
&lt;span class="n"&gt;outRows&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="nb"&gt;make&lt;/span&gt;&lt;span class="p"&gt;([]&lt;/span&gt;&lt;span class="k"&gt;map&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="kt"&gt;string&lt;/span&gt;&lt;span class="p"&gt;]&lt;/span&gt;&lt;span class="k"&gt;interface&lt;/span&gt;&lt;span class="p"&gt;{},&lt;/span&gt; &lt;span class="m"&gt;0&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;numbRows&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; 
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;


&lt;p&gt;We will not serialize each record to save program execution time, and our actions are not complex.&lt;br&gt;
See &lt;a href="https://github.com/oleg578/dbf/tree/mapping/example" rel="noopener noreferrer"&gt;https://github.com/oleg578/dbf/tree/mapping/example&lt;/a&gt;&lt;/p&gt;

&lt;p&gt;After fetch rows from database, we will request an slice of columns&lt;br&gt;
&lt;/p&gt;
&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="n"&gt;columns&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;rs&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Columns&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;


&lt;p&gt;Create slice of values and slice of pointers for data&lt;br&gt;
&lt;/p&gt;
&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="n"&gt;values&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="nb"&gt;make&lt;/span&gt;&lt;span class="p"&gt;([]&lt;/span&gt;&lt;span class="k"&gt;interface&lt;/span&gt;&lt;span class="p"&gt;{},&lt;/span&gt; &lt;span class="nb"&gt;len&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;columns&lt;/span&gt;&lt;span class="p"&gt;))&lt;/span&gt;
&lt;span class="n"&gt;valuePointers&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="nb"&gt;make&lt;/span&gt;&lt;span class="p"&gt;([]&lt;/span&gt;&lt;span class="k"&gt;interface&lt;/span&gt;&lt;span class="p"&gt;{},&lt;/span&gt; &lt;span class="nb"&gt;len&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;values&lt;/span&gt;&lt;span class="p"&gt;))&lt;/span&gt;
  &lt;span class="k"&gt;for&lt;/span&gt; &lt;span class="n"&gt;i&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="k"&gt;range&lt;/span&gt; &lt;span class="n"&gt;values&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;valuePointers&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="n"&gt;i&lt;/span&gt;&lt;span class="p"&gt;]&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;values&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="n"&gt;i&lt;/span&gt;&lt;span class="p"&gt;]&lt;/span&gt;
  &lt;span class="p"&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;


&lt;p&gt;Then for each row we get the map which represent model — &lt;a href="https://github.com/oleg578/dbf/blob/mapping/sql2json.go" rel="noopener noreferrer"&gt;https://github.com/oleg578/dbf/blob/mapping/sql2json.go&lt;/a&gt;&lt;br&gt;
&lt;/p&gt;
&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="n"&gt;Row2Map&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;columns&lt;/span&gt; &lt;span class="p"&gt;[]&lt;/span&gt;&lt;span class="kt"&gt;string&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;values&lt;/span&gt; &lt;span class="p"&gt;[]&lt;/span&gt;&lt;span class="k"&gt;interface&lt;/span&gt;&lt;span class="p"&gt;{})&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="k"&gt;map&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="kt"&gt;string&lt;/span&gt;&lt;span class="p"&gt;]&lt;/span&gt;&lt;span class="k"&gt;interface&lt;/span&gt;&lt;span class="p"&gt;{},&lt;/span&gt; &lt;span class="kt"&gt;error&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
 &lt;span class="n"&gt;rowMap&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="nb"&gt;make&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="k"&gt;map&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="kt"&gt;string&lt;/span&gt;&lt;span class="p"&gt;]&lt;/span&gt;&lt;span class="k"&gt;interface&lt;/span&gt;&lt;span class="p"&gt;{})&lt;/span&gt;
 &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="nb"&gt;len&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;columns&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="nb"&gt;len&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;values&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;errors&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;New&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"columns and values length not equal"&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
 &lt;span class="p"&gt;}&lt;/span&gt;
 &lt;span class="k"&gt;for&lt;/span&gt; &lt;span class="n"&gt;i&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;col&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="k"&gt;range&lt;/span&gt; &lt;span class="n"&gt;columns&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
  &lt;span class="n"&gt;rowMap&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="n"&gt;col&lt;/span&gt;&lt;span class="p"&gt;]&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="n"&gt;assignCellValue&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;values&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="n"&gt;i&lt;/span&gt;&lt;span class="p"&gt;])&lt;/span&gt; &lt;span class="c"&gt;// we will help to typify the value&lt;/span&gt;
 &lt;span class="p"&gt;}&lt;/span&gt;
 &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;rowMap&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="n"&gt;assignCellValue&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;val&lt;/span&gt; &lt;span class="k"&gt;interface&lt;/span&gt;&lt;span class="p"&gt;{})&lt;/span&gt; &lt;span class="k"&gt;interface&lt;/span&gt;&lt;span class="p"&gt;{}&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
 &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;b&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;ok&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;val&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="p"&gt;([]&lt;/span&gt;&lt;span class="kt"&gt;byte&lt;/span&gt;&lt;span class="p"&gt;);&lt;/span&gt; &lt;span class="n"&gt;ok&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
  &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;floatValue&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;strconv&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ParseFloat&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="kt"&gt;string&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;b&lt;/span&gt;&lt;span class="p"&gt;),&lt;/span&gt; &lt;span class="m"&gt;64&lt;/span&gt;&lt;span class="p"&gt;);&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;==&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
   &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;floatValue&lt;/span&gt;
  &lt;span class="p"&gt;}&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="kt"&gt;string&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;b&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
 &lt;span class="p"&gt;}&lt;/span&gt;
 &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;val&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;


&lt;p&gt;&lt;strong&gt;&lt;em&gt;Note:&lt;/em&gt;&lt;/strong&gt;&lt;br&gt;
&lt;em&gt;You may want to pay attention to the function assignCellValue — its purpose is to pre-assign a type to column values. Simple trick — this function tells the JSON encoder which values ​​to accept as non-numeric.&lt;/em&gt;&lt;br&gt;
Benchmark:&lt;br&gt;
&lt;code&gt;cpu: 11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz&lt;br&gt;
BenchmarkRow2Map&lt;br&gt;
BenchmarkRow2Map-8     7376358        159.0 ns/op      336 B/op        2 allocs/op&lt;/code&gt;&lt;/p&gt;

&lt;p&gt;Finally, execution time of our example — &lt;a href="https://github.com/oleg578/dbf/blob/mapping/example/main.go" rel="noopener noreferrer"&gt;https://github.com/oleg578/dbf/blob/mapping/example/main.go&lt;/a&gt;&lt;br&gt;
&lt;code&gt;% ./db2json_map 10000000 1&amp;gt;/dev/null&lt;br&gt;
Elapsed time: 12152 ms, HeapAlloc = 8966.899 MB, Sys = 12248.287 MB&lt;br&gt;
10000000 records read&lt;/code&gt;&lt;/p&gt;

&lt;p&gt;What can we say about these results?&lt;/p&gt;

&lt;p&gt;Benefits — We can obtain structures that are not predefined.&lt;/p&gt;

&lt;p&gt;Disadvantages — there are several.&lt;br&gt;
But we pay for this with memory consumption.&lt;br&gt;
It’s easy to see that such an implementation consumes 1.5 times more memory.&lt;/p&gt;

&lt;p&gt;The second disadvantage which can give us a headache are data types. We must define what we will access as numeric data, and what we will define as string. In current we use AssignValue auxiliary function:&lt;br&gt;
&lt;/p&gt;
&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="n"&gt;assignCellValue&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;val&lt;/span&gt; &lt;span class="k"&gt;interface&lt;/span&gt;&lt;span class="p"&gt;{})&lt;/span&gt; &lt;span class="k"&gt;interface&lt;/span&gt;&lt;span class="p"&gt;{}&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
 &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;b&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;ok&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;val&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="p"&gt;([]&lt;/span&gt;&lt;span class="kt"&gt;byte&lt;/span&gt;&lt;span class="p"&gt;);&lt;/span&gt; &lt;span class="n"&gt;ok&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
  &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;floatValue&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;strconv&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ParseFloat&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="kt"&gt;string&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;b&lt;/span&gt;&lt;span class="p"&gt;),&lt;/span&gt; &lt;span class="m"&gt;64&lt;/span&gt;&lt;span class="p"&gt;);&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;==&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
   &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;floatValue&lt;/span&gt;
  &lt;span class="p"&gt;}&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="kt"&gt;string&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;b&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
 &lt;span class="p"&gt;}&lt;/span&gt;
 &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;val&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;


&lt;p&gt;If value can be represented as float — then we define it as interface value (json library will define it as numeric or null), else as string.&lt;/p&gt;

&lt;p&gt;The third disadvantage is map structure property — we can’t guarantee order of fields in json. But this disadvantage may be unimportant.&lt;/p&gt;

&lt;p&gt;We cannot say that the result we got is satisfactory.He devours memory. On small datasets this may be acceptable, but this can negatively affect processing with large amounts of data.&lt;br&gt;
&lt;a href="https://github.com/oleg578/dbf/tree/mapping" rel="noopener noreferrer"&gt;https://github.com/oleg578/dbf/tree/mapping&lt;/a&gt;&lt;/p&gt;
&lt;h2&gt;
  
  
  What can we improve?
&lt;/h2&gt;

&lt;p&gt;Let’s look at the weak points in our algorithm of actions when we use maps.&lt;/p&gt;

&lt;p&gt;This a creating map[string]interface{} for each row — this very expensive operation in terms of resources and processor time;&lt;br&gt;
And another too expensive operation — JSON marshaling the final slice which can be very big.&lt;/p&gt;
&lt;h2&gt;
  
  
  It’s time to think about improvement
&lt;/h2&gt;
&lt;h3&gt;
  
  
  Let’s play with data structures
&lt;/h3&gt;

&lt;p&gt;When we get data from a table, the order of columns is always defined by the database. Then we can use 2 coordinated slices — columns and values. Then we can refuse a map type and use slice.&lt;/p&gt;

&lt;p&gt;The next trick — we will request data as byte slices and list of columns will fetch as list of ColumnTypes — it will help us in future.&lt;br&gt;
&lt;/p&gt;
&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="n"&gt;columns&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;rs&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ColumnTypes&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;
 &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
  &lt;span class="n"&gt;log&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Fatalf&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"fault get column types: %v"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
 &lt;span class="p"&gt;}&lt;/span&gt;
 &lt;span class="n"&gt;values&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="nb"&gt;make&lt;/span&gt;&lt;span class="p"&gt;([]&lt;/span&gt;&lt;span class="n"&gt;sql&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;RawBytes&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="nb"&gt;len&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;columns&lt;/span&gt;&lt;span class="p"&gt;))&lt;/span&gt;
 &lt;span class="n"&gt;valuePointers&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="nb"&gt;make&lt;/span&gt;&lt;span class="p"&gt;([]&lt;/span&gt;&lt;span class="k"&gt;interface&lt;/span&gt;&lt;span class="p"&gt;{},&lt;/span&gt; &lt;span class="nb"&gt;len&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;values&lt;/span&gt;&lt;span class="p"&gt;))&lt;/span&gt;
 &lt;span class="k"&gt;for&lt;/span&gt; &lt;span class="n"&gt;i&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="k"&gt;range&lt;/span&gt; &lt;span class="n"&gt;values&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
  &lt;span class="n"&gt;valuePointers&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="n"&gt;i&lt;/span&gt;&lt;span class="p"&gt;]&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;values&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="n"&gt;i&lt;/span&gt;&lt;span class="p"&gt;]&lt;/span&gt;
 &lt;span class="p"&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;


&lt;p&gt;So, we are ready to fetch data in a new way and it’s time to serialize this data.&lt;br&gt;
The JSON library is heavy, but we can make serialization easier.&lt;/p&gt;

&lt;p&gt;Columns are simple token-level data usually — we can turn them into JSON strings, then we will just escape special symbols by our escape function -&lt;br&gt;
&lt;/p&gt;
&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="n"&gt;escape&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;in&lt;/span&gt; &lt;span class="p"&gt;[]&lt;/span&gt;&lt;span class="kt"&gt;byte&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;[]&lt;/span&gt;&lt;span class="kt"&gt;byte&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
 &lt;span class="k"&gt;var&lt;/span&gt; &lt;span class="n"&gt;out&lt;/span&gt; &lt;span class="n"&gt;bytes&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Buffer&lt;/span&gt;
 &lt;span class="k"&gt;for&lt;/span&gt; &lt;span class="n"&gt;_&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;b&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="k"&gt;range&lt;/span&gt; &lt;span class="n"&gt;in&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
  &lt;span class="k"&gt;switch&lt;/span&gt; &lt;span class="n"&gt;b&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
  &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="sc"&gt;'\n'&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="sc"&gt;'\r'&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="sc"&gt;'\t'&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="sc"&gt;'\b'&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="sc"&gt;'\f'&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="sc"&gt;'\\'&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="sc"&gt;'"'&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
   &lt;span class="n"&gt;out&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteByte&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="sc"&gt;'\\'&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
   &lt;span class="n"&gt;out&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteByte&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;b&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
  &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="sc"&gt;'/'&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
   &lt;span class="n"&gt;out&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteByte&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="sc"&gt;'\\'&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
   &lt;span class="n"&gt;out&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteByte&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;b&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
  &lt;span class="k"&gt;default&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
   &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;b&lt;/span&gt; &lt;span class="o"&gt;&amp;lt;&lt;/span&gt; &lt;span class="m"&gt;32&lt;/span&gt; &lt;span class="o"&gt;||&lt;/span&gt; &lt;span class="n"&gt;b&lt;/span&gt; &lt;span class="o"&gt;==&lt;/span&gt; &lt;span class="m"&gt;127&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;out&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteString&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;`\u00`&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="n"&gt;out&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteString&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;strconv&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;FormatInt&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="kt"&gt;int64&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;b&lt;/span&gt;&lt;span class="p"&gt;),&lt;/span&gt; &lt;span class="m"&gt;16&lt;/span&gt;&lt;span class="p"&gt;))&lt;/span&gt;
   &lt;span class="p"&gt;}&lt;/span&gt; &lt;span class="k"&gt;else&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;out&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteByte&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;b&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
   &lt;span class="p"&gt;}&lt;/span&gt;
  &lt;span class="p"&gt;}&lt;/span&gt;
 &lt;span class="p"&gt;}&lt;/span&gt;
 &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;out&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Bytes&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;


&lt;p&gt;Now let’s think about data types. We can determine the type of column (using sql ColumnType structure sql.ColumnType)&lt;br&gt;
&lt;/p&gt;
&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="n"&gt;isDigit&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;c&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;sql&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ColumnType&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="kt"&gt;bool&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
 &lt;span class="k"&gt;switch&lt;/span&gt; &lt;span class="n"&gt;c&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;DatabaseTypeName&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"TINYINT"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"SMALLINT"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"MEDIUMINT"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"BIGINT"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"INT"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"INT1"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"INT2"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"INT3"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"INT4"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"INT8"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"BOOL"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"BOOLEAN"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"DECIMAL"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"DEC"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"NUMERIC"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"FIXED"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"NUMBER"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"FLOAT"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;case&lt;/span&gt; &lt;span class="s"&gt;"DOUBLE"&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
 &lt;span class="k"&gt;default&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;false&lt;/span&gt;
 &lt;span class="p"&gt;}&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;


&lt;p&gt;And finally, let’s apply primitive serialization:&lt;br&gt;
&lt;/p&gt;
&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="n"&gt;Row2Json&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;columns&lt;/span&gt; &lt;span class="p"&gt;[]&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;sql&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ColumnType&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;values&lt;/span&gt; &lt;span class="p"&gt;[]&lt;/span&gt;&lt;span class="n"&gt;sql&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;RawBytes&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="kt"&gt;string&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="kt"&gt;error&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
 &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="nb"&gt;len&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;values&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="o"&gt;==&lt;/span&gt; &lt;span class="m"&gt;0&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="s"&gt;""&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;errors&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;New&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"no data in values"&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
 &lt;span class="p"&gt;}&lt;/span&gt;
 &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="nb"&gt;len&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;columns&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="nb"&gt;len&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;values&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
  &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="s"&gt;""&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;errors&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;New&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"columns and values length not equal"&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
 &lt;span class="p"&gt;}&lt;/span&gt;
 &lt;span class="k"&gt;var&lt;/span&gt; &lt;span class="n"&gt;buff&lt;/span&gt; &lt;span class="n"&gt;strings&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Builder&lt;/span&gt;
 &lt;span class="n"&gt;buff&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteByte&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="sc"&gt;'{'&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
 &lt;span class="k"&gt;for&lt;/span&gt; &lt;span class="n"&gt;i&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;val&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="k"&gt;range&lt;/span&gt; &lt;span class="n"&gt;values&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
  &lt;span class="n"&gt;buff&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteByte&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="sc"&gt;'"'&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
  &lt;span class="n"&gt;buff&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteString&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;columns&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="n"&gt;i&lt;/span&gt;&lt;span class="p"&gt;]&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Name&lt;/span&gt;&lt;span class="p"&gt;())&lt;/span&gt;
  &lt;span class="n"&gt;buff&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteByte&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="sc"&gt;'"'&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
  &lt;span class="n"&gt;buff&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteByte&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="sc"&gt;':'&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
  &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="nb"&gt;len&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;val&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="o"&gt;&amp;gt;&lt;/span&gt; &lt;span class="m"&gt;0&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
   &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="o"&gt;!&lt;/span&gt;&lt;span class="n"&gt;isDigit&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;columns&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="n"&gt;i&lt;/span&gt;&lt;span class="p"&gt;])&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;buff&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteByte&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="sc"&gt;'"'&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
   &lt;span class="p"&gt;}&lt;/span&gt;
   &lt;span class="n"&gt;buff&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Write&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;escape&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;val&lt;/span&gt;&lt;span class="p"&gt;))&lt;/span&gt;
   &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="o"&gt;!&lt;/span&gt;&lt;span class="n"&gt;isDigit&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;columns&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="n"&gt;i&lt;/span&gt;&lt;span class="p"&gt;])&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;buff&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteByte&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="sc"&gt;'"'&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
   &lt;span class="p"&gt;}&lt;/span&gt;
  &lt;span class="p"&gt;}&lt;/span&gt; &lt;span class="k"&gt;else&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
   &lt;span class="n"&gt;buff&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteString&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"null"&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
  &lt;span class="p"&gt;}&lt;/span&gt;
  &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;i&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="nb"&gt;len&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;values&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;&lt;span class="o"&gt;-&lt;/span&gt;&lt;span class="m"&gt;1&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
   &lt;span class="n"&gt;buff&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteByte&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="sc"&gt;','&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
  &lt;span class="p"&gt;}&lt;/span&gt;
 &lt;span class="p"&gt;}&lt;/span&gt;
 &lt;span class="n"&gt;buff&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteByte&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="sc"&gt;'}'&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;

 &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;buff&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;String&lt;/span&gt;&lt;span class="p"&gt;(),&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;


&lt;p&gt;Benchmark:&lt;br&gt;
&lt;code&gt;cpu: 11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz&lt;br&gt;
BenchmarkRow2Json&lt;br&gt;
BenchmarkRow2Json-8     2881545        385.3 ns/op      440 B/op        9 allocs/op&lt;/code&gt;&lt;/p&gt;
&lt;h3&gt;
  
  
  Use UNIX way to output
&lt;/h3&gt;

&lt;p&gt;We will use UNIX way of output of our program — i.e. we will not create an output slice — we will out data into standard output stream instead — then we can use the output as a standard pipe in UNIX:&lt;br&gt;
&lt;/p&gt;
&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="c"&gt;// create new buffer&lt;/span&gt;
 &lt;span class="n"&gt;writer&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;bufio&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;NewWriter&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;os&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Stdout&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
 &lt;span class="k"&gt;defer&lt;/span&gt; &lt;span class="n"&gt;writer&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Flush&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;

 &lt;span class="n"&gt;writer&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteByte&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="sc"&gt;'['&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="c"&gt;//start print array of data&lt;/span&gt;
 &lt;span class="o"&gt;...&lt;/span&gt;
 &lt;span class="n"&gt;msg&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;errMsg&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;dbf&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Row2Json&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;columns&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;values&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
 &lt;span class="o"&gt;...&lt;/span&gt;
 &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;_&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;writer&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteString&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;msg&lt;/span&gt;&lt;span class="p"&gt;);&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
   &lt;span class="n"&gt;log&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Fatalf&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"fault write row: %v"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
  &lt;span class="p"&gt;}&lt;/span&gt; &lt;span class="c"&gt;// write serialized row&lt;/span&gt;
 &lt;span class="o"&gt;...&lt;/span&gt;
 &lt;span class="n"&gt;writer&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteByte&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="sc"&gt;']'&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="c"&gt;// finish serialized slice&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;


&lt;p&gt;In success execution we will get something like:&lt;br&gt;
&lt;/p&gt;
&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight shell"&gt;&lt;code&gt;%  ./db2json_ds 3 2&amp;gt;/dev/null | jq
&lt;span class="o"&gt;[&lt;/span&gt;
  &lt;span class="o"&gt;{&lt;/span&gt;
    &lt;span class="s2"&gt;"id"&lt;/span&gt;: 1,
    &lt;span class="s2"&gt;"product"&lt;/span&gt;: &lt;span class="s2"&gt;"product_1"&lt;/span&gt;,
    &lt;span class="s2"&gt;"description"&lt;/span&gt;: null,
    &lt;span class="s2"&gt;"price"&lt;/span&gt;: 1.23,
    &lt;span class="s2"&gt;"qty"&lt;/span&gt;: 10,
    &lt;span class="s2"&gt;"date"&lt;/span&gt;: &lt;span class="s2"&gt;"2021-01-01 00:00:00"&lt;/span&gt;
  &lt;span class="o"&gt;}&lt;/span&gt;,
  &lt;span class="o"&gt;{&lt;/span&gt;
    &lt;span class="s2"&gt;"id"&lt;/span&gt;: 2,
    &lt;span class="s2"&gt;"product"&lt;/span&gt;: &lt;span class="s2"&gt;"product_2"&lt;/span&gt;,
    &lt;span class="s2"&gt;"description"&lt;/span&gt;: null,
    &lt;span class="s2"&gt;"price"&lt;/span&gt;: 2.23,
    &lt;span class="s2"&gt;"qty"&lt;/span&gt;: 20,
    &lt;span class="s2"&gt;"date"&lt;/span&gt;: &lt;span class="s2"&gt;"2021-01-01 00:00:00"&lt;/span&gt;
  &lt;span class="o"&gt;}&lt;/span&gt;,
  &lt;span class="o"&gt;{&lt;/span&gt;
    &lt;span class="s2"&gt;"id"&lt;/span&gt;: 3,
    &lt;span class="s2"&gt;"product"&lt;/span&gt;: &lt;span class="s2"&gt;"product_3"&lt;/span&gt;,
    &lt;span class="s2"&gt;"description"&lt;/span&gt;: null,
    &lt;span class="s2"&gt;"price"&lt;/span&gt;: 3.23,
    &lt;span class="s2"&gt;"qty"&lt;/span&gt;: 30,
    &lt;span class="s2"&gt;"date"&lt;/span&gt;: &lt;span class="s2"&gt;"2021-01-01 00:00:00"&lt;/span&gt;
  &lt;span class="o"&gt;}&lt;/span&gt;
&lt;span class="o"&gt;]&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;


&lt;p&gt;It’s a time of the moment of truth — fetch 10 million records:&lt;/p&gt;

&lt;p&gt;&lt;code&gt;% ./db2json_ds 10000000 1&amp;gt;/dev/null                                                                                                                              &lt;br&gt;
Elapsed time: 11894 ms, HeapAlloc = 2.436 MB, Sys = 11.710 MB&lt;br&gt;
10000000 records read&lt;/code&gt;&lt;br&gt;
Let’s compare with the starting point:&lt;/p&gt;

&lt;ul&gt;
&lt;li&gt;Execution time — 11.647 seconds instead 12.631 seconds;&lt;/li&gt;
&lt;li&gt;Memory consumption — 11.710 MB instead 7099.447 MB.
So, up to 10 percent faster and 600 times less memory consumption.&lt;/li&gt;
&lt;/ul&gt;
&lt;h2&gt;
  
  
  Conclusion
&lt;/h2&gt;

&lt;p&gt;Let’s examine the broader scope of the tests.&lt;br&gt;
Test comparison table (the length of result json file is 1.2Gb)&lt;br&gt;
&lt;/p&gt;
&lt;div class="ltag_gist-liquid-tag"&gt;
  
&lt;/div&gt;



&lt;p&gt;Benchmarks comparison table:&lt;br&gt;
&lt;/p&gt;
&lt;div class="ltag_gist-liquid-tag"&gt;
  
&lt;/div&gt;


&lt;p&gt;Real test memory consumption comparison table:&lt;br&gt;
&lt;/p&gt;
&lt;div class="ltag_gist-liquid-tag"&gt;
  
&lt;/div&gt;


&lt;p&gt;The fast method (fetch data using slices) is not the fastest in benchmarks, but it’s fastest and the least gluttonous in real tests.&lt;/p&gt;

&lt;p&gt;Analyzing the results, we can make two important conclusions, in my opinion :&lt;/p&gt;

&lt;ul&gt;
&lt;li&gt;simple solutions always work more effectively;&lt;/li&gt;
&lt;li&gt;real tests are always more important than synthetic ones.&lt;/li&gt;
&lt;/ul&gt;

&lt;p&gt;Happy coding 🙂&lt;/p&gt;

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