Updated README - added section for index storage space

Author: MartinMikita

README.md

@@ -19,7 +19,8 @@ This endpoint returns 20 results matching the `<query>` within a specific countr
 
 # Input data.tsv format
 
-This service accepts only TSV file named `data.tsv` with the specific order of columns:
+This service accepts only TSV file named `data.tsv` (or gzip-ed version named `data.tsv.gz`)
+ with the specific order of columns:
 
 ```
 name
@@ -47,6 +48,7 @@ wikidata
 wikipedia
 ```
 
+The source data should be **sorted by the column `importance`**.
 For the description of these columns, see [data format in geometalab/OSMNames repository](https://github.com/geometalab/OSMNames#data-format-of-tsv-export-of-osmnames).
 
 
@@ -56,24 +58,24 @@ This docker image consists from internaly connected and setup OSMNames Websearch
 
 Whole service can be run from command-line with one command:
 
-Run with demo data (10 lines) only
+Run with demo data (sample of 100k lines from [geometalab/OSMNames](https://github.com/OSMNames/OSMNames/releases/tag/v1.1)) only
 
 ```
 docker run -d --name klokantech-osmnames-sphinxsearch -p 80:80 klokantech/osmnames-sphinxsearch
 ```
 
-You can attach your file `data.tsv`, which has to be located in the internal path `/data/input/data.tsv`:
+You can attach your file `data.tsv` (or `data.tsv.gz`), which has to be located in the internal path `/data/input/data.tsv` (or `/data/input/data.tsv.gz`):
 
 ```
 docker run -d --name klokantech-osmnames-sphinxsearch \
-    -v /path/to/folder/data.tsv:/data/input/ \
+    -v /path/to/folder/:/data/input/ \
     -p 80:80 \
     klokantech/osmnames-sphinxsearch
 ```
 
 This file will be indexed on the first run or if index files are missing.
 
-You can specify path for index folder as well:
+You can specify a path for index folder as well:
 
 ```
 docker run -d --name klokantech-osmnames-sphinxsearch \
@@ -88,7 +90,7 @@ You can attach your path with the following folder structure:
 ```
 /path/to/folder/
     - input/
-        - data.tsv
+        - data.tsv (or data.tsv.gz)
     - index/
 ```
 
@@ -97,3 +99,15 @@ directly with simple command:
 ```
 docker run -d -v /path/to/folder/:/data/ -p 80:80 klokantech/osmnames-sphinxsearch
 ```
+
+# Index storage space
+
+The service for full-text search SphinxSearch requires indexing a source data.
+The index operation is required only for the first time or if source data has been changed.
+This operation takes longer on a source with more lines, and requires more space storage as well.
+
+A demo sample data with 100 000 lines has **9.3 MiB gzip**-ed source data file and requires storage space of **133.8 MiB for the index** folder. The operation tooks in an average 15 seconds.
+
+The [full planet source data](https://github.com/OSMNames/OSMNames/releases/download/v1.1/planet-latest.tsv.gz) with 21 million lines requires storage space of **27.4 GiB for the index** folder. The operation tooks in an average 48 minutes.
+
+The index operation is done automatically if certain the index file is missing via the prepared script `sphinx-reindex.sh`. You can use this script to force index operation as well: `$ time bash sphinx-reindex.sh force`.