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extstats: change output functions to emit valid JSON

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Manipulating extended statistics is more convenient as JSON than the
current ad-hoc format, so let's change before it's too late.

Discussion: https://postgr.es/m/20170420193828.k3fliiock5hdnehn@alvherre.pgsql
This commit is contained in:
Alvaro Herrera
2017-05-02 18:49:32 -03:00
parent e950024066
commit 93bbeec6a2
4 changed files with 28 additions and 33 deletions
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11
doc/src/sgml/perform.sgml
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@ -1138,9 +1138,9 @@ ANALYZE zipcodes;
SELECT stxname, stxkeys, stxdependencies
FROM pg_statistic_ext
WHERE stxname = 'stts';
stxname | stxkeys | stxdependencies
---------+---------+--------------------------------------------
stts | 1 5 | [{1 => 5 : 1.000000}, {5 => 1 : 0.423130}]
stxname | stxkeys | stxdependencies
---------+---------+------------------------------------------
stts | 1 5 | {"1 => 5": 1.000000, "5 => 1": 0.423130}
(1 row)
</programlisting>
where it can be seen that column 1 (a zip code) fully determines column
@ -1225,10 +1225,9 @@ ANALYZE zipcodes;
SELECT stxkeys AS k, stxndistinct AS nd
FROM pg_statistic_ext
WHERE stxname = 'stts2';
-[ RECORD 1 ]---------------------------------------------
-[ RECORD 1 ]--------------------------------------------------------
k | 1 2 5
nd | [{(b 1 2), 33178.000000}, {(b 1 5), 33178.000000},
{(b 2 5), 27435.000000}, {(b 1 2 5), 33178.000000}]
nd | {"1, 2": 33178, "1, 5": 33178, "2, 5": 27435, "1, 2, 5": 33178}
(1 row)
</programlisting>
which indicates that there are three combinations of columns that