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[DOCS] Minor copy edits and typo fixes

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Change-Id: I353a7917eb770aa40696476a587d7600289c336c
Cherry-picks: not for 2.x.
Reviewed-on: http://gerrit.cloudera.org:8080/10276
Reviewed-by: Alex Rodoni <arodoni@cloudera.com>
Tested-by: Alex Rodoni <arodoni@cloudera.com>
This commit is contained in:
Alex Rodoni
2018-05-01 15:07:30 -07:00
parent 52a2d90f98
commit 80d07afff3
1 changed files with 78 additions and 88 deletions
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166
docs/topics/impala_decimal.xml
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@@ -208,20 +208,20 @@ under the License.
</p>
<p>
For all arithmetic options, the resulting precision is at most 38.
For all arithmetic operations, the resulting precision is at most 38.
</p>
<p>
If the precision of the result would be greater than 38, Impala truncates the result from
the back, but keeps at least 6 fractional digits in scale and rounds.
If the resulting precision would be greater than 38, Impala truncates the result from the
back, but keeps at least 6 fractional digits in scale and rounds.
</p>
<p>
For example, <codeph>DECIMAL(38, 20) * DECIMAL(38, 20)</codeph> returns
<codeph>DECIMAL(38, 6)</codeph>. According to the table below, the resulting precision and
scale would be <codeph>(77, 40)</codeph>, but they are higher than the maximum precision
and scale. So, Impala sets the precision to the maximum allowed 38, and truncates the
scale to 6.
and scale for <codeph>DECIMAL</codeph>. So, Impala sets the precision to the maximum
allowed 38, and truncates the scale to 6.
</p>
<p>
@@ -401,8 +401,7 @@ INSERT INTO flt SELECT CAST(1e37 AS DECIMAL(38, 0));
SELECT CAST(c AS DECIMAL(38, 0)) FROM flt;
Result: 9999999933815812510711506376257961984</codeblock>
<p
dir="ltr">
<p dir="ltr">
The result has a loss of information due to implicit casting. This is why we
discourage using the <codeph>DOUBLE</codeph> and <codeph>FLOAT</codeph> types in
general.
@@ -426,7 +425,7 @@ Result: 9999999933815812510711506376257961984</codeblock>
<li>
Integer values can be implicitly converted to <codeph>DECIMAL</codeph> when there is
enough room in the <codeph>DECIMAL</codeph> to guarantee that all digits will fit. The
enough room in the <codeph>DECIMAL</codeph> to guarantee that all digits fit. The
integer types require the following numbers of digits to the left of the decimal point
when converted to <codeph>DECIMAL</codeph>:
<ul>
@@ -594,11 +593,8 @@ INSERT INTO decimals_11_8 VALUES (CAST(1 AS TINYINT));</codeblock>
<ul>
<li dir="ltr">
<p dir="ltr">
If scale in <codeph>STRING</codeph> > scale in <codeph>DECIMAL</codeph>:
</p>
<p dir="ltr">
The fractional digits are rounded to the <codeph>DECIMAL</codeph> scale.
If scale in <codeph>STRING</codeph> > scale in <codeph>DECIMAL</codeph>, the
fractional digits are rounded to the <codeph>DECIMAL</codeph> scale.
</p>
<p dir="ltr">
@@ -724,15 +720,10 @@ INSERT INTO decimals_11_8 VALUES (CAST(1 AS TINYINT));</codeblock>
<p conref="../shared/impala_common.xml#common/file_format_blurb"/>
<p>
<p dir="ltr">
The <codeph>DECIMAL</codeph> data type can be stored in any of the file formats supported
by Impala.
<ul>
<li dir="ltr">
<p dir="ltr">
The <codeph>DECIMAL</codeph> data type can be stored in any of the file formats
supported by Impala.
</p>
</li>
<li dir="ltr">
<p dir="ltr">
Impala can query Avro, RCFile, or SequenceFile tables that contain
@@ -834,10 +825,10 @@ INSERT INTO decimals_11_8 VALUES (CAST(1 AS TINYINT));</codeblock>
Although an <codeph>ALTER TABLE ... REPLACE COLUMNS</codeph> statement that
changes the precision or scale of a <codeph>DECIMAL</codeph> column succeeds,
any subsequent attempt to query the changed column results in a fatal error.
(The other columns can still be queried successfully.) This is because the
metadata about the columns is stored in the data files themselves, and
<codeph>ALTER TABLE</codeph> does not actually make any updates to the data
files.
This is because the metadata about the columns is stored in the data files
themselves, and <codeph>ALTER TABLE</codeph> does not actually make any updates
to the data files. The other unaltered columns can still be queried
successfully.
</p>
</li>
@@ -870,102 +861,101 @@ INSERT INTO decimals_11_8 VALUES (CAST(1 AS TINYINT));</codeblock>
STATS</codeph> statement.
</p>
<p conref="../shared/impala_common.xml#common/compatibility_blurb"/>
<p>
<b>Compatibility with older version of DECIMAL:</b>
</p>
<p>
<ul>
<li dir="ltr">
<p dir="ltr">
This version of <codeph>DECIMAL</codeph> type is the default in
<keyword keyref="impala30_full"/> and higher. The key differences between this
version of <codeph>DECIMAL</codeph> and the previous <codeph>DECIMAL</codeph> V1 in
Impala 2.x include the following.
</p>
<simpletable frame="all" relcolwidth="1* 1* 1*"
id="simpletable_bdr_rzc_qdb">
This version of <codeph>DECIMAL</codeph> type is the default in
<keyword
keyref="impala30_full"/> and higher. The key differences between this
version of <codeph>DECIMAL</codeph> and the previous <codeph>DECIMAL</codeph> V1 in Impala
2.x include the following.
</p>
<sthead>
<p>
<simpletable frame="all" relcolwidth="1* 1* 1*"
id="simpletable_bwl_khm_rdb">
<stentry/>
<sthead>
<stentry>DECIMAL in <keyword keyref="impala30_full"/> or
higher</stentry>
<stentry/>
<stentry>DECIMAL in <keyword keyref="impala212_full"/> or
lower
<stentry>DECIMAL in <keyword keyref="impala30_full"/> or
higher</stentry>
</stentry>
<stentry>DECIMAL in <keyword keyref="impala212_full"/> or lower
</stentry>
</sthead>
</sthead>
<strow>
<strow>
<stentry>Overall behavior</stentry>
<stentry>Overall behavior</stentry>
<stentry>Returns either the result or an error.</stentry>
<stentry>Returns either the result or an error.</stentry>
<stentry>Returns either the result or <codeph>NULL</codeph> with a
warning.</stentry>
<stentry>Returns either the result or <codeph>NULL</codeph> with a
warning.</stentry>
</strow>
</strow>
<strow>
<strow>
<stentry>Overflow behavior</stentry>
<stentry>Overflow behavior</stentry>
<stentry>Aborts with an error.</stentry>
<stentry>Aborts with an error.</stentry>
<stentry>Issues a warning and returns
<codeph>NULL</codeph>.</stentry>
<stentry>Issues a warning and returns <codeph>NULL</codeph>.</stentry>
</strow>
</strow>
<strow>
<strow>
<stentry>Truncation / rounding behavior in arithmetic</stentry>
<stentry>Truncation / rounding behavior in arithmetic</stentry>
<stentry>Truncates and rounds digits from the back.</stentry>
<stentry>Truncates and rounds digits from the back.</stentry>
<stentry>Truncates digits from the front.</stentry>
<stentry>Truncates digits from the front.</stentry>
</strow>
</strow>
<strow>
<strow>
<stentry>String cast</stentry>
<stentry>String cast</stentry>
<stentry>Truncates from the back and rounds.</stentry>
<stentry>Truncates from the back and rounds.</stentry>
<stentry>Truncates from the back.</stentry>
<stentry>Truncates from the back.</stentry>
</strow>
</strow>
</simpletable>
<p>
If you need to continue using the first version of the <codeph>DECIMAL</codeph> type
for the backward compatibility of your queries, set the <codeph>DECIMAL_V2</codeph>
query option to <codeph>FALSE</codeph>:
</simpletable>
</p>
<p>
If you need to continue using the first version of the <codeph>DECIMAL</codeph> type for
the backward compatibility of your queries, set the <codeph>DECIMAL_V2</codeph> query
option to <codeph>FALSE</codeph>:
<codeblock>SET DECIMAL_V2=FALSE;</codeblock>
</p>
</li>
</p>
<li dir="ltr">
<p dir="ltr">
Use the <codeph>DECIMAL</codeph> data type in Impala for applications where you used
the <codeph>NUMBER</codeph> data type in Oracle.
</p>
<p>
<b>Compatibility with other databases:</b>
</p>
<p dir="ltr">
The Impala <codeph>DECIMAL</codeph> type does not support the Oracle idioms of
<codeph>*</codeph> for scale.
</p>
<p dir="ltr">
Use the <codeph>DECIMAL</codeph> data type in Impala for applications where you used the
<codeph>NUMBER</codeph> data type in Oracle.
</p>
<p dir="ltr">
The Impala <codeph>DECIMAL</codeph> type does not support negative values for
precision.
</p>
</li>
</ul>
<p dir="ltr">
The Impala <codeph>DECIMAL</codeph> type does not support the Oracle idioms of
<codeph>*</codeph> for scale.
</p>
<p dir="ltr">
The Impala <codeph>DECIMAL</codeph> type does not support negative values for precision.
</p>
</conbody>