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Commit716ea62

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Make construct_[md_]array return a valid empty array for zero-size input.
If construct_array() or construct_md_array() were given a dimension ofzero, they'd produce an array that contains no elements but has positivedimension. This violates a general expectation that empty arrays shouldhave ndims = 0; in particular, while arrays like this print as empty,they don't compare equal to other empty arrays.Up to now we've expected callers to avoid making such calls and insteadbe careful to call construct_empty_array() if there would be no elements.But this has always been an easily missed case, and we've repeatedly had tofix callers to do it right. In bug #14826, Erwin Brandstetter pointed outyet another such oversight, in ts_lexize(); and a bit of examination ofother call sites found at least two more with similar issues. So let'sfix the problem centrally and permanently by changing these two functionsto construct a proper zero-D empty array whenever the array would be empty.This renders a few explicit calls of construct_empty_array() redundant,but the only such place I found that really seemed worth changing was inExecEvalArrayExpr().Although this fixes some very old bugs, no back-patch: the problem ispretty minor and the risk of changing behavior seems to outweigh thebenefit in stable branches.Discussion:https://postgr.es/m/20170923125723.1448.39412@wrigleys.postgresql.orgDiscussion:https://postgr.es/m/20570.1506198383@sss.pgh.pa.us
1 parentf2ab389 commit716ea62

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4 files changed

+21
-12
lines changed

4 files changed

+21
-12
lines changed

‎src/backend/executor/execExprInterp.c

Lines changed: 0 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -2131,14 +2131,6 @@ ExecEvalArrayExpr(ExprState *state, ExprEvalStep *op)
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Datum*dvalues=op->d.arrayexpr.elemvalues;
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bool*dnulls=op->d.arrayexpr.elemnulls;
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2134-
/* Shouldn't happen here, but if length is 0, return empty array */
2135-
if (nelems==0)
2136-
{
2137-
*op->resvalue=
2138-
PointerGetDatum(construct_empty_array(element_type));
2139-
return;
2140-
}
2141-
21422134
/* setup for 1-D array of the given length */
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ndims=1;
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dims[0]=nelems;

‎src/backend/utils/adt/arrayfuncs.c

Lines changed: 6 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -3297,6 +3297,7 @@ array_map(FunctionCallInfo fcinfo, Oid retType, ArrayMapState *amstate)
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*
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* A palloc'd 1-D array object is constructed and returned. Note that
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* elem values will be copied into the object even if pass-by-ref type.
3300+
* Also note the result will be 0-D not 1-D if nelems = 0.
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*
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* NOTE: it would be cleaner to look up the elmlen/elmbval/elmalign info
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* from the system catalogs, given the elmtype. However, the caller is
@@ -3331,6 +3332,7 @@ construct_array(Datum *elems, int nelems,
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*
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* A palloc'd ndims-D array object is constructed and returned. Note that
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* elem values will be copied into the object even if pass-by-ref type.
3335+
* Also note the result will be 0-D not ndims-D if any dims[i] = 0.
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*
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* NOTE: it would be cleaner to look up the elmlen/elmbval/elmalign info
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* from the system catalogs, given the elmtype. However, the caller is
@@ -3362,12 +3364,12 @@ construct_md_array(Datum *elems,
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errmsg("number of array dimensions (%d) exceeds the maximum allowed (%d)",
33633365
ndims,MAXDIM)));
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3365-
/* fast track for empty array */
3366-
if (ndims==0)
3367-
returnconstruct_empty_array(elmtype);
3368-
33693367
nelems=ArrayGetNItems(ndims,dims);
33703368

3369+
/* if ndims <= 0 or any dims[i] == 0, return empty array */
3370+
if (nelems <=0)
3371+
returnconstruct_empty_array(elmtype);
3372+
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/* compute required space */
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nbytes=0;
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hasnulls= false;

‎src/test/regress/expected/tsearch.out

Lines changed: 11 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -618,6 +618,17 @@ SELECT * from ts_debug('english', '5aew.werc.ewr:8100/?xx');
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url_path | URL path | /?xx | {simple} | simple | {/?xx}
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(3 rows)
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621+
SELECT token, alias,
622+
dictionaries, dictionaries is null as dnull, array_dims(dictionaries) as ddims,
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lexemes, lexemes is null as lnull, array_dims(lexemes) as ldims
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from ts_debug('english', 'a title');
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token | alias | dictionaries | dnull | ddims | lexemes | lnull | ldims
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-------+-----------+----------------+-------+-------+---------+-------+-------
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a | asciiword | {english_stem} | f | [1:1] | {} | f |
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| blank | {} | f | | | t |
629+
title | asciiword | {english_stem} | f | [1:1] | {titl} | f | [1:1]
630+
(3 rows)
631+
621632
-- to_tsquery
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SELECT to_tsquery('english', 'qwe & sKies ');
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to_tsquery

‎src/test/regress/sql/tsearch.sql

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -145,6 +145,10 @@ SELECT * from ts_debug('english', 'http://www.harewoodsolutions.co.uk/press.aspx
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SELECT*from ts_debug('english','http://aew.wer0c.ewr/id?ad=qwe&dw<span>');
146146
SELECT*from ts_debug('english','http://5aew.werc.ewr:8100/?');
147147
SELECT*from ts_debug('english','5aew.werc.ewr:8100/?xx');
148+
SELECT token, alias,
149+
dictionaries, dictionaries isnullas dnull, array_dims(dictionaries)as ddims,
150+
lexemes, lexemes isnullas lnull, array_dims(lexemes)as ldims
151+
from ts_debug('english','a title');
148152

149153
-- to_tsquery
150154

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