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parser/parser.y: S/R conflicts 25->24. #87

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parser/parser.y: S/R conflicts 25->24. #87

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16 changes: 13 additions & 3 deletions parser/parser.y
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Original file line number Diff line number Diff line change
Expand Up @@ -274,10 +274,11 @@ import (
CharsetName "Charset Name"
CollationName "Collation Name"
ColumnDef "table column definition"
ColumnKeywordOpt "Column keyword or empty"
ColumnName "column name"
ColumnNameList "column name list"
ColumnNameListOpt "column name list opt"
ColumnKeywordOpt "Column keyword or empty"
ColumnOptColumnName "optional COLUMN and column name"
ColumnSetValue "insert statement set value by column name"
ColumnSetValueList "insert statement set value by column name list"
CommaOpt "optional comma"
Expand Down Expand Up @@ -531,11 +532,11 @@ AlterSpecification:
Constraint: constraint,
}
}
| "DROP" ColumnKeywordOpt ColumnName
| "DROP" ColumnOptColumnName
{
$$ = &ddl.AlterSpecification{
Action: ddl.AlterDropColumn,
Name: $3.(string),
Name: $2.(string),
}
}
| "DROP" "PRIMARY" "KEY"
Expand All @@ -560,6 +561,15 @@ AlterSpecification:
KeyOrIndex:
"KEY"|"INDEX"

ColumnOptColumnName:
"COLUMN"
| "COLUMN" "COLUMN"
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here may be a valid syntax, for drop column column or above drop column ?

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AFAICT, the original grammar (before this PR) would have accepted the sentence drop column column as a valid AlterSpecification. The first column instance is the optional unreserved column keyword, the second column instance is an Identifier and the real name of the column to drop.

That's the mess created by the keyword/identifiers mixing.

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"Alter table t drop column int;" is a valid sql statement but "int" is not an identifier in parser.y. @cznic
"Alter table t drop column column;" is also a valid sql statement. @siddontang

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In this way I reduce S/R conflict from 25 to 24. Is this a better way? @cznic
diff --git a/parser/parser.y b/parser/parser.y
index 8b70e02..96b6586 100644
--- a/parser/parser.y
+++ b/parser/parser.y
@@ -531,7 +531,14 @@ AlterSpecification:
Constraint: constraint,
}
}
-| "DROP" ColumnKeywordOpt ColumnName
+| "DROP" ColumnName

  •   {

  •           $$ = &ddl.AlterSpecification{

  •                   Action: ddl.AlterDropColumn,

  •                   Name: $2.(string),

  •           }

  •   }
    +| "DROP" "COLUMN" ColumnName
    {
    $$ = &ddl.AlterSpecification{
    Action: ddl.AlterDropColumn,

| "COLUMN" identifier
{
$$ = $2
}
| identifier

ColumnKeywordOpt:
{}
| "COLUMN"
Expand Down