arina-ielchiieva commented on a change in pull request #1850: DRILL-7168:
Implement ALTER SCHEMA ADD / REMOVE commands
URL: https://github.com/apache/drill/pull/1850#discussion_r322683341
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File path: exec/java-exec/src/main/codegen/includes/parserImpls.ftl
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@@ -534,6 +534,110 @@ SqlNode SqlDescribeSchema() :
)
}
+/**
+* Parses ALTER SCHEMA statements:
+*
+* ALTER SCHEMA
+* (FOR TABLE dfs.tmp.nation | PATH '/tmp/schema.json')
+* ADD [OR REPLACE]
+* [COLUMNS (col1 int, col2 varchar)]
+* [PROPERTIES ('prop1'='val1', 'prop2'='val2')]
+*
+* ALTER SCHEMA
+* (FOR TABLE dfs.tmp.nation | PATH '/tmp/schema.json')
+* REMOVE
+* [COLUMNS (`col1`, `col2`)]
+* [PROPERTIES ('prop1', 'prop2')]
+*/
+SqlNode SqlAlterSchema() :
+{
+ SqlParserPos pos;
+ SqlIdentifier table = null;
+ SqlNode path = null;
+}
+{
+ <ALTER> { pos = getPos(); }
+ <SCHEMA>
+ (
+ <FOR> <TABLE> { table = CompoundIdentifier(); }
+ |
+ <PATH> { path = StringLiteral(); }
+ )
+ (
+ <ADD> { return SqlAlterSchemaAdd(pos, table, path); }
+ |
+ <REMOVE> { return SqlAlterSchemaRemove(pos, table, path); }
+ )
+}
+
+SqlNode SqlAlterSchemaAdd(SqlParserPos pos, SqlIdentifier table, SqlNode path)
:
+{
+ boolean replace = false;
+ SqlCharStringLiteral schema = null;
+ SqlNodeList properties = null;
+}
+{
+ [ <OR> <REPLACE> { replace = true; } ]
+ [ <COLUMNS> { schema = ParseSchema(); } ]
+ [
+ <PROPERTIES> <LPAREN>
+ {
+ properties = new SqlNodeList(getPos());
+ addProperty(properties);
+ }
+ (
+ <COMMA> { addProperty(properties); }
+ )*
+ <RPAREN>
+ ]
+ {
+ if (schema == null && properties == null) {
+ throw new ParseException("ALTER SCHEMA ADD command must have at
least <COLUMNS> or <PROPERTIES> keyword indicated.");
+ }
+ return new SqlSchema.Add(pos, table, path,
SqlLiteral.createBoolean(replace, getPos()), schema, properties);
+ }
+}
+
+SqlCharStringLiteral ParseSchema() :
Review comment:
No, all because of context switch, for create schema we use load and
paren_string where each returns some specific result and one of push returns to
default context. For alter schema add we use only paren_string and only this
one can return to default context. The reason it is factored out into separate
method is to prevent lookahead. Since first we need context switch and only
then token search. With this method inline lookahead was happening before
context switch and token from different context was never found.
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