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jdbc: support for sub-set of JDBC escape syntax
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Add a driver SQL pre-processing before sending it to the server. The
driver supports sub-set of scalar functions defined by the spec
(appendix C), outer joins, escape clause for SQL LIKE operator, and
limit/offset clause. The processed result can be received using
Connection.nativeSQL() method.

Closes #79
Closes #76
Closes #81
Closes #83
Closes #84
Affects: #108
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@nicktorwald
nicktorwald committed Dec 5, 2019
1 parent 4ba88fb commit dd73edd
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333 changes: 333 additions & 0 deletions src/main/java/org/tarantool/jdbc/EscapeSyntaxParser.java
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package org.tarantool.jdbc;

import static org.tarantool.jdbc.EscapedFunctions.Expression;
import static org.tarantool.jdbc.EscapedFunctions.FunctionExpression;
import static org.tarantool.jdbc.EscapedFunctions.FunctionSignatureKey;
import static org.tarantool.jdbc.EscapedFunctions.functionMappings;

import org.tarantool.util.SQLStates;
import org.tarantool.util.ThrowingBiFunction;

import java.sql.Connection;
import java.sql.SQLSyntaxErrorException;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.regex.Pattern;

/**
* Set of utils to work with JDBC escape processing.
* <p>
* Supported escape syntax:
* <ol>
* <li>Scalar functions (i.e. {@code {fn random()}}).</li>
* <li>Outer joins (i.e. {@code {oj "dept" left outer join "salary" on "dept_id" = 1412}}).</li>
* <li>Like escape character (i.e. {@code like '_|%_3%' {escape '|'}}).</li>
* <li>Limiting returned rows (i.e. {@code {limit 10 offset 20}}).</li>
* </ol>
* <p>
* Most of the supported expressions translates directly omitting escape borders.
* In this way, {@code {fn abs(-5)}} becomes {@code abs(-5)}} or {@code {limit 10 offset 50}}
* becomes {@code limit 10 offset 50} and so on. There are exceptions in case of scalar
* functions where JDBC functions may not match exactly with Tarantool ones (for example,
* JDBC {@code {fn rand()}} function becomes {@code random()} supported by Tarantool.
*/
public class EscapeSyntaxParser {

/**
* Pattern that covers function names described in JDBC Spec
* Appendix C. Scalar functions.
*/
private static final Pattern IDENTIFIER = Pattern.compile("[_a-zA-Z][_a-zA-Z0-9]+");

private final SQLConnection jdbcContext;

public EscapeSyntaxParser(SQLConnection jdbcContext) {
this.jdbcContext = jdbcContext;
}

/**
* Performs escape processing for SQL queries. It translates
* sql text with optional escape expressions such as {@code {fn abs(-1)}}.
*
* <p>
* Comments inside SQL text can be eliminated as parsing goes using preserveComments
* flag. Hence, Comments inside escape syntax are always omitted regardless of
* the flag, though.
*
* @param sql SQL text to be processed
*
* @return native SQL query
*
* @throws SQLSyntaxErrorException if any syntax error happened
*/
public String translate(String sql) throws SQLSyntaxErrorException {
StringBuilder nativeSql = new StringBuilder(sql.length());
StringBuilder escapeBuffer = new StringBuilder();
StringBuilder activeBuffer = nativeSql;
LinkedList<Integer> escapeStartPositions = new LinkedList<>();

int i = 0;
while (i < sql.length()) {
char currentChar = sql.charAt(i);
switch (currentChar) {
case '\'':
case '"':
int endOfString = seekEndOfRegion(sql, i, "" + currentChar, "" + currentChar);
if (endOfString == -1) {
throw new SQLSyntaxErrorException(
"Not enclosed string literal or quoted identifier at position " + i,
SQLStates.SYNTAX_ERROR.getSqlState()
);
}
activeBuffer.append(sql, i, endOfString + 1);
i = endOfString + 1;
break;

case '/':
case '-':
int endOfComment;
if (currentChar == '/') {
endOfComment = seekEndOfRegion(sql, i, "/*", "*/");
if (endOfComment == -1) {
throw new SQLSyntaxErrorException(
"Open block comment at position " + i, SQLStates.SYNTAX_ERROR.getSqlState()
);
}
} else {
endOfComment = seekEndOfRegion(sql, i, "--", "\n");
if (endOfComment == -1) {
endOfComment = sql.length() - 1;
}
}
if (i == endOfComment) {
activeBuffer.append(currentChar);
i++;
} else {
i = endOfComment + 1;
}
break;

case '{':
escapeStartPositions.addFirst(escapeBuffer.length());
escapeBuffer.append(currentChar);
activeBuffer = escapeBuffer;
i++;
break;

case '}':
Integer startPosition = escapeStartPositions.pollFirst();
if (startPosition == null) {
throw new SQLSyntaxErrorException(
"Unexpected '}' at position " + i,
SQLStates.SYNTAX_ERROR.getSqlState()
);
}
escapeBuffer.append(currentChar);
processEscapeExpression(escapeBuffer, startPosition, escapeBuffer.length());
if (escapeStartPositions.isEmpty()) {
nativeSql.append(escapeBuffer);
escapeBuffer.setLength(0);
activeBuffer = nativeSql;
}
i++;
break;

default:
activeBuffer.append(currentChar);
i++;
break;
}
}

if (!escapeStartPositions.isEmpty()) {
throw new SQLSyntaxErrorException(
"Not enclosed escape expression at position " + escapeStartPositions.pollFirst(),
SQLStates.SYNTAX_ERROR.getSqlState()
);
}
return nativeSql.toString();
}

/**
* Parses text like {@code functionName([arg[,args...]])}.
* Arguments are not parsed recursively and saved as-is.
*
* <p>
* In contrast to SQL where function name can be enclosed by double quotes,
* it is not supported within escape syntax.
*
* @param functionString text to be parsed
*
* @return parsed result containing function name and its parameters, if any
*
* @throws SQLSyntaxErrorException if any syntax errors happened
*/
private FunctionExpression parseFunction(String functionString) throws SQLSyntaxErrorException {
int braceNestLevel = 0;
String functionName = null;
List<String> functionParameters = new ArrayList<>();
int parameterStartPosition = 0;

int i = 0;
boolean completed = false;
while (i < functionString.length() && !completed) {
char currentChar = functionString.charAt(i);
switch (currentChar) {
case '\'':
case '"':
i = seekEndOfRegion(functionString, i, "" + currentChar, "" + currentChar) + 1;
break;

case '(':
if (braceNestLevel++ == 0) {
functionName = functionString.substring(0, i).trim().toUpperCase();
if (!IDENTIFIER.matcher(functionName).matches()) {
throw new SQLSyntaxErrorException(
"Invalid function identifier '" + functionName + "'", SQLStates.SYNTAX_ERROR.getSqlState()
);
}
parameterStartPosition = i + 1;
}
i++;
break;

case ')':
if (--braceNestLevel == 0) {
// reach a function closing brace
// parse the last possible function parameter
String param = functionString.substring(parameterStartPosition, i).trim();
if (!param.isEmpty()) {
functionParameters.add(param);
} else if (!functionParameters.isEmpty()) {
throw new SQLSyntaxErrorException(
"Empty function argument at " + (functionParameters.size() + 1) + " position",
SQLStates.SYNTAX_ERROR.getSqlState()
);
}
completed = true;
}
i++;
break;

case ',':
if (braceNestLevel == 1) {
// reach the function argument delimiter
// parse the argument before this comma
String param = functionString.substring(parameterStartPosition, i).trim();
if (param.isEmpty()) {
throw new SQLSyntaxErrorException(
"Empty function argument at " + (functionParameters.size() + 1) + " position",
SQLStates.SYNTAX_ERROR.getSqlState()
);
}
parameterStartPosition = i + 1;
functionParameters.add(param);
}
i++;
break;

default:
i++;
break;
}
}

if (functionName == null || !completed) {
throw new SQLSyntaxErrorException(
"Malformed function expression '" + functionString + "'", SQLStates.SYNTAX_ERROR.getSqlState()
);
}
if (i < functionString.length()) {
String tail = functionString.substring(i).trim();
if (!tail.isEmpty()) {
throw new SQLSyntaxErrorException(
"Unexpected expression '" + tail + "' after a function declaration",
SQLStates.SYNTAX_ERROR.getSqlState()
);
}
}
return new FunctionExpression(functionName, functionParameters);
}

/**
* Handles an escape expression. All expression substitutes are applied to
* the passed {@code buffer} parameter. In case of {@code fn}, the function
* name is case-insensitive.
*
* @param buffer buffer containing current escape expression
* @param start start position of the escape syntax in the buffer, inclusive
* @param end end position of the escape syntax in the buffer, exclusive
*
* @throws SQLSyntaxErrorException if any syntax error happen
*/
private void processEscapeExpression(StringBuilder buffer, int start, int end)
throws SQLSyntaxErrorException {
if (buffer.charAt(start) != '{' || buffer.charAt(end - 1) != '}') {
return;
}
int startExpression = seekFirstNonSpaceSymbol(buffer, start + 1);
int endExpression = seekLastNonSpaceSymbol(buffer, end - 2) + 1;

if (substringMatches(buffer, "fn ", startExpression)) {
FunctionExpression expression = parseFunction(buffer.substring(startExpression + 3, endExpression));
ThrowingBiFunction<FunctionExpression, Connection, Expression, SQLSyntaxErrorException> mapper =
functionMappings.get(FunctionSignatureKey.of(expression.getName(), expression.getParameters().size()));
if (mapper == null) {
throw new SQLSyntaxErrorException(
"Unknown function " + expression.getName(),
SQLStates.SYNTAX_ERROR.getSqlState()
);
}
buffer.replace(start, end, mapper.apply(expression, jdbcContext).toString());
} else if (substringMatches(buffer, "oj ", startExpression)) {
buffer.replace(start, end, buffer.substring(startExpression + 3, endExpression));
} else if (substringMatches(buffer, "escape ", startExpression)) {
buffer.replace(start, end, buffer.substring(startExpression, endExpression));
} else if (substringMatches(buffer, "limit ", startExpression)) {
buffer.replace(start, end, buffer.substring(startExpression, endExpression));
} else {
throw new SQLSyntaxErrorException("Unrecognizable escape expression", SQLStates.SYNTAX_ERROR.getSqlState());
}
}

/**
* Looks for the end of the region defined by its start and end
* substring patterns.
*
* @param text search text
* @param position start position in text to search the region, inclusive
* @param startRegion pattern of the region start
* @param endRegion pattern of the region end
*
* @return found position of the region end, inclusive. Start position if the region start
* pattern does not match the text start position and {@literal -1} if the
* region end is not found.
*/
private int seekEndOfRegion(String text, int position, String startRegion, String endRegion) {
if (!text.regionMatches(position, startRegion, 0, startRegion.length())) {
return position;
}
int end = text.indexOf(endRegion, position + startRegion.length());
return end == -1 ? end : end + endRegion.length() - 1;
}

private boolean substringMatches(StringBuilder text, String substring, int start) {
return text.indexOf(substring, start) == start;
}

private int seekFirstNonSpaceSymbol(StringBuilder text, int position) {
while (position < text.length() && Character.isWhitespace(text.charAt(position))) {
position++;
}
return position;
}

private int seekLastNonSpaceSymbol(StringBuilder text, int position) {
while (position > 0 && Character.isWhitespace(text.charAt(position))) {
position--;
}
return position;
}

}
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